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UNIVERSITY  OF  CALIFORNIA. 

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intend  this  book  to  be  sold  to  the  Public 
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The  Encyclopaedia  of 
Municipal  and  Sanitary  Engineering 


The    Encyclopaedia    of 

Municipal  and  Sanitary 
Engineering 

A  HANDY   WORKING   GUIDE    IN   ALL  MATTERS   CONNECTED 
WITH   MUNICIPAL   AND   SANITARY  ENGINEERING  AND 

Administration 

EDITED   BY 

W.    H.    MAXWELL    A.M.Inst.C.E. 


Borough    and    Waterworks    Engineer,    Tunbridge    Wells 
Past  President  of  the  Institute  of  Sanitary  Engineers,  &c. 


J.    T.    BROWN    M.R.San.Inst 

Editor  of  "The  Sanitary  Record" 


NEW     YORK 

D.     VAN      NOSTRAND     COMPANY 
23     MURRAY    AND   27     WARREN    STREETS 

1910 


PREFACE 

IN  the  present  day  the  constant  addition  to  the  duties  and  responsibilities  of  local 
authorities  imposes  upon  them  many  new  departments  of  work,  and  at  the  same  time 
intensifies  existing  powers  and  obligations  in  all  matters  of  municipal  and  sanitary 
engineering. 

It  has  thus  become  well-nigh  impossible  for  those  interested  in  local  administration 
to  keep  themselves  informed,  even  in  general  outline,  on  the  many  and  varied  subjects 
to  which  attention  is  now  demanded  by  the  State.  The  requisite  information  can  only  be 
gained  by  the  expenditure  of  time,  labour,  and  money  in  searching  through  a  mass  of 
literature  mainly  in  the  form  of  papers  and  reports. 

For  the  first  time  such  information  is  presented  in  dictionary  form,  convenient 
for  immediate  reference.  To  further  facilitate  this,  the  longer  articles  are  divided  into 
sections,  the  order  of  which,  as  well  as  the  pith  and  scope  of  the  article,  being  shown  by 
a  brief  index  at  the  head.  Acts  of  Parliament  affecting  the  various  subjects  dealt  with 
are  quoted  when  necessary,  and  a  careful  system  of  cross-referencing  has  been  followed  in 
order  that  the  reader  may  rapidly  acquire  information  on  the  cognate  aspects  of  a  subject. 

The  work  has  been  prepared  by  many  leading  experts,  whose  experience  in  the 
matters  with  which  they  deal  is  well  known ;  but  the  information  has  been  gathered  from 
all  parts  of  the  world,  and  the  Editors  tender  cordial  thanks  to  all  those  engineers  and 
local  authorities  who  have  so  readily  placed  the  results  of  practical  experience  at  their 
disposal. 

The  Editors  desire  to  record  the  assistance  they  have  received  from  Mr.  G.  Cadogan 
Piothery  and  Mr.  C.  F.  Tweney  in  planning  and  editing  "  The  Encyclopaedia." 


214838 


LIST    OF    CONTRIBUTORS 


ADAMS,  Professor  HENRY,  M.Inst.C.E.,  M.I.Mech.E., 
F.S.I.,  F.R.San.L 

ADY,  C.  E.,  M.J.I. 

ANGEL,  E,  J.,  M.Inst.C.E.,  A.E.I.B.A.,  Borough 
Engineer  and  Surveyor,  Bermondsey. 

BOYD,  E.  A.,  M.S.A. 

BURNE,  E.  LANCASTER,  A. M.Inst.C.E.,  A.M.I.Mech.E., 

Consulting  Engineer. 

CHAMBERS,  SIDNEY  H.,  Surveyor  Hampton  Urban 
District  Council. 

DEFRIES,  WOLF,  B.A.  (Lond.),  M.I.Mech.E. 

DIBDIN,  W.  J.,  E.I.C.,  F.C.S.,  formerly  Chemist  and 
Superintending  Gas  Engineer,  London  County 
Council. 

FIRTH,  Lieut.-Col.  E.  H.,  E.A.M.C. 

FOWLER,  Dr.  GILBERT  J.,  F.I.C.,  Consulting  Chemist 
to  the  Manchester  Corporation  Eivers  Committee. 

FREEMAN,  ALBERT  C.,  M.S.A. 

FREEMAN,  W.  MARSHALL,  of  the  Middle  Temple, 
Barrister-at-Law. 

FRETWELL,  W.  E.,  Lecturer  on  Plumbing  and 
Sanitary  Science,  L.C.C.  School  of  Building. 

GARFIELD,  JOSEPH,  A.M.Inst.C.E.,  Sewerage  Engineer, 
Bradford. 

HOBART,  H.  M.,  M.Inst.C.E.,  M.I.E.E.,  &c. 

HOLMES,  BASIL,  Secretary  Metropolitan  Public 
Gardens  Association. 

JENNINGS,  ARTHUR  SEYMOUR,  Editor  of  'The  Decorator. 
JENSEN,  GERARD  J.  G.,  C.E.,  Consulting  Engineer. 

KENWOOD,  H.  E.,  M.B.,  B.S.,  D.P.H.,  Professor  of 
Hygiene  and  Public  Health,  University  College, 
London. 


LATHAM,  FRANK,  Borough  Engineer  and  Surveyor, 
Penzance. 

MARRIOTT,  W.,  Assistant  Secretary  Eoyal  Meteoro- 
logical Society. 

MARTIN,  ARTHUR.  J.,  M.Inst.C.E.,  Consulting 
Engineer. 

MAXWELL,  W.  H.,  Assoc.M.Inst.C.E.,  Borough  and 
Waterworks  Engineer,  Tunbridge  Wells. 

MOOR,  C.  G.,  M.A.,  F.I.C.,  F.C.S.,  Public  Analyst 
for  the  County  of  Dorset  and  the  Borough  of 
Poole. 

OWRNS,  Dr.  JOHN  S.,  A.M.Inst.C.E.,  M.E.San.I. 
PARTRIDGE,  W.,  F.I.C. 

PORDAGE,  A.,  Firemaster,  City  of  Edinburgh. 
EIDEAL,  S.,  D.Sc.(Lond.),  F.I.C.,  F.E.San.I. 

EOTHERY,  G.  CADOGAN,  of  The  'Sanitary  Record  and 
The  Electrical  Engineer. 

SHENTON,  H.  C.  H.,  M.S.E.,  Consulting  Engineer. 

SOMMERVILLE,  DAVID,  B.A.,  M.D.,  D.P.H.,  Lecturer 
on  Public  Medicine,  King's  College,  London. 

THOMPSON,  GIBSON,  Editor  of  The  Surveyor. 
THOMPSON,  Alderman  WILLIAM. 

THRESH,  JOHN  C.,  M.D.,  D.Sc.,  Medical  Officer  of 
Health  for  the  County  of  Essex. 

TURNER,  SYDNEY  G.,  Assoc.M.Inst.C.E.,  Barrister- 
at-Law. 

WALLIS,  G.  WHITE,  F.S.S.,  Secretary  and  Director, 
Eoyal  Sanitary  Institute,  London. 

WATSON,  JOHN  D.,  M.Inst.C.E.,  Engineer  to  the 
Birmingham,  Tame  and  Eea  District  Drainage 
Board. 

WEBBER,  W.  H.  Y.,  C.E.,  Consulting  Engineer. 

WINSLOW,  C.  E.  A.,  Massachusetts  Institute  of 
Technology,  Boston,  U.S.A. 


THE  ENCYCLOPAEDIA 


OF 


MUNICIPAL    AND    SANITAKY 
ENGINEEEING. 


Abattoirs. — Acts  of  Parliament — Site — 
Accommodation  —  Lairs  and  Pens  —  Slaughter- 
houses —  Tripe  -  Dressing  Department  -  -  Pig 
Department — Refuse  Removal — Water  Purifica- 
tion— Inspection  Lairs — Hospital  for  Diseased 
Animals — Entrance  Lodge — Cost. 

ACTS  OF  PARLIAMENT. — The  following  are 
the  Acts  of  Parliament  relating  to  slaughter- 
houses :  Markets  and  Fairs  Clauses  Act,  1847  ; 
Towns  Improvement  Clauses  Act,  1847  ; 
Public  Health  Act,  1875;  Public  Health 
(London)  Act,  1891  ;  Public  Health  Act,  1908. 

The  clause  in  the  Public  Health  Act,  1875, 
reads  as  follows  : — 

"Any  urban  authority  may,  if  they  think 
fit,  provide  slaughter-houses,  and  they  shall 
make  bye-laws  with  respect  to  the  manage- 
ment and  charges  for  the  use  of  any  slaughter- 
houses so  provided."  "  For  the  purposes  of 
enabling  any  urban  authority  to  regulate 
slaughter-houses  within  their  district,  the 
provisions  of  the  Towns  Improvement  Clauses 
Act,  1847,  with  respect  to  slaughter-houses, 
shall  be  incorporated  with  this  Act."  "  Nothing 
in  this  section  shall  prejudice  or  affect  any 
rights,  powers,  or  privileges  of  any  persons 
incorporated  by  any  local  Act  passed  before  the 
passing  of  the  Public  Health  Act,  1848,  for 
the  purpose  of  making  and  maintaining 
slaughter-houses."  (38  &  39  Viet.  c.  55,  s. 
160.) 

SITE  is  the  foremost  consideration,  and 
the  place  selected  should  be  near  the  cattle 
market,  or  in  conjunction  with  it,  so  as  to 
prevent  the  long  journey  through  the  town 
for  the  cattle,  to  inconvenience  them  a,s 

M.S.E.  ;  -r 


little  as  possible,  and  to  prevent  the  loss  of 
weight  which  an  animal  suffers  on  a  long 
journey.  The  site  should  also  be  either  near 
or  alongside  a  railway  siding  or  waterway 
wharf,  for  precisely  similar  reasons.  For  the 
easy  and  cheap  conveyance  of  the  dead  meat 
to  the  butchers'  shops  and  cold  storage,  it  will 
be  necessary  to  have  the  slaughter-house  in 
as  central  a  position  as  possible.  The  approach 
roads  to  the  site  should  be  as  wide  as  possible, 
allowing  the  cattle  an  easy  passage  to  the 
lairs.  The  laying  out  or  planning  of  the 
site  is  a  very  important  point,  and  care 
must  be  exercised  to  group  the  whole  accom- 
modation for  each  class  of  cattle.  There 
appears  to  be  little  doubt  that  the  large 
slaughter-house  is  much  the  better  idea ;  the 
system  of  having  a  number  of  small  slaughter- 
houses, each  to  be  used  by  one  butcher, 
having  many  disadvantages  and  lending  itself 
to  serious  objections,  owing  to  the  inability 
to  properly  inspect  the  meat  before  it  is 
removed.  The  planning  and  construction  of 
the  two  types  are  practically  similar ;  and 
we  will  confine  ourselves  to  the  single  large 
slaughter-house  and  the  necessary  buildings 
adjoining. 

ACCOMMODATION. — In  designing  a  public 
slaughter-house,  it  is  usual  to  provide  for  the 
following  accommodation  :  (1)  Lairs  for  cattle ; 
(2)  pens  for  sheep  ;  (3)  slaughter-house ;  (4) 
tripe  -  dressing  department ;  (5)  pig  -  killing 
department,  consisting  of  sties,  covered  yard, 
scalding-house,  tripe  -  dressing  department, 
and  a  meat-dressing  department ;  (6)  cold  stor- 
age (sometimes);  (7)  refuse  receptacle  and 


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ENCYCLOPEDIA   OF 


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destructor ;  (8)  water  purification  plant ;  (9) 
inspection  lairs  for  cattle  before  being 
slaughtered ;  (10)  hospital  for  cattle  under 
observation,  with  slaughter-house  attached ; 
(11)  porter's  or  superintendent's  lodge  and 
administration  block,  including  office  and 
weighing  machine. 

It  will  be  seen  that  a  well-appointed 
abattoir  contains  many  departments  ;  and  it 
will  therefore  be  impossible  in  the  present 
article  to  go  fully  into  the  details  of  each 
department.  It  is  proposed,  however,  to  bring 
out  the  general  principles  in  planning,  and 
state  the  requirements  necessary  in  this  class 
of  building.  We  will  now  deal  briefly  with 
each  portion  of  the  accommodation,  proceeding 
in  the  order  set  out  above. 

1.  LAIRS  FOR    CATTLE. — The  places  where 
the    animals   are   rested    previous    to    being 
killed.      They  should  be  placed  as   close  as 
possible  to  the  slaughter-house,  but  should  not 
enter   directly  into  it,  but  into  a  passage  or 
corridor    leading    into    the    slaughter-house. 
It  is  usual  to  make  the  lairs  of  sufficient  size 
to    accommodate  three    days'    meat   supply. 
The  paving   should   be    of    hard    impervious 
materials,  e.g.,  asphalte ;  but  in  the  corridor 
granite  setts  are  best,  as  the  beast  struggles 
when    he    "  smells     blood " ;    and    asphalte 
is    rather   too   slippery.      The  walls   for  six 
feet    from    the  floor    should    be    lined   with 
hard  smooth  material,  e.g.,  iron.     The  lairs 
must  be  well  ventilated,  lighted,  and  drained. 
The    upper    part   may   be   used  for  storage 
purposes.     In  the  lair,  water  and  hay  troughs 
should  be  fitted  for  feeding  purposes. 

2.  PENS  FOR  SHEEP. — These  should  be  con- 
structed and  arranged  in  an  exactly  similar 
manner  as  the  lairs  for  cattle. 

3.  THE  SLAUGHTER-HOUSE. — There  are  two 
systems  upon  which  this   may  be  designed : 
(a)   A  number  of  small  complete  slaughter- 
houses ;  (6)  one  large  hall.     The  latter  form 
ensures    much    more  cleanliness    and    more 
efficient  supervision  of  the  meat,  and  for  these 
reasons  alone  it  is  to  be  recommended.     The 
hall    should   be   large  enough    to    allow   for 
killing  three  days'  meat  supply  in  one  working 


day.  All  cattle,  large  and  small,  may  be 
killed  in  this  large  hall — also  sheep.  The  hall 
should,  where  possible,  face  the  north,  be  in 
close  connection  with  and  easy  of  access  to 
the  cold  storage,  tripe-dressing,  and  the  cattle 
lairs  and  sheep  folds.  Light  and  ventilation 
must  be  plentiful ;  and  protection  from  the 
heat  of  the  sun  is  very  necessary.  Floors 
should  be  of  hard,  impervious  material,  and 
walls  should  be  of  light  colour.  It  is  usual  to 
line  the  walls  for  a  height  of  six  feet  with 
white  glazed  bricks,  this  allowing  great  facilities 
for  cleansing.  Drainage  must  be  carefully 
considered,  no  gullies  or  gratings  being  per- 
missible in  the  slaughter-house.  The  floor 
should  have  a  good  fall  towards  the  large  doors 
through  which  the  dead  meat  will  be  carted. 
Along  the  side  wall  an  open  channel  should  be 
constructed,  delivering  on  to  gullies  outside 
the  building,  with  gratings  over,  to  prevent 
solids  entering  the  drain.  This  drain  should 
be  carried  to  the  water-purification  plant,  and 
the  contents  purified  before  being  turned  into 
the  town  sewer.  The  necessary  killing  rings 
must  be  placed  in  convenient  positions  in  the 
floor.  Doors  should  be  made  sliding,  not 
folding.  Water  should  be  laid  on  in  plentiful 
supplies,  stand-posts  being  erected  to  each 
"killing  bay."  The  walls  must  be  strong 
enough  to  carry  the  girders  which  support  the 
winches  and  necessary  hoisting  and  travelling 
gear.  The  necessary  lavatory  accommodation 
for  the  users  of  the  slaughter-house  must  be 
provided  near  by. 

4.  TRIPE  -  DRESSING      DEPARTMENT.  —  This 
should  be  provided  close  to,  and  opening  out 
of,  the  slaughter-house,  and  fitted  with  basins 
with  running  water,  scalding  coppers,  dressing 
and  scrubbing  tables,  and  hot  and  cold  water 
basins.  Steam  will  be  plentiful,  and  ventilation 
must  be  effective  to  carry  this  off.     Light  must 
also  be  plentiful.     The  floor  and  walls  must 
be  hard  and  washable,  and  similar  to  those  of 
the  slaughter-house. 

5.  PIG  KILLING  DEPARTMENT. — This  depart- 
ment is  quite  separate  from  the  other  portion 
of  the  abattoir,  and  consists  of : — (a)  Pig-sties 
for  each  butcher  capable  of  holding  three  days' 


ABA 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


ABA 


supply  of  pork,  adjoining  which,  and  separated 
by  a  gangway,  are  the  (b)  Killing  and  bleeding 
pens,  which  are  covered  over,  (c)  Scalding 
house,  which  is  close  to  the  killing  yard,  and 
must  be  provided  with  scalding  coppers  fed 
by  hot  water.  Hoisting  gear  on  travelling 
trolleys  should  be  provided,  by  which  the  dead 
pig  may  be  hoisted  over  the  copper,  plunged 
in,  and  then  run  on  to  the  dressing  house 
which  adjoins,  (d)  Dressing  house.  This 
should  be  provided  with  plenty  of  suspension 
hooks  on  which  to  hang  the  meat.  It  should 
adjoin,  or  be  close  by,  the  cold  storage,  so  that 
the  meat  may  be  transferred  to  this  part  for 
storage  after  being  dressed,  (e)  The  tripe- 
dressing  department,  adjoining  the  dressing 
house  should  be  fitted  up  in  a  similar 
manner  to  that  described  for  cattle.  Store 
room  for  tools,  dressing  rooms  for  butchers, 
and  lavatory  accommodation  should  also  be 
provided. 

6.  COLD    STOEAGE. — This   is  essentially  an 
advantage  for  the  private  butcher.     It  must 
be  in   close  proximity  to  the  cattle  and  pig 
slaughter-houses,  and  comprise  cold-producing 
machinery   room,    coal    stores,    boiler-house, 
and  annexes  or  antechambers.     It  should  be 
capable  of  holding  three  days'  supply  of  meat, 
open  direct  on  to  the  yard,  with  large  sliding 
doors,  and  be  so  lighted  that  light  is  obtained 
and  heat   excluded.     It  should   be  placed,  if 
possible,  on  the  north-eastern  side  of  the  site 
with  the  south  and  west  sides  adjoining  the 
slaughter-house,  or  some  part  of  the  buildings. 
Overhead  pulleys  travelling  on  rails  must  be 
provided  for  the  conveyance  of  meat.     All  the 
inside  faces  of  the  walls  should  be  lined  with 
glazed  bricks  or  tiles  for  the  full  height. 

7.  REFUSE   DISPOSAL. — Ample  means  must 
be  provided  for  the  disposal  of  the  refuse,  and 
the   most   effective   way   appears    to   be   the 
Pohlwil    apparatus  —  a    German     invention. 
This  system  has  been  fitted  up  in  duplicate  at 
the  City  of  London  abattoir,  Islington.     The 
process  is  as  follows: — The  machinery  consists 
of  a  steam-tight  cylinder  made  of  boiler  plates, 
and  fitted  with  hopper  inlet  and  outlet  with 
screw-down  cover,  steam  connections,  pressure 


gauge  and  safety  valve,  and  provided  inside 
with  steel  rollers.  All  the  diseased  carcases 
(which  must  be  cut  up),  including  skin,  bones, 
and  all  offal,  is  inserted  into  the  cylinder 
through  the  hoppers.  The  cover  is  then 
screwed  down  and  steam  injected  under 
pressure.  After  a  certain  time,  the  cylinder 
is  made  to  revolve  and  the  inside  cylinders 
also  revolve,  thus  crushing  up  the  whole  of 
the  contents  into  a  fine  brown  powder.  The 
cylinder  is  stopped,  the  cover  removed,  and 
the  apparatus  started  again  slowly,  when  the 
powder  falls  into  a  pit  below.  The  great 
advantage  of  this  system  is  that  all  the  refuse 
of  whatever  description  may  be  shot  into  the 
cylinder.  The  powder  may  be  sold  as  a 
manure  and  is  rich  in  fertilising  qualities. 

In  many  abattoirs  the  refuse  is  disposed  of 
either  by  burning  or  carting  away  in  wagons. 
In  any  case  the  building  used  must  be  isolated, 
but  in  a  central  position,  closed  and  well 
ventilated,  and  lighted  by  a  top  light.  Near 
this  may  be  placed  the  tripe-washing  troughs. 

8.  WATER    PURIFICATION    PLANT.  —  Before 
turning  the  contents  of  the  drains   into  the 
main  sewer  or  river  (if  one  adjoins  or  is  near 
the   building),  it   should   be   put   through   a 
purification  process. 

9.  INSPECTION  LAIRS. — Near  the  entrance  to 
the  abattoir  should  be  placed  inspection  lairs 
for  the  cattle  and  pigs,  so  that  they  may  be 
inspected  by  the  veterinary  surgeon  previous 
to  transit  to  the  "killing  lairs."     Suspected 
cattle  and  pigs  should  then  be  passed  on  to 
special  detention  lairs,  and  diseased  ones  on 
to  the  slaughter-house  and  premises  for  such. 

10.  HOSPITAL  FOE  DISEASED  ANIMALS. — This 
should   be   entirely  isolated   from   the   other 
building,  and  consist  of  lairs  and  slaughter- 
house, with   meat    store    attached,    so    that 
carcasses  which  are  discovered  to  be  diseased 
may  also  be  stored  in  it. 

11.  ENTRANCE    LODGE.  —  A    small    house 
should  be  provided  for  the  superintendent  of 
the   abattoir,    to   which   may  be   attached   a 
weigh    office,   office    for    medical    officer    or 
veterinary  surgeon,  meter-house   for   gas   or 
electric  light,  and  store  room  for  tools,  &c., 

3  B  2 


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ENCYCLOPEDIA   OF 


ABY 


and  near,  or  adjoining  the  offices,  should  be 
placed  the  w.c.  and  urinal  accommodation, 
and,  in  some  cases,  waiting  rooms  for  drovers 
and  cattle  dealers. 

COST. — This,  naturally,  varies  for  different 
towns.  Some  have  small  abattoirs,  which 
supply  the  needs,  whereas  others,  e.g.,  Birken- 
head,  have  one  on  a  very  extensive  scale. 

On  referring  to  the  returns  collected  from 
different  towns,  the  cost  appears  as  follows : — 
Preston  costs  about  lid.  per  head  of  population 
Birkenhead       „       2/6         „         ,,         ,, 
Carlisle  „       3/6         „         ,,         „ 

Leeds  „ 

Paisley  „ 

R.  H.  B. 

A.  B.  C.  Process  (Sewage  Treatment). 

— The  precipitants  used  in  this  process  are 
alum,  blood,  clay  and  charcoal.  The  blood  is 
now  omitted  and  it  is  probable  equal  results 
would  be  obtained  by  the  alum  alone.  The 
process  is  used  at  Aylesbury  and  Kingston-on- 
Thames.  A  "  native  guano "  is  made  from 
sewage  by  this  method  at  Aylesbury,  but 
there  is  considerable  difference  of  opinion  as 
to  the  commercial  value  of  the  product.  The 
effluent  is  reported  very  pure,  and  the  process 
appears  to  be  carried  on  without  nuisance. 
The  quantity  of  sludge  produced  is  considerable, 
and  at  Kingston  this  is  disposed  of  by  the 
Native  Guano  Company. 

Absolute-rest   precipitation  tanks.— 

This  type  of  tank  is  not  used  to  any  very  large 
extent  owing  to  the  amount  of  fall  and  tank 
accommodation  required.  The  "  continuous- 
flow  "  tank  is  more  generally  employed.  After 
settlement  in  the  absolute-rest  tank,  the  top 
water  is  gradually  drawn  off  by  floating  arms 
down  to  the  level  of  the  precipitated  sludge, 
the  latter  being  let  off  through  a  sludge- 
penstock.  With  quiescent  sedimentation, 
two  or  three  hours'  settlement  is  usually 
sufficient  to  yield  a  fairly  satisfactory  tank 
liquor.  The  tanks  should  be  used  in  parallel, 
and  the  sludge  should  be  frequently 
removed. 


Abyssinian  tube  wells. — These  consist 
of  iron  tubes  from  1^  in.  to  4  in.  diameter 
driven  into  the  ground  until  the  subsoil 
water  is  reached  for  the  purpose  of  quickly 
obtaining,  by  means  of  a  pump  fixed  at  the 
top,  a  temporary  supply  of  water.  Wells  of 
this  description  were  first  extensively  used 
during  the  Abyssinian  cam- 
paign, hence  the  name  by 
which  they  are  now  popularly 
known.  These  wells  are  also 
known  sometimes  as  Norton's 
tube  wells,  and  American  tube 
ivells.  The  iron  tubes  are 
driven  into  the  ground  in 
lengths  by  means  of  a 
"monkey  "  —  the  first  tube 
having  a  hard  steel  nozzle, 
the  lower  2  feet  of  the  sides 
of  the  tube  being  perforated. 
Successive  lengths  of  tube  are 
screwed  on  and  driven  until 
the  necessary  depth  is  reached. 
Such  tubes  have  been  satis- 
factorily put  down  to  as  much 
as  150  feet  depth,  but  the 
usual  limit  is  about  50  feet. 
The  most  suitable  strata  for 
obtaining  water  by  this  means 
are  the  chalk,  gravel,  and 
coarse  sand  where  well  satu- 
rated. The  system  is  not 
suitable  in  fine  sand,  clay  or 
marl,  and  the  tubes  cannot,  of  Abyssinian  Tube 

~\\T    ?1 

course,  be  driven  through  hard 
rock  beds.  After  the  tubes  have  been  driven 
and  water  has  been  reached  a  hand-pump  is 
attached  and  the  yield  of  the  well  and  quality  of 
the  water  tested.  Should  the  results  prove  un- 
satisfactory the  well  may  be  driven  deeper,  or 
the  tubes  withdrawn  and  redriven  at  another 
likely  site.  Abyssinian  tubes  are  sometimes 
advantageously  driven  at  the  bottom  of 
ordinary  sunk  wells  for  the  purpose  of  in- 
creasing the  yield.  Where  favourable  condi- 
tions exist,  a  driven  tube  well  affords  a  cheap, 
ready  and  safe  means  of  securing  temporary 
supplies.  The  quantity  of  water  obtainable 


ACC 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


ACE 


will  vary  greatly  according  to  the  conditions 
of  the  site,  nature  of  the  strata,  depth  of  well, 
and  capacity  of  the  pump,  but  if  favourably 
placed  a  1}  in.  diameter  well  may  be  expected 
to  yield  from  150  to  600  gallons  per  hour,  a 
2  in.  diameter  from  300  to  1,500  gallons,  and 
a  3  in.  diameter  from  500  to  2,500  gallons. 

The  cost  of  tube  wells  also  varies  according 
to  the  circumstances  to  be  dealt  with,  but 
under  ordinary  conditions  in  gravelly  ground 
a  1  j  in.  by  30  ft.  well  may  be  expected  to  cost 
about  £10,  or  7s.  per  foot  of  depth,  including 
all  expenses  of  labour,  materials  and  cartage. 
A  2  in.  by  30  ft.  wrell  would  cost  under  similar 
circumstances  about  £15,  or  10s.  per  foot 
of  depth.  W.  H.  M. 

Access  Pipe. — A  pipe  having  an  air-tight, 
removable  lid  or  a  manhole  giving  access  to 
the  interior  of  the  pipe  and  thence  to  the 
drain,  soil,  or  waste  pipe  upon  which  it  is 
fixed.  Such  pipes  are  most  usefully  provided 
at  bends  and  junctions  to  provide  means  for 
clearing  obstructions  and  for  cleaning  pur- 
poses. (See  also  CLEANING  EYE.) 

Accumulator  (hydraulic). — An  appli- 
ance for  storing  water  under  pressure, 
whereby,  very  heavy  work  may  be  accom- 
plished in  a  short  time.  It  consists  of  a  long 
vertical  cylinder  fitted  with  a  weighted  ram, 
which  works,  water-tight,  through  a  stuffing 
box  and  gland  at  the  top.  By  pumping  water 
into  the  bottom  of  the  cylinder  the  ram  with 
its  weight  is  raised,  and  the  pressure  due  to 
the  same  may  be  utilised  for  driving  hydraulic 
cranes,  lifts,  riveting  or  other  machines, 
where  the  work  is  of  an  intermittent  nature. 
The  water  supply  to  the  cylinder  is  auto- 
matically regulated  by  causing  the  weight  to 
strike  levers,  so  arranged  that  when  the 
cylinder  is  full  and  the  ram  at  the  top  of  its 
stroke,  the  forcing  pumps  are  stopped ;  when 
approaching  emptiness  through  the  use  of  the 
water,  the  pumps  are  started  again  by  the 
descent  of  the  ram. 

The  pressure  per  square  inch  will  be  equal 
to  the  total  weight  in  Ibs.,  including  that  of 


the  ram  and  the  connections  that  move  with 
it,  divided  by  the  cross-sectional  area  of  the 
ram  in  square  inches.  The  work  stored  in 
the  accumulator  is  equivalent  to  the  total 
weight  in  Ibs.  multiplied  by  the  height  in 
feet  through  which  it  is  raised ;  less  a  slight 
fractional  loss  in  each  case.  The  usual  work- 
ing pressure  for  cranes  and  lifts  is  about 
750  Ibs.,  for  machine  tools  1,500  Ibs.  and 
upwards  per  square  inch.  E.  L.  B. 

Acetylene. — Acetylene  is  a  colourless  gas, 
having  a  sweet  ethereal  smell.  As  ordinarily 
made  it  has  a  peculiar  penetrating  odour  like 
that  of  garlic,  due  to  the  impurities  which  it 
contains.  Chemically,  it  is  an  unsaturated 
hydro-carbon,  having  the  formula  CaHg,  and 
containing  by  weight  12  parts  of  carbon  to 
1  of  hydrogen.  Its  specific  gravity  is  0'9, 
that  of  air  being  taken  as  unity.  At  62°  F. 
1  cub.  ft.  =  0-0685  Ibs.  and  1  Ib.  =  14'6 
cub.  ft.  It  is  slightly  soluble  in  water, 
10  volumes  of  which  at  62°  F.  dissolve  11 
volumes  of  acetylene.  If,  however,  the  water 
is  saturated  with  salt,  20  volumes  of  it 
dissolve  only  1  of  the  gas. 

Acetylene  may  be  prepared  in  various  ways, 
but  for  practical  purposes  it  is  obtained  from 
calcium  carbide,  a  hard  greyish  substance, 
generally  of  a  fine  crystalline  texture,  which 
is  made  by  reducing  quicklime  with  coke  in 
the  electric  arc.  The  reaction  is  as  follows  : — 


CaO    + 
Quicklime.     Carbon. 


3  C    =     CaC2 
Calcium 
Carbide. 


CO 

Carbonic 
Oxide  Gas. 


The  specific  gravity  of  calcium  carbide  is 
2'22,  and  it  contains  five  parts  of  calcium 
to  three  of  carbon. 

When  calcium  carbide  is  brought  into  con- 
tact with  water,  the  following  double  decom- 
position takes  place  :— 

CaC2    +    H20    =      CaO     +      C2H2 

Calcium      1T7  ,          ^  .  , ,. 

Carlide       Water.     Quicklime.     Acetylene. 

The  quicklime  at  once  combines  with  the 
excess  of  water  to  form  slaked  lime,  Ca[HO]2. 
Theoretically,  the  quantity  of  water  required 


ACE 


ENCYCLOPAEDIA  OF 


ADA 


is  under  half  a  pint  per  pound  of  carbide,  but 
in  practice  a  pint  must  be  supplied.  Theoreti- 
cally also  1  Ib.  of  pure  carbide  should  give 
5'93  cub.  ft.  of  acetylene.  In  practice  5 
cub.  ft.  is  a  good  output ;  but  yields  up  to 
5*22  cub.  ft.  are  claimed. 

Acetylene  burns  with  a  brilliant  and  steady 
flame,  and  during  the  past  ten  years  has  come 
into  extensive  use  for  small  lighting  installa- 
tions. In  this  country  alone  some  300  forms  of 
generator  have  been  patented,  of  which  about 
one-tenth  have  been  placed  on  the  market.  A 
good  generator  should  work  at  a  low  tempera- 
ture and  a  low  pressure,  and  should  effect  a 
complete  decomposition  of  the  carbide,  so  as 
to  give  a  maximum  yield  of  gas.  The  latter 
may  be  generated  either  by  allowing  the  water 
to  drip  on  to  the  carbide,  or  by  dropping  the 
carbide  in  small  pieces  into  the  water,  the 
latter  method  possessing  several  important 
advantages.  Two  or  three  horizontal  screens 
or  gratings  should  be  placed  in  the  water  to 
catch  the  carbide,  and  prevent  it  from  drop- 
ping into  the  lime  sludge  which  settles  at  the 
bottom. 

Generators  are  either  "  automatic "  or 
"  non-automatic,"  the  former  making  the  gas 
only  as  required  for  use,  and  the  latter  con- 
tinuously. With  non-automatic  generators 
holders  must  be  provided  to  store  the  gas 
whenever  the  demand  falls  short  of  the 
supply.  This  form  of  generator  is  to  be 
preferred. 

Commercial  calcium  carbide  is  never  pure, 
and  the  resulting  gas  likewise  contains  traces 
of  other  substances  ;  the  chief  impurities  being 
phosphuretted  and  sulphuretted  hydrogen  and 
ammonia.  The  gas  should,  therefore,  be 
passed  through  a  purifier  before  use. 

Acetylene  has  a  high  calorific  value,  namely, 
1,504  B.  T.  U.  per  cubic  foot,  exclusive  of  the 
heat  latent  in  the  water  vapour  due  to  com- 
bustion. A  cubic  foot  of  the  gas  requires  for 
complete  combustion  about  12  cub.  ft.  of  air, 
the  products  being  carbonic  acid  gas,  water, 
and  nitrogen.  A  mixture  of  acetylene  and 
air  is  explosive  when  the  proportion  of  the 
former  is  anywhere  between  3  per  cent,  and 


82  per  cent,  of  the  whole.  The  gas  alone 
will  explode  when  subjected  to  sudden  com- 
pression. 

Composition  tubing  should  never  be  used 
to  carry  acetylene,  and  the  pipes  should  be  of 
the  best  iron  barrel,  not  less  than  f  in.  in  dia- 
meter. The  pipes  may  be  somewhat  smaller 
than  for  coal  gas. 

When  acetylene  is  burnt  in  ordinary  gas- 
burners  the  flame  smokes,  and  large  quantities 
of  soot  are  deposited.  The  best  results  are 
obtained  from  special  burners  with  steatite 
tips,  so  formed  that  the  gas  is  shielded  from 
the  hot  nipple  by  a  layer  of  air.  The  flame 
is  small,  white,  and  intensely  bright,  and 
owes  its  .luminosity  to  the  incandescent  par- 
ticles of  carbon  which  it  contains.  The  amount 
of  light  obtained  from  acetylene  varies  with 
the  make  and  size  of  the  burner,  ranging 
from  24  candles  per  cubic  foot  with  burners 
consuming  |  cub.  ft.  per  hour  to  40  or  48 
candles  with  1  cub.  ft.  burners.  The  larger 
burners  are,  therefore,  the  more  economical. 
For  equal  volumes  acetylene  gives  many  times 
as  much  light  as  coal  gas  burnt  in  a  flat  flame 
burner,  and  from  1J  to  2J  times  as  much  as 
coal  gas  used  with  a  good  incandescent  mantle. 
Light  for  light  it  consumes  more  oxygen,  and 
evolves  more  COs  and  heat  than  an  incan- 
descent gas-burner,  but  very  much  less  of 
each  than  the  old  flat  flame  burner  with  coal 
gas. 

With  calcium  carbide  at  its  present  price 
acetylene  cannot  compete  with  coal  gas  used 
with  Welsbach  mantles ;  but  its  brilliancy  and 
convenience  will  ensure  its  adoption  in  many 
situations  where  coal  gas  is  not  obtainable. 

A.  J.  M. 

Adams'  Sewage  Lift. — This  is  an  appa- 
ratus in  which  high-level  sewage  is  applied 
to  the  work  of  raising  low-level  sewage  to 
an  intermediate,  or  middle  level,  intercept- 
ing sewer.  High-level  sewage  enters  the 
"  flush  tank,"  which  discharges  its  contents 
through  a  siphon,  followed  by  a  drop-pipe, 
into  the  "  air-cylinder "  shown  below,  thus 
displacing  the  air  contained  in  the  latter,  and 


ADA 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


AER 


forcing  it  through  an  "  air  pipe,"  which  con- 
veys it  to  the  "forcing  cylinder"  or  "ejector" 
situated  some  distance  away  in  the  low-level 
district.  This  air  is  there  utilised  to  drive 
out  the  liquid  contents  of  the  "  forcing 
cylinder  "  through  the  rising  main  shown  in 
the  figure.  After  having  been  thus  lifted  the 
sewage  gravitates  to  the  nearest  middle-level 
intercepting  sewer.  The  "  air  cylinder,"  after 
having  been  charged  with  the  liquid  contents 
from  the  "flush  tank,"  is  emptied  by  means 


the  height  of  the  lift,  &c.,  from  60  per  cent, 
up  to  500  per  cent.,  or  more  for  .high  lifts. 
The  system  is  also  applicable  to  raising 
sewage  of  underground  conveniences,  base- 
ments situated  below  sewer  level,  and  such 
like.  It  is  in  operation  at  Douglas,  Ilkley, 
Bowness,  Crayford,  and  other  places. 

Aerating  Tiles  (for  Bacterial  Bed 
Floors). — Aerating  floors  are  most  satis- 
factorily formed  by  constructing  a  floor  of 


AIR  CHAMBER  OR  POWER  STATION 
SITUATED  IN  HIGH  LEVEL  DISTRICT. 


INTERCEPTING  SEWER 

SITUATED  IN  MIDDLE  LEVE 

DISTRICT 


SEWAGE  EJECTING  OR  FORCING  CHAMBER 
SITUATED  IN  LOW  LEVEL  DISTRICT. 


Adams'  Sewage  Lift. 


of  a  siphon  shown  in  the  illustration,  and 
thus  prepared  ready  for  the  next  charge  from 
the  "flush  tank."  The  liquid  delivered  by 
the  siphon  from  the  "  air  cylinder  "  and  the 
sewage  from  the  rising  main  off  the  ejector  are 
both  delivered  by  gravitation  to  the  middle- 
level  intercepting  sewer. 

Where  high-level  sewage  is  not  available 
the  town  water  supply  is  sometimes  used  to 
give  the  necessary  head  for  creating  the 
requisite  pressure  of  air,  but  this  obviously 
adds  to  the  working  cost  of  the  system.  The 
quantity  of  liquid  used  to  raise  a  given  volume 
of  sewage  varies  according  to  local  conditions, 


concrete  6  in.  or  9  in.  thick,  according  to  the 
nature  of  the  foundation,  and  then  overlaying 
the  same  with  a  false  or  hollow  floor  of 
aerating  tiles. 

Such  a  floor  affords  the  best  opportunities 


FIG.  1. — Ames'  Aerating  Tile  for 
Bacteria  Beds. 


AER 


ENCYCLOPEDIA   OF 


AER 


FIG.  2.— Mansfield 
Aerating  Tile. 


for  the  thorough  and  uniform  aeration  of  the. 
superincumbent  filtering  medium,  which  is 
now  recognised  to  be  an  essential  feature  in 
the  efficient  working  of  bacterial  methods  of 
purification.  The  tiles 
now  used  in  this  con- 
nection are  of  great 
variety  of  design,  but  all 
have  a  similar  object  in 
providing  a  strong  open 
flooring  so  as  to  admit 
of  the  free  circulation  of  air  and  at  the  same 
time  afford  adequate  support  for  the  superin- 
cumbent filtering  materials.  The  three  tiles 
illustrated  are  respectively  of  Ames',  Mans- 
field's, and  Stiffs  pattern,  but  there  are  many 
other  varieties.  They  are  usually  made  of  stone- 
ware or  hard  burnt  Staffordshire  clays,  and, 
though  they  need  to  be  of  ample  strength, 
should  not  be  heavier  than  absolutely  neces- 
sary, otherwise  the  cost  of  carriage  will  render 


FlG.  3. — Stiff's  Aeration  Drainage  Channels, 

the  flooring  expensive.  The  "  Mansfield  "  tile 
is  simple  and  efficient,  and,  in  the  writer's 
experience,  costs  from  2s.  6d.  to  2s.  9d.  per 
square  yard  laid  complete. 

Aerobic  and  Anaerobic  (Treatment  of 
Sewage). — These  terms,  which  are  applied 
to  two  different  classes  of  bacteria,  simply 
mean  "  living  with  air  "  and  "  living  without 
air."  In  1861  Pasteur  discovered  that  many 
bacteria  could  live,  and  even  set  up  active  fer- 
mentation, in  the  absence  of  oxygen,  and  he, 
therefore,  gave  these  organisms  the  name  of 
anaerobes.  His  statements,  being  soon  cor- 
roborated, resulted  in  the  classification  of 
bacteria  into  two  groups — the  aerobes  and  the 


anaerobes.  To  the  aerobes  are  due  the  con- 
version of  urea  into  ammonia,  and  ammonia 
into  nitrate.  To  the  anaerobes  is  attributed 
the  decomposition  of  cellulose  and  allied 
substances  with  evolution  of  marsh  gas,  the 
removal  of  oxygen  from  nitrates  with  simul- 
taneous oxidation  of  organic  matter,  and  the 
decomposition  of  complex  organic  matter,  with 
production  of  ammonia,  hydrogen,  and  other 
substances. 

In  sewage  purification  the  work  of  the 
anaerobic  bacteria  is  mostly  done  in  the 
sewers  and  in  the  septic  tank,  whilst  that  of 
the  aerobic  class  is  confined  mainly  to  the 
percolating  beds.  In  contact  beds  both  aerobic 
and  anaerobic  conditions  obtain  according  to 
the  alternating  periods  of  rest  and  work. 

Fischer  in  "  Structure  and  Functions  of 
Bacteria  "  states  that  in  the  aerobic  bacteria 
the  process  of  respiration  is  the  same  as  in  all 
ordinary  organisms.  They  absorb  oxygen  and 
with  it  break  up  non-nitrogenous  bodies,  such 
as  glycerine  or  sugar,  into  carbonic  acid  and 
water.  They  are  also  able,  like  plants  and 
animals,  to  assimilate  nitrogenous  substances, 
such  as  peptones  and  amido  compounds, 
although  with  less  gain  of  energy  and  less 
easily  than  they  can  carbonaceous  bodies. 
Many  of  the  aerobic  bacteria  are  totally  unable 
to  live  without  oxygen,  and  when  deprived  of 
it  die,  as  would  a  mouse  in  pure  hydrogen. 
They  are  exclusive,  or  obligatory  aerobes. 
Contrasted  with  the  obligatory  aerobic  bacteria 
we  have  the  obligatory  anaerobic  forms,  which 
thrive  only  in  the  absence  of  oxygen,  small 
traces  of  this  gas  being  sufficient  to  inhibit 
growth.  Between  these  extremes  there  is  a 
great  host  of  bacteria  representing  every 
gradation  between  the  two  modes  of  life. 
These  are  the  facultative  anaerobes,  which, 
while  growing  best  with  a  plentiful  supply  of 
oxygen,  are  nevertheless  able  to  exist  with  a 
very  small  amount,  and  even  with  none  at  all, 
although  in  this  case  their  vitality  is  often 
much  impaired.  Anaerobic  bacteria,  both 
obligatory  and  facultative,  are  found  every- 
where in  Nature  where  the  air  cannot  penetrate, 
or  where  it  is  replaced  by  other  gases  in  the 


8 


AFT 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


AIR 


deeper  layers  of  the  soil ;  for  instance,  in  the 
mud  of  rivers  and  standing  waters,  or  the 
ooze  of  the  sea  bottom,  and  in  manure.  In 
all  such  places  anaerobic  bacteria  are  the  prin- 
cipal, and  often  the  only,  forms  of  life,  and 
by  the  fermentative  and  putrefactive  processes 
they  set  up  they  effect  the  disintegration  and 
removal  of  dead  animals  and  plants. 

W.  H.  M. 

After-flush. — A  small  quantity  of  flush- 
ing water  discharged  into  a  closet  basin  after 
the  main  flush  from  the  cistern  has  been 
expended.  Its  object  is  to  ensure  that  the 
closet  trap  is  fully  charged. 


Air  Compressor. — When  air  is  required 
at  a  very  moderate  pressure  a  steam  engine 
can  be  made  to  serve  the  purpose  of  a  com- 
pressor, in  which  case  the  air  is  drawn  in 
through  the  "exhaust"  port  and  delivered 
through  the  "  inlet "  ports — the  valve  setting 
being  modified  to  suit  the  circumstances.  For 
any  pressure  over  about  20  Ibs.  per  square 
inch,  the  cylinder,  and  especially  its  ends, 
must  be  water-jacketed  in  order  that  the  heat 
due  to  the  compression  of  the  air  may  be 
carried  off.  Slide  valves  are  unsuitable  in 
this  case,  and  their  place  is  usually  taken  by 
disc  valves  automatically  lifted  from  their  seat- 
ings  by  the  suction  and  discharge  of  the  air, 
like  those  of  a  pump.  The  suction  valves  are 
made  as  light  as  possible  and  of  comparatively 
large  diameter,  and  are  fitted  with  very  light 
springs,  so  that  they  may  open  readily  and 
not  "  wire-draw  "  the  incoming  air,  and  also 
close  with  a  minimum  of  shock.  To  ensure 
a  full  cylinder  and  to  diminish  resistance  the 
valves  are,  in  some  cases,  opened  "  positively  " 
by  means  of  cams  in  the  same  manner  as 
those  of  gas  or  oil  engines.  Equally  important 
is  the  reduction  of  clearance  spaces  to  the 
lowest  practicable  degree,  as  any  compressed 
air  remaining  in  the  cylinder  or  valve  passages, 
after  the  piston  has  completed  its  stroke,  repre- 
sents wasted  work. 


The  chief  source  of  loss  in  an  air  compressor 
is  due  to  the  fact  that  the  heat  is  removed 
after  instead  of  during  compression,  with  the 
result  that  much  of  the  work  has  been  use- 
lessly spent  in  producing  heat  which  is  after- 
wards dissipated.  This  loss  may  be  greatly 
reduced  by  dividing  the  work  into  stages,  in 
which  case  the  air  is  compressed  to  a  certain 
point  in  one  cylinder,  then  cooled  by  passing 
through  pipes  surrounded  by  water  and  after- 
wards further  compressed  in  another  cylinder. 
Two  or  more  stages,  with  intermediate  cool- 
ing, are  adopted  according  to  the  range  of 
pressures. 

Air  may  also  be  compressed  by  the  direct 
action  of  falling  water ;  this  method  is  in  use 
at  several  of  the  large  waterfalls  in  America 
and  Canada.  (See  "  COMPRESSED  AIK.") 

E.  L.  B. 

Air,  Atmospheric,  Purity  of. — Air  is  a 

mixture,  composed  approximately  of  oxygen, 
21  % ;  nitrogen,  78'06  % ;  and  argon,  0'94  % 
by  volume.  Traces  of  hydrogen,  carbon 
dioxide,  ammonia,  and  ozone,  as  well  as  of 
the  rare  elements  krypton,  neon,  coronium, 
and  others,  are  normally  present  in  the 
atmosphere,  with  a  variable  amount  of 
aqueous  vapour  and  dust.  The  most  impor- 
tant impurities  are  as  follows  : — 

MICRO-ORGANISMS  AND  DUST. — These  are  by 
far  the  most  dangerous  impurities  to  be 
dealt  with.  Air  free  from  dust  probably  exists 
only  as  a  laboratory  product.  Dust  is  partly 
organic  and  partly  mineral;  it  includes  particles 
of  soil,  vegetable  matter,  animal  substances, 
micro-organisms,  particles  of  sea  salt,  volcanic 
and  meteoric  dust,  soot  and  other  matters 
discharged  from  chimneys,  pollen  of  grasses 
and  flowers  in  the  country.  According  to 
Aitken,  there  are  300  to  3,000  dust  particles 
in  a  cubic  centimetre  of  country  air,  from 
Argyllshire ;  whereas  that  of  London  contains 
48,000  to  150,000  per  cubic  centimetre. 
Mineral  dust  is  found  in  all  parts  of  the 
atmosphere ;  organic  only  in  the  lower  strata. 
Micro-organisms  are  usually  absent  from  the 
air  at  an  altitude  of  over  6,501)  feet  and  over 


AIR 


ENCYCLOPAEDIA  OF 


AIR 


the  ocean  beyond  120  miles  from  land.  The 
air  of  cities  is  rich  in  micro-organisms.  The 
importance  of  dust  as  an  impurity  lies 
in  its  power  of  disseminating  disease,  and 
its  effect  in  the  production  of  rain  and  fog. 
Without  dust  in  the  air  it  appears  certain 
that  we  could  have  neither  rain  nor  fog, 
as  a  nucleus  is  required  for  each  drop  of 
water. 

CARBON  DIOXIDE  exists  in  normal  air  to  the 
extent  of  about  3  parts  in  10,000,  not  4  parts 
as  is  often  stated.  It  results  from  the  oxida- 
tion of  organic  matter,  as  in  respiration  and 
combustion.  It  has  now  been  shown  to  be 
inert  and  non-poisonous,  and  acts  only  by 
displacing  oxygen.  Its  presence  is,  however, 
used  as  an  indicator  of  pollution  from  other 
causes,  and  6  or  7  parts  per  10,000  is  considered 
the  permissible  limit. 

CARBON  MONOXIDE. — This  is  a  colourless 
and  odourless  gas,  very  poisonous,  and 
having  the  same  density  as  nitrogen.  It 
is  found  usually  as  the  result  of  imperfect 
combustion,  or  a  coal-gas  leakage;  1  part 
in  400  of  air  causes  poisoning,  and  1  %  is 
rapidly  fatal. 

SEWER  GAS. — When  present  in  the  air  in 
large  quantities,  sewer  gas  is  known  to  have 
the  effect  of  lowering  the  power  of  resistance  of 
the  human  system  to  disease,  and  is  moreover 
objected  to  on  account  of  its  characteristically 
unpleasant  smell. 

AQUEOUS  VAPOUR. — This  is  a  very  impor- 
tant constituent  of  the  air,  but  can  hardly  be 
called  an  impurity.  In  the  form  of  fog  in 
smoky  cities  it  is  very  injurious  to  health, 
although  the  evils  arising  from  such  fogs 
depend  on  the  sulphur  acids  and  solid  matter 
held  by  the  water  rather  than  on  the  water 
itself.  When  the  atmosphere  is  very  damp, 
or  approaching  its  saturation  point,  evapora- 
tion is  impeded,  the  effects  of  heat  and 
cold  are  more  felt,  and  depression  and 
other  unpleasant  sensations  are  experienced. 
The  degree  of  saturation  is  called  the 
"relative  humidity,"  it  is  usually  60  to 
75  °/0. 

Other  impurities  may  result  from  special 


trade  processes,  and  under  particular  con- 
ditions, as  in  mines ;  but  the  above  are  those 
of  most  importance  under  ordinary  circum- 
stances in  civilised  countries. 

J.  S.  0. 

Air-Lift. — A    method    of     raising   water, 
petroleum,  &c.,  from  tube  wells,  by  means  of 


RM 


AP 


WT 


RM 


FIG.  1. 


10 


compressed  air.     The  apparatus  is  extremely 
simple    and    usually    consists   of    two   pipes 


AIR 


MUNICIPAL   AND   SANITAEY   ENGINEEEING. 


AIR 


lowered  into  the  borehole — one  for  conveying 
compressed  air,  the  other  for  carrying  the 
water  to  the  surface ;  both  pipes  are  sub- 
merged to  a  certain  depth  in  the  liquid 
o  bj  raised.  Eef erring  to  Fig.  1,  A.  P. 


FIG.  2. 

represents  the  air  pipe,  R.  M.  the  water  pipe 
or  rising  main,  and  W.  T.  the  well  tube.  In 
some  cases  the  air  pipe  is  placed  concentrically 
within  the  rising  main  (Fig.  2).  When  the 
well  tube  is  of  sufficient  depth  and  suitable 
area,  it  may  itself  serve  as  a  rising  main. 
The  working  principle  is  as  follows  : — Air  is 


11 


forced  down  the  pipe  A.  P.  and  allowed  to 
escape,  at  the  bottom,  into  the  water  con- 
tained in  the  rising  main  R.  M.  This  aerates 
and,  therefore,  reduces  the  specific  gravity  of 
the  contents  of  R.  M.,  with  the  result  that 
the  liquid  is  pressed  or  floated  upwards  by 
the  superior  weight  of  the  column  of  non- 
aerated  liquid  outside  it ;  as  this  leads  to  a 
constant  replenishment  of  the  rising  main 
the  liquid  rises  in  a  continuous  stream.  The 
drawings  show  the  form  of  nozzle  used  by 
Dr.  Pohle,  the  reintroducer  of  the  system. 
Since  that  time  various  improvements 
have  been  made  in  details ;  most  of  them 
consist  in  discharging  the  air  through  a 
narrow  slit  in  order  that  it  may  more 
thoroughly  mix  with  the  liquid  and  avoid 
the  formation  of  large  bubbles  which  are 
apt  to  slip  through  the  water  without  doing 
their  share  of  work  and  also  cause  a  pul- 
sating delivery.  A  recent  improvement  is 
to  employ  a  tapered  rising  main  (Price's 
Patent)  which  allow7s  the  air  to  expand  later- 
ally and  permits  the  velocity  of  the  water 
to  be  more  uniform.  The  air  acts  entirely 
by  volume  as  it  has  only  to  impart  buoy- 
ancy to  the  water,  but  in  order  to  escape 
into  the  rising  main  it  must  be  supplied  at 
a  pressure  just  sufficient  to  overcome  that 
due  to  the  column  of  water  above  the  nozzle. 
As  this  pressure  diminishes  as  the  top  of 
the  pipe  is  approached  the  bubbles  of  air 
expand  (isothermally)  as  they  rise  and  escape, 
at  atmospheric  pressure,  at  the  outlet.  If 
the  water,  after  being  raised,  has  to  be  taken 
in  a  lateral  direction  it  should  be  allowed 
to  flow  there  by  gravity  from  an  open  tank, 
into  which  the  rising  main  discharges,  other- 
wise there  will  be  a  difficulty  in  getting  rid 
of  the  air.  The  "  submergence  "  or  depth  that 
the  nozzle  has  to  be  immersed  in  the  water 
contained  in  the  borehole  is  governed  by  the 
height  of  the  lift,  in  other  words,  the  distance 
from  the  working  level  of  the  water  in  the  well, 
to  the  height  to  which  it  is  to  be  raised.  In 
practice  this  varies  from  one  and  one-third 
to  about  twice  the  lift.  Generally  speaking, 
the  deeper  the  submergence  the  greater  is  the 


AIR 


ENCYCLOPAEDIA   OF 


ALG 


economy,  as  less  air  is  wasted  ;  on  the  other 
hand  the  borehole  must  be  correspondingly 
deepened  and  the  air  pressure  increased 
in  proportion.  Although  the  efficiency  is 
low,  seldom  reaching  40  %  under  the  best 
conditions,  its  great  simplicity  and  conveni- 
ence, coupled  with  the  fact  that  more  water 
can  be  raised  by  this  system,  from  a  given 
sized  borehole,  than  by  any  other  means, 
give  it  an  important  place  amongst  water- 
raising  appliances.  The  system  is  in  use  for 
public  water  supply  purposes  at  the  Birken- 
head  and  Tunbridge  Wells  Corporation  Water- 
works. (See  "COMPRESSED  AIR,"  "Am 
COMPRESSORS,"  "  HYDROSTATIC  HEAD.") 

E.  L.  B. 


Air   Vessel. — (See  "  PUMPS  AND  PUMPING 
MACHINERY.") 


Algae,  Growth  in  Water  Supplies.— 

Numerous  low  forms  of  vegetable  life  may 
occur  in  potable  waters,  and  many  of  these 
it  is  impossible  to  classify  or  to  identify. 
During  their  life  history  some  assume  several 
different  forms,  and  frequently  free  swimming 
cells  are  found  which  may  belong  to  the 
animal  kingdom  or  may  simply  be  the  spore 
form  of  an  algae,  or  of  a  fungus.  Practically 
all  the  extremely  small  organisms  which 
contain  chlorophyll  are  algae,  and  Cooke's 
definition  of  these  may  be  accepted  as  most 
useful  for  all  practical  purposes.  "  Algals,  or 
Algae,"  he  says,  are  "  cellular  flowerless 
plants,  for  the  most  part  without  any  proper 
roots,  or  mycelium,  living,  with  rare  excep- 
tions, entirely  in  water,  and  imbibing  nutriment 
by  their  whole  surface,  from  the  medium  in 
which  they  grow."  Just  as  the  colouring 
matter  of  leaves  varies  from  the  darkest  green 
to  the  brightest  red,  so  the  colouring  matter 
in  the  algae  varies,  but  the  great  majority 
contain  chlorophyll  of  some  shade  of  green. 
In  the  absence  of  sunlight  they  cease  to  grow, 
light  being  essential  for  the  formation  of 


chlorophyll.  Warmth  encourages  growth, 
cold  retards  it,  and  probably  there  is  a  range 
of  temperature  for  each  organism  within 
which  it  can  live  but  beyond  which  it  will 
speedily  perish.  There  is  doubtless  also  an 
"  optimum  "  temperature  at  which  growth  is 
most  rapid.  Many  of  these  low  forms  of 
plant  life  produce  spores,  and  these  are  far 
more  resistent  to  adverse  influences  than  the 
organisms  which  produced  them,  hence  after 
all  growth  has  apparently  disappeared  from 
the  water  spores  may  be  lying  dormant, 
capable  of  producing  an  abundant  crop  as 
soon  as  the  environment  is  once  more  favour- 
able. Whilst  many  are  capable  of  growing 
in  the  purest  of  natural  waters,  there  is  no 
doubt  that  rapid  proliferation  is  only  possible 
where  the  water  contains  traces  of  impurity 
in  solution.  In  large  reservoirs  algoid  growths 
rarely  prove  troublesome,  but  occasionally  for 
some  unexplained  reason  some  species  will 
multiply  with  such  enormous  rapidity  as  to 
discolour  the  whole  of  the  water,  and  on 
occasions  impart  to  it  an  odour  and  taste. 
Usually  the  latter  do  not  develop  until  the 
stage  of  rapid  development  is  passed,  then  the 
nutriment  in  the  water  being  exhausted  or  the 
conditions  having  become  unfavourable,  the 
organism  dies,  and  in  decomposing  produces 
the  compounds  which  impart  the  odour  and 
taste.  Apart  from  the  trouble  which  may  be 
caused  by  the  development  of  any  odour,  these 
organisms  when  in  unusual  abundance  rapidly 
choke  sand  filters,  and  cause  grave  incon- 
venience. Often  when  a  water  has  been 
cleared  from  one  class  of  organism  others  will, 
at  a  later  date,  appear.  Thus  in  the  Staines 
reservoir  of  the  Metropolitan  Water  Board  an 
enormous  growth  of  Oscillatoria  appeared  in 
the  autumn  of  1907.  By  the  use  of  copper 
sulphate  these  were  removed,  but  in  the 
spring  of  the  following  year  Atterionetta, 
Synedra  and  Cyclotdla  appeared  and  seriously 
impeded  the  process  of  filtration.  Algae  are 
more  prone  to  appear  in  uncovered  small 
reservoirs,  especially  if  fed  by  spring  water. 
Covering  so  as  to  exclude  light  is  the  only 
effectual  remedy.  For  further  information 


12 


ALL 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


AMB 


on  this  important  subject  consult  Cooke's 
"  Fresh  Water  Algae  "  and  Thresh's  "  Examina- 
tion of  Water  and  Water  Supplies."  Valuable 
information  bearing  upon  the  removal  of  algse 
by  copper  sulphate  will  be  found  in  a  paper 
by  Dr.  Kemna  in  Yol.  XL  of  the  "  Transac- 
tions of  the  Association  of  Water  Engineers." 
(Vide  also  section  on  "  MICRO-ORGANISMS  IN 

WATER.") 

J.  C.  T. 

Alloys. — (See  "  METALS.") 

Alumina  and  Lime  (treatment  of 
sewage). — The  sewage  of  the  eastern  dis- 
trict of  the  city  of  Glasgow  is  treated  with 
the  precipitants  alumina  and  lime  in  the 
proportion  of  two  of  the  former  to  one  of  the 
latter.  The  sludge,  after  the  admixture  of 
hot  lime,  is  pressed  into  cake  by  means 
of  sludge  presses,  and  when  mixed  with 
street-sweepings  and  ashes  is  disposed  of  for 
manurial  purposes.  The  cost  of  the  treat- 
ment per  million  gallons  of  sewage  is  put 
at  £3  8s. 

Alumino-Ferric  (Spence's)  is  a  com 

mercial  sulphate  of  alumina  containing  a 
small  proportion  of  sulphate  of  iron,  used  as 
a  sewage  precipitant  with  the  after  addition 
of  lime.  It  should  be  free  from  much  excess 
of  acid,  as  this  wastes  the  lime.  The  gela- 
tinous alumina  removes  the  suspended  and 
some  of  the  dissolved  organic  matter,  and  the 
iron  removes  sulphide.  After  sedimentation, 
a  clear  and  colourless  liquid  can  generally  be 
run  off,  leaving  a  voluminous  sludge.  (See 
"PRECIPITANTS  FOR  SEWAGE.") 

Ambulances. — Acts  of  Parliament — Site— 
Accommodation  —  Accessories  —  Ambulances  — 
Stretchers — Litters. 

ACTS  OF  PARLIAMENT. — Public  Health  Act, 
1875  ;  Isolation  Hospitals  Act,  1893. 

SITE. — Ambulance  stations  are  generally  in 
conjunction  with  or  near  the  police  or  fire 
station,  the  horses  being  then  available  for 
both  purposes. 


ACCOMMODATION. — Provision  must  be  made 
for  the  housing  of  one  or  more  horse  ambu- 
lance vans,  one  or  more  hand  stretchers, 
attendants'  house,  work  room,  harness  room, 
stables  for  horses  with  store  rooms  and  hay 
loft. 

ACCESSORIES.  —  This  article  deals  more 
particularly  with  the  necessary  appliances 
needed  for  street  ambulance  work  rather  than 
ambulance  stations,  and  these  consist  of 
ambulance  carriages  and  wagons,  stretchers, 
and  litters.  Each  apparatus  will  be  briefly 
dealt  with,  including  the  materials  used  in  its 
construction. 

AMBULANCE  CARRIAGES  AND  WAGONS. — It  is 
a  difficult  matter  to  lay  down  hard  and  fast 
rules  for  the  construction  of  these,  as  many 
points  have  to  be  taken  into  consideration, 
e.g.,  the  amount  available  for  the  supply  of 
horses,  the  nature  of  the  roads,  &c.  The 
horse  ambulance  is  the  one  recommended  by 
the  St.  John's  Ambulance  Association.  "  It 
is  capable  of  carrying  three  patients  on 
stretchers  and  one  attendant  inside.  The 
stretcher  and  its  mountings  on  the  off  side  of 
the  carriage  can  be  removed,  folded  up,  and 
attached  to  the  roof,  the  cushion  which  was 
resting  on  the  brackets  designed  for  the  pur- 
pose being  removed.  The  upper  stretcher  on 
the  near  side  is  mounted  on  an  elevator  which 
can  be  lowered  much  on  the  principle  of 
parallel  rulers.  This  elevator  can  be  removed, 
and,  if  made  to  fold  up,  can,  with  the  stretcher, 
be  attached  to  the  roof.  The  lower  stretcher 
and  its  mountings  are  also  made  detachable, 
and  when  removed,  an  omnibus  remains, 
while,  if  desired,  the  whole  of  the  fittings 
restore  the  vehicle  to  an  ambulance  for  three 
stretcher  cases.  The  dimensions  of  the  body 
of  the  carriage  are:  height,  6  ft.;  width, 
4  ft.  6  in.;  length,  6  ft.  4  in.:  the  well 
extending  approximately  4  ft.  6  in.  from 
the  rear.  A  cupboard  is  available  for  surgical 
appliances  when  the  off  side  stretcher  is  not  in 
position,  but  this  has  to  be  removed  when  this 
stretcher  is  used."  ("  Municipal  Engineer's 
Specification,"  1905,  p.  83.)  The  doors  at 
the  back  of  the  carriage  are  hung  folding  and 


13 


AMB 


AMI 


should  leave  the  whole  of  the  back  clear,  to 
give  easy  access  and  facilities  for  getting  the 
stretchers  in  and  out. 

Ventilation  is  obtained  by  having  some  of 
the  small  lights  on  the  side  made  to  open. 
The  materials  used  in  the  construction  are 
ash  for  the  framework  with  mahogany  panels, 
the  well  being  made  with  birch  sides  and  deal 
floor,  the  roof  of  pine  covered  with  canvas  and 
painted.  Cushions  should  be  stuffed  with  hair 
and  covered  with  leather  or  waterproof  canvas. 
The  "  Municipal  Engineer's  Specification," 
1905,  p.  83,  gives  the  following  different 
varieties  of  horse  ambulances  : 

1.  Van-shaped  without  a  well. 

2.  Van-shaped  similar  to  No.  1  but  provided 
with  a  short  well,  room  being  left  for  the  turn- 
ing of  the  front  wheels  under  that  part  of  the 
body. 

3.  A  similar  vehicle  with  a  long  well,  and  a 
fore-carriage   under   which   the  front  wheels 
turn. 

4.  Brougham  shaped. 

5.  A  light  four-wheeled  conveyance. 
STRETCHERS. — These   consist   of   a   bed  on 

which  the  patient  reclines,  poles  and  tra- 
verse bars  and  also  feet,  carrying  straps,  and 
straps  for  securing  the  patient,  and  a  hood  or 
covering  of  canvas.  A  stretcher  generally 
weighs  from  20  Ibs.  to  30  Ibs. 

BED. — This  is  generally  about  6  ft.  long  and 
22  in.  wide.  The  bed  is  generally  made  of 
canvas,  sail-cloth,  woven  wire,  cane,  or  other 
suitable  materials.  It  is  advisable  not  to  have 
tbe  width  more  than  22  in.,  or  transport  by 
railway  will  be  impossible. 

The  bed  must  be  firmly  fixed  to  the  poles, 
though  easily  capable  of  being  detached 
when  necessary.  Pillows  or  cushions  may  be 
provided. 

POLES. — These  may  be  of  ash  or  pine,  steel 
tubing,  or  wood  and  iron  combined,  and  extend 
about  12  in.  beyond  the  bed  at  each  end. 
The  upper  side  should  be  rounded  to  afford 
protection  for  the  canvas.  The  handles  may 
with  great  advantage  be  telescopic. 

TRAVERSE  BARS. — These  are  used  to  keep  the 
poles  apart  and  complete  the  framework  on 


which  the  bed  is  fixed  and  kept  tight.  They 
are  generally  hinged  to  allow  of  the  stretcher 
being  folded  up  when  not  in  use.  The  material 
is  the  same  as  the  poles. 

FEET. — These  are  generally  of  wood  or  iron 
and  fitted  with  castors,  to  allow  of  the  stretcher 
being  pushed  about.  They  should  raise  it  about 
6  in.  from  the  ground. 

STRAPS. — The  carrying  straps  are  made  of 
either  web  or  leather,  and  have  adjustable 
loops  for  regulating  the  length  for  bearers  of 
different  heights.  The  straps  for  securing  the 
patient  are  of  the  same  material,  and  two  or 
three  in  number,  and  for  police  purposes  wrist 
straps  are  provided. 

LITTERS. — The  following  is  a  specification  of 
litters  by  the  St.  John's  Ambulance  Association 
appearing  in  the  "  Municipal  Engineer's  Speci- 
fication," No.  1,  1905,  p.  83,  and  if  followed 
will  give  all  the  necessary  requirements  for  this 
class  of  ambulance: — "Litters.  The  Ashford 
litter  undercarriage  is  provided  with  two  wheels 
36  in.  in  height,  usually  with  indiarubber  tyres. 
It  has  a  cranked  axle  to  enable  the  stretcher- 
bearers  to  pass  between  the  wheels  instead  of 
lifting  the  stretcher  over  them.  It  is  fitted 
with  four  arms,  capable  of  being  used  as  legs 
or  handles,  which  can  be  locked  in  either  a 
horizontal  or  vertical  position.  A  hood  and 
apron  are  usually  supplied  as  part  of  the 
litter." 

E.  H.  B. 

American  Tube  Wells, — (See  "  ABYS- 
SINIAN WELLS.") 

Amines  Process  (sewage  treatment). 

— This  is  a  chemical  precipitation  process, 
which,  it  is  claimed,  sterilizes  the  sewage.  The 
precipitants  used  are  lime  and  herring-brine, 
in  the  proportion  of  22^  grains  per  gallon  of 
lime  and  4  grains  of  the  brine.  Lime  alone 
in  large  quantities  inhibits  putrefaction  and 
nitrification.  In  1891  the  system  was  tried  at 
Salford,  on  the  continuous  flow  principle.  The 
wet  sludge  amounted  to  about  26  tons  per 
million  gallons. 


14 


ANE 


MUNICIPAL   AND   SANITAKY  ENGINEERING. 


ANT 


Anemometer. — The  direction  of  the  wind 
can  be  ascertained  from  the  indication  of  a 
well-balanced  vane  or  weathercock  ;  or  when 
this  is  not  available  by  observing  the  drift  of 
smoke.  The  velocity  and  pressure  of  the  wind 
are  recorded  by  means  of  anemometers.  The 
instrument  most  generally  used  is  the  Robin- 
son cup  anemometer.  In  this  instrument  four 
hemispherical  cups,  fixed  at  the  extremities  of 
cross  arms  attached  to  a  vertical  axis,  are 
caused  to  rotate  by  the  force  of  the  wind.  By 
means  of  an  endless  screw  the  revolutions  of 
the  vertical  axis  are  communicated  to  a  series 
of  wheels,  which  indicate  on  dials  the  number 
of  miles  of  wind.  The  graduations  have  been 
calculated  on  the  supposition  that  the  velocity 
of  the  wind  is  three  times  that  of  the  motion 
of  revolution  of  the  cups.  Later  experiments, 
however,  have  shown  that  this  value  is  too 
high,  and  differs  also  with  the  size  of  the 
instrument.  For  anemometers  with  9-in. 
cups  and  2-ft.  arms  the  factor  is  2'2,  and  for 
anemometers  with  5-in.  cups  and  1-ft.  arms 
the  factor  is  2*8.  The  difference  between 
consecutive  readings  of  the  dials  gives  the 
number  of  miles  of  wind  which  have  passed 
the  cups  since  the  last  reading.  It  is  cus- 
tomary to  express  the  rate  of  the  travel  of  the 
wind  in  miles  per  hour.  The  instrument  can 
be  constructed  to  give  a  continuous  record  of 
the  velocity  of  the  wind.  (For  other  forms  of 
anemometers,  see  "WIND  FOKCE.") 

W.M. 

Anaerobic  bacteria  (in  sewage  treat- 
ment).— (See  "  AEKOBIC  AND  ANAEKOBIC.") 

Anti  -  Siphonage    Pipes.  —  (See    "  Si- 

PHONAGB.") 

Antiseptics  are  agents  which  retard  or 
prevent  putrefaction  or  decay.  The  difference 
between  them  and  disinfectants  is  mainly  one 
of  purpose  ;  the  latter  being  directed  to  the 
destruction  of  the  organisms  of  disease,  and 
the  former  to  the  prevention  of  injury  by 
microbial  life  to  food  or  other  commercial 


products.  Nearly  all  concentrated  chemical 
solutions  hinder  the  growth  of  organisms,  but 
many  of  them  in  weak  dilution  actually  pro- 
mote the  development ;  instances  are,  salt, 
sugar,  and  acetate  of  potash.  Disinfectants 
require  to  be  antibacterial  in  a  much  weaker 
state.  Another  difference  is  that  antiseptics  as 
used  in  food  must  obviously  be  non-toxic.  Since 
organisms  only  grow  actively  within  certain 
limits  of  temperature  and  require  water  for 
their  development,  heat  and  cold  outside  those 
limits,  or  drying,  act  as  natural  antiseptics. 
Tinned  goods  are  usually  heated  to  boiling 
point  or  a  little  higher,  but  a  temperature  of 
65-70°  C.,  maintained  for  twenty  minutes, 
kills  nearly  all  bacteria  though  not  their 
spores,  and  is  sufficient  to  preserve  milk  for  a 
reasonable  time.1  As  to  the  effect  of  cold,  flesh 
is  preserved  in  commerce  either  as  chilled,  near 
freezing  point,  from  1  to  2°  C.,  or  for  a  longer 
time  as  hard  frozen,  from  9  to  18°  C. ;  butter 
at  temperatures  down  to  15°  C.,  milk  is  frozen 
at  0'5°  C.,  while  fruits  keep  better  just  above 
freezing.  Even  at  10°  C.  bacterial  multipli- 
cation is  checked.  Many  organisms,  how- 
ever, survive  even  when  cooled  to  —  252°  C. 
(Macfadyen  &  Rowland),  therefore  decay  can 
recommence  when  the  temperature  is  raised. 

Chemical  antiseptics  are  numerous,  and  not 
all  innocuous.  Ordinary  "  smoking "  dries 
the  surface  and  also  impregnates  it  with 
acetic  acid,  formaldehyde  and  creosote.  In 
salting  the  antisepsis  is  subordinate  to  a  pro- 
cess of  diffusion  whereby  the  salt,  with  some- 
times nitre  and  sugar — neither  of  them  strong 
antiseptics — pass  inwards  and  displace  the 
juices  containing  putrescible  albuminoids : 
these  pass  out  into  the  brine  and  leave  the 
food  drier  and  less  susceptible  to  change,  but, 
deprived  of  about  one-third  of  its  nutritive 
value,  apt  to  cause  scurvy  when  used  too 
exclusively  as  a  diet,  and  also  less  digestible. 
Small  quantities  of  certain  stronger  anti- 
septics enable  the  original  qualities  to  be  in 
great  part  retained,  and  prevent  decay  for  a 

1  The  International  Congress  of  Hygiene,  1903, 
agreed  on  a  minimum  of  85°  C.  for  "  Pasteurization," 
but  this  had  main  reference  to  tubercle  bacilli. 


15 


ANT; 


ENCYCLOPAEDIA   OF 


ART 


considerable  period  with  less  influence  on 
digestion  than  the  old  curing  processes.  Meat 
has  been  preserved  with  moderate  success  in 
an  atmosphere  of  carbonic  acid.  Joints  are 
often  injected  in  the  cavities  with  preservative 
solutions,  usually  boric  acid,  to  wash  out 
serous  liquid  and  leave  a  small  quantity  of 
the  antiseptic.  Most  acids  are  more  or  less 
inimical  to  bacteria  and  therefore  inhibit 
putrefaction  ;  the  value  of  acetic  acid  for  this 
purpose  is  familiar,  and  formic  acid,  which 
has  about  three  times  the  power,  could  prob- 
ably replace  acetic  in  most  of  its  uses. 
Sulphurous  acid  for  foods  is  not  satisfactory, 
but  is  much  used  for  preventing  decay  in 
casks,  for  finings,  and  by  butchers.  Salicylic 
acid  has  been  frequently  employed  in  fruit 
preparations,  but  is  prohibited  in  many 
countries.  Sodium  benzoate  in  O'l  %  strength 
is  probably  safer.  Fluorine  compounds  in 
about  the  same  proportion  are  sometimes 
used  on  the  Continent  in  brewing.  But  the 
most  popular  antiseptics  are  boric  acid  for 
cream,  butter,  bacon,  fish  and  milk,  and 
formaldehyde,  chiefly  for  the  latter.  The 
writer  has  shown  that  1  in  2,000  of  boric 
acid,  or  1  in  50,000  of  formaldehyde,  is 
capable  of  keeping  milk  sweet  for  twenty-four 
hours  even  in  warm  weather,  and  neither  is 
injurious  in  these  proportions.  Many 
aromatic  bodies  are  antiseptic,  but  are  not 
admissible  in  food  on  account  of  their  taste 
or  other  properties.  Total  prohibition  of 
chemical  preservatives  as  sometimes  advo- 
cated is  illogical  in  view  of  the  fact  that  salt, 
nitre,  and  vinegar,  which  can  all  be  poisonous 
and  are  not  the  most  effective  antiseptics,  are 
used  in  such  quantities  without  question.  An 
English  Departmental  Committee  published 
their  investigation  of  the  subject  in  1901,  and 
recommended  that  formaldehyde  be  prohibited, 
that  no  preservative  whatever  should  be 
allowed  in  milk,  that  the  only  preservative 
lawful  in  cream  be  boric  acid  in  amount  not 
exceeding  0'25  %  and  in  butter  and  margarine 
an  amount  not  exceeding  0'5  % ;  that  as  to 
salicylic  acid  not  more  may  be  used  in  foods 
than  1  grain  per  pint  of  liquid,  or  per  pound  of 


solid,  its  presence  in  all  cases  to  be  declared  ; 
finally  that  in  dietetic  preparations  for  infants 
and  invalids  all  chemical  preservatives  be 
prohibited  (special  supply  for  this  purpose 
is  in  many  cases  practised  at  present).  They 
concluded  that  preserving  agents  were  needed, 
that  the  nature  and  amount  should  be  declared 
on  the  label,  and  that  a  Court  of  Reference 
should  be  appointed  to  prescribe  standards 
and  for  questions  arising ;  but  the  subjects 
are  still  awaiting  legislation. 

Another  important  application  of  antiseptics 
is  to  wood  and  cordage,  in  suppressing  destruc- 
tive fungi  and  insects.  The  simple  tarring 
sufficient  for  cordage  does  not  penetrate  the 
interior  of  wood,  so  that  in  the  latter  case  a 
preservative  liquid  is  made  by  pressure  to 
enter  the  vessels.  Copper  sulphate  (Kyanizing) 
was  the  earliest  agent  used,  and  is  still  found 
effective.  Creosote  oils  are  now  commonly 
employed,  but  have  the  disadvantage  of 
increasing  the  inflammability.  S.  E. 

Aqueducts. — Artificial  water-ways  con- 
structed for  the  conveyance  of  water  through 
long  distances,  mostly  for  purposes  of  public 
supply.  (See  "  WATER  SUPPLY.") 

Artizans'  Dwellings. — The  term  "Arti- 
zans'  dwellings "  is  generally  restricted  to 
dwellings  constructed  for  the  accommodation 
of  the  working  classes  by  a  public  company 
or  association,  or  by  a  local  authority  or  other 
public  body,  or  a  philanthropist,  or  group  of 
philanthropists.  They  form  but  a  small  pro- 
portion of  working  class  dwellings,  for  whereas 
there  were  in  1901  about  eight  million 
inhabited  houses  in  the  United  Kingdom 
occupied  hy  about  nine  million  families,  of 
which  it  may  be  assumed  seven  million  were 
of  the  working  class,  the  total  number  of 
families  accommodated  in  artizans'  dwellings 
coming  within  the  foregoing  definition  is  less 
than  a  quarter  of  a  million.  Until  recently  it 
was  the  common  practice  to  construct  most  of 
these  dwellings  on  the  flat  system  in  blocks, 
but  there  has  latterly  been  a  reversion  to  the 


16 


ART 


MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


ART 


cottage  and  other  types  of  small  houses.     The 
dwellings  erected  are  now  of  five  types  : — 

1.  Common     lodging-houses,    with     either 
bunks  or  cubicles,  and  large  common  rooms. 

2.  Block    dwellings,   four    or    five   storeys 
high. 

3.  Tenement  houses  of  three  storeys. 

4.  Cottage  flats  in  two-storey  self-contained 
dwellings. 

5.  Cottages  of  various  sizes,  self-contained, 
with  gardens. 

Among  the  principal  agencies  for  the  erec- 
tion of  lodging-houses  may  be  included 
Eowton  Houses,  Limited,  a  society  which  has 
built  six  "  hotels  for  working  men,"  providing 
5,162  cubicles,  and  having  in  each  house  a 
dining-room,  reading-room,  and  sundry  work- 
shops and  offices  for  common  use,  at  an 
inclusive  cost  of  £400,000  and  an  inclusive 
rent  of  Id.  per  day  which  has  enabled  a  gross 
profit  of  £15,000  per  annum  to  be  made, 
sufficient  to  pay  over  5  %  on  the  capital. 

The  artizans'  dwellings  societies  or  com- 
panies in  London  have  built  dwellings,  mostly 
in  blocks,  for  125,000  persons,  and  throughout 
the  country  420  co-operative  societies  have 
built  48,000  houses,  mostly  cottages,  at  a  cost 
of  £10,000,000. 

Co-partnership  housing  societies,  which 
are  growing  very  rapidly,  have  for  their  basis 
four  main  principles :  first,  that  the  tenants 
should  hold  shares  in  a  society  which  owns 
the  houses ;  second,  that  they  should  share  in 
all  profits  made  by  the  estate ;  third,  that  land 
should  be  bought  in  bulk  and  developed  with 
open  spaces  and  a  limited  number  of  houses 
per  acre  ;  fourth,  that  the  spirit  of  fellowship 
and  community  should  be  fostered  by  the 
formation  of  societies  of  various  kinds,  and  the 
provision  of  rooms  and  institutions  for 
common  use.  They  have  a  capital  of  over 
£1,000,000  and  have  developed  estates  at 
Birmingham,  Baling,  Hampstead,  Letchworth 
Garden  City,  Sevenoaks,  Manchester  and 
elsewhere. 

Municipalities  have  been  entrusted  with 
important  powers  and  duties  with  respect  to 
the  supervision,  improvement  and  provision 

M.S.E.  17 


of  artizans'  dwellings  by  means  of  no  less 
than  28  Acts  of  Parliament,  of  which  the 
chief  are  : — 

(1)  The  Public  Health  Act,  1875  (sanitary 
clauses),    together    with    the    amending    or 
corresponding  measures,  the   Public   Health 
Acts  (Amendment)  Acts,  1890  and  1907,  the 
Public  Health   (London)  Act,  1891,  and  the 
Public    Health    (Scotland)   Act,    1897  ;    and 
bye-laws  made  under  the   provisions  of   the 
same ; 

(2)  The   Housing   of  the  Working-Classes 
Act,  1890,  with  amending  Acts  of  1893,  1894, 
1896,    1900   and   1903,  which   consolidate   a 
number   of   previous   enactments,  known   as 
Artizans'  Dwellings  Acts  ; 

(3)  The  Small   Dwellings  Acquisition  Act, 
1899; 

(4)  The  Municipal  Corporations  Act,  1882 
(Sect.  Ill),  and  the  Working  Classes'  Dwell- 
ings Act,  1890 ; 

(5)  The  Labourers'  (Ireland)  Acts,  1885  to 
1906; 

(6)  The  Standing  Orders  of  Parliament  for 
Local   Improvement   and   Public   Companies 
Bills. 

So  far  as  the  provision  of  houses  is  con- 
cerned, the  most  important  of  these  are  the 
Housing  of  the  Working  Classes  Acts,  1890- 
1903. 

Part  I.  of  the  Act  of  1890  enables  urban 
authorities  to  condemn,  clear  and  re-plan 
insanitary  areas  and  to  construct  dwellings  to 
re-house  the  working  classes  displaced.  Over 
£8,000,000  has  been  spent  under  this  and 
preceding  Acts  on  clearance  schemes,  at  a  cost 
of  £50  to  £70  for  each  person  displaced,  in 
addition  to  an  outlay,  partly  or  wholly  re- 
munerative, of  £50  to  £70  per  head  for 
dwellings  in  which  to  re-house  the  dispossessed. 
The  principal  schemes  have  been  in  London, 
Glasgow,  Liverpool,  Manchester,  Leeds  and 
Birmingham,  but  there  have  been  schemes  at 
Bath,  Birkenhead,  Bolton,  Bradford,  Brighton, 
Coventry,  Devonport,  Dublin,  Leigh,  Plymouth, 
Prescot,  Portsmouth,  Salford,  Sheffield,  South- 
ampton, Stretford,  Sunderland  and  Wigan. 
Part  II.  of  the  Act  provides  for  (1)  the  closing 


ART 


ENCYCLOPEDIA   OF 


ART 


and  demolition  by  urban  and  rural  local 
authorities  of  houses  unfit  for  human  habita- 
tion; (2)  the  removal  of  buildings  which 
obstruct  light  and  air ;  (3)  the  clearance  and 
reconstruction  of  small  unhealthy  areas.  It  is 
estimated  that  there  are  over  700,000  houses 
which  ought  to  be  dealt  with  by  these  pro- 
visions, but  the  average  number  dealt  with 
annually  under  all  three  heads  is  less  than 
10,000,  and  the  amount  spent  on  schemes  for 
clearing  small  areas  from  1890  to  1907  was 
only  about  £150,000.  Part  III.  as  amended 
by  subsequent  Acts  enables  local  authorities 
to  acquire  land,  borrow  money,  and  purchase, 
or  build  and  let  artizans'  dwellings  furnished 
or  unfurnished  of  any  kind.  It  also  enables 
them  to  lease  land  to  companies  and  private 
individuals  for  the  construction  of  such 
dwellings.  It  was  an  "adoptive"  Act,  but 
the  new  Act  of  1909  makes  it  compulsory 
everywhere.  Land  may  be  compulsorily 
acquired  at  its  "fair  market  value"  which 
in  default  of  agreement  has  to  be  determined 
by  a  single  arbitrator  appointed  by  the  Local 
Government  Board. 

Money  may  be  borrowed  by  local  authorities 
either  in  the  ordinary  way  by  mortgage  or  by 
the  issue  of  stock,  or  it  may  be  obtained  at 
rates  varying  with  the  movements  of  the 
money  market  from  3  to  4  per  cent,  from 
the  Public  Works  Loan  Commissioners.  It 
has  to  be  repaid  within  periods  not  exceeding 
80  years  for  the  land,  and  60  years  for  the 
buildings.  The  total  amount  borrowed  under 
Part  III.  amounts  to  about  £2,750,000  of 
which  over  £2,000,000  is  in  respect  of  pro- 
vincial towns.  Part  III.  has  been  "  adopted  " 
by  the  London  County  Council,  12  metro- 
politan borough  councils,  30  county  boroughs, 
45  town  councils,  50  urban  district  councils, 
and  12  rural  district  councils,  or  a  total  of 
149  councils.  Altogether  the  municipalities 
in  Great  Britain  have  built  about  22,000 
dwellings  with  60,000  rooms.  These  include 
30  model  lodging  houses  in  Glasgow,  London, 
Belfast,  Aberdeen,  Manchester,  Salford, 
Southampton,  Blackburn,  Bury,  Paisley,  and 
Perth,  constructed  at  a  cost  of  from  £40  to 


£60  per  inmate,  or  an  average  of  £65  per 
head  for  building  and  furnishing,  and  let  at 
charges  of  from  4d.  to  Id.  or  an  average  of  Qd. 
per  night  inclusive.  Municipal  block  dwell- 
ings to  the  number  of  12,500  with  over  30,000 
rooms  have  been  constructed  in  London, 
Dublin,  Edinburgh,  Glasgow,  Douglas,  Liver- 
pool, Manchester,  Nottingham  and  Sheffield. 
The  cost  of  building  varies  from  £70  to  £140 
per  room,  but  in  most  cases  is  between  £85 
and  £100  per  room  ;  the  rents  per  room 
average  in  London  (per  room)  3s.  Id.  per 
week,  Scotland  and  the  provinces  2s.  3d.  per 
week.  Most  of  the  dwellings  consist  of  two  or 
three  rooms. 

Municipal  tenement  houses  to  the  number 
of  2,800  with  6,800  rooms  have  been  built  in 
Liverpool,  Manchester,  Sheffield,  Plymouth 
and  Devonport.  The  cost  of  building  averages 
£70  per  room ;  rents  average  Is.  Wd.  per 
room  per  week.  Most  of  the  dwellings  are  of 
two  or  three  rooms. 

Municipal  cottage  flats  to  the  number  of 
about  2,200  with  6,000  rooms  have  been  built 
in  Battersea,  Dublin,  East  Ham,  and  West 
Ham.  The  cost  of  building  varies  from  £40 
to  £80  and  averages  £70  per  room  ;  the  rent 
averages  2s.  3d.  per  room  per  week,  and  the 
dwellings  are  about  evenly  divided  between 
two,  three,  and  four  rooms. 

Municipal  cottages  to  the  number  of  4,500 
with  20,000  rooms  have  been  built  in  75  towns 
and  villages,  among  which  the  most  interesting 
schemes  are  those  at  Sheffield,  Eichmond, 
Merthyr  Tydfil,  Sevenoaks,  Hornsey,  and  the 
cheapest  are  in  Altrincham,  Bangor,  Exeter, 
Guildford,  Neath,  Prescot  and  Stretford.  The 
cost  of  building  has  varied  from  £30  to  £80, 
or  an  average  of  £45  per  room.  About  half 
the  cottages  cost  under  £200  each  and  the 
other  half  over  £200  each.  Rents  vary  from 
4s.  to  8s.  per  week  and  average  about  Is.  Gd. 
per  room  per  week.  Half  the  cottages  are  let 
at  6s.  to  7s.  per  week  and  two-thirds  are  under 
7s.  per  week.  Most  of  the  cottages  contain 
four  or  five  rooms  with  a  scullery. 

In  considering  the  relative  costs  of  the 
various  types  of  artizans'  dwellings  there  are 


18 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


ART 


three  points  to  bear  in  mind  :  (1)  The  cost  of 
site,  which  varies  from  £1  10s.  per  room  for 
cottages  on  the  outskirts  of  towns  to  ,£120  per 
room  for  block  dwellings  in  the  centre  of  large 
cities.  (2)  The  cost  of  development  of  the  site 
by  constructing  the  necessary  roads,  sewers 
and  approaches,  which  varies  from  £4  10s. 
per  cottage,  or  £100  per  acre,  to  £45  per 
cottage,  or  £1,000  per  acre,  according  to  the 
nature  of  the  works  required  by  the  bye-laws 
or  by  the  specifications.  Under  present 
conditions  the  cost  of  development  of  building 
sites  for  cottages  is  generally  between  £200 
and  £500  per  acre  in  urban  districts,  so  that 
it  is  often  a  more  important  consideration  than 
the  cost  of  the  site  itself.  (See  "  TOWN 
PLANNING.")  (3)  Cost  of  building  which 
depends  partly  upon  the  varying  cost  of  labour 
in  different  districts  but  also  upon  the  type 
of  house  constructed.  It  will  be  seen  from 
previous  figures  that  block  dwellings  cost 
twice  as  much  per  room  to  build  as  cottages. 
Much  depends  also  upon  the  plans  and 
specifications. 

In  recent  years  great  efforts  have  been  made 
by  means  of  local  cottage  exhibitions  to 
encourage  improved  methods  of  design  and 
construction  for  working  class  dwellings.  At 
Letchworth  Garden  City  a  cheap  cottage 
exhibition  was  held  in  1905,  when  85  cottages 
were  erected  for  competition,  at  a  supposed 
cost  not  exceeding  £150  per  cottage.  A 
second  exhibition  in  1907  comprised  52 
cottages  as  follows  : — Class  A :  Three  rooms 
and  scullery,  £175  ;  Class  B,  four  rooms  and 
kitchen-scullery,  £200 ;  Class  C,  five  rooms 
and  scullery,  £240. 

Cottage  exhibitions  on  municipal  land  have 
since  been  held  as  follows : — 

Sheffield,  1907.  Forty-two  cottages  in  three 
classes  varying  from  £175  to  £225,  all  of 
which  were  purchased  by  the  Corporation  for 
the  sum  of  £8,391,  and  are  now  let  to 
workmen. 

Newcastle,  1908.  Eighty  cottages  built  under 
the  city  bye-laws  on  municipal  land,  and 
varying  in  cost  from  £195  to  £350  upon  city 
land  leased  at  4d.  per  square  yard  per  annum 


for  land  covered  with  buildings  and  Id.  per 
square  yard  per  annum  for  garden  ground. 

Swansea,  1909,  in  course  of  arrangement. 

In  the  three  last-named  cases  the  planning 
of  the  site  was  a  special  feature  of  the 
exhibition. 

RURAL  HOUSING  in  England  has  hardly 
been  touched  by  local  authorities,  only  54 
cottages  having  been  built,  but  the  famous 
Labourers'  (Ireland)  Acts,  1883  to  1906,  have 
had  the  most  remarkable  results  in  Ireland 
owing,  first,  to  the  power  given  to  working  men 
where  cottages  are  scarce  or  deficient  to  make 
an  official  representation  to  the  rural  district 
council,  which  must  be  acted  upon,  and, 
secondly,  to  cheap  money  and  a  Government 
subsidy.  The  terms  for  loans  have  varied  from 
2f  to  '6^%.  The  amount  borrowed  exceeds 
£3,415,000,-  and  the  number  of  cottages  built 
is  over  20,634,  divided  as  follows :  Ulster, 
1,663;  Munster,  10,617;  Leinster,  8,018; 
Connaught,  336.  They  are  let  at  weekly 
rents  varying  from  9d.  to  Is.  Gd.  per  week, 
and  their  average  cost  has  been  about  £150. 
£47,480  was  received  in  rent  for  the  year 
ending  31st  March,  1906 ;  the  Government 
subsidy  was  £41,610,  and  the  rates  contributed 
£63,000.  These  sums  are  just  sufficient  to 
pay  interest  and  instalments  for  repayment  of 
principal  amounting  to  £151,898.  The  rates 
are  paid  by  the  occupiers.  A  new  Act  passed 
in  1906  provides  for  loans  up  to  £4,250,000 
being  advanced  by  the  Irish  Land  Commission 
repayable  on  the  annuity  system  in  68|  years 
at  3^  °/0,  for  interest  and  repayment  on  prin- 
cipal instead  of  £4  11s.  8d.  as  formerly. 
The  Exchequer  grant  of  £37,000  is  to  be 
divided  among  the  districts  building  or  having 
built  cottages  at  a  pro  rata  amount  per 
cottage.  In  future  it  is  estimated  that  the 
cost  of  Irish  labourers'  municipal  cottages 
will  be  paid  Jlrds.  by  the  Government 
subsidy,  ^frds  by  the  labourer,  and  ^rds. 
by  the  rates. 

The   financial  working   of   artizans'  dwell- 
ings  is   a   matter   of    great    importance,    so 
the    following    figures    derived    from    official 
returns    of    various    local    authorities    have 
19  c  2 


ART 


ENCYCLOPAEDIA  OF 


ART 


special  interest.  The  buildings  included  in 
the  returns  only  represent  those  as  to  which 
complete  particulars  are  available. 


London  County 

Eight  Metro- 

Council Com- 

politan 

pleted  Schemes. 

Boroughs. 

Capital  outlay 

£1,900,000 

£393,192 

Kents  received 

120,000 

28,451 

Bates,    Taxes,    Water  and 

Insurance 

28,000 

5,557 

Repairs  and   Maintenance 

12,500 

3,563 

Superintendence  and  Sun- 

dries 

8,000 

868 

Total  working  expenses   .  . 

48,500 

9,988 

Net  return  on  outlay 

3-75% 

4-66% 

Twenty-two 

Forty-five  Towns 

Towns  Dwell- 

Dwellings Built 

ings  Built  on 

on  Open  Land 

Slum  Areas  or 

under  Part  III. 

in  Central 

Districts. 

Capital  outlay 

£930,450 

£991,246 

Rents  received 

64,631 

42,034 

Rates,      Taxes,     and     In- 

surance 

17,490 

9,046 

Repairs  and   Maintenance 

6,472 

7,898 

Superintendence  and  Sun- 

dries 

2,058 

2,070 

Total  working  expenses  .  . 

26,010 

19,692 

Net  return  on  outlay 

4-14% 

2-25  % 

It  will  be  seen  from  the  foregoing  that  the 
percentages  of  rents  on  capital  outlay  are : 
London  County  Council,  6'8  % ;  metropolitan 
boroughs,  7'2%;  forty-five  Part  III.  schemes, 
6*9%;  twenty-two  re-housing  schemes,  4'2%. 

The  percentages  of  the  rent  that  go  for 
various  expenses  are  as  follows: — Rates,  Taxes 
and  Insurance  :  London  County  Council, 
24%;  metropolitan  boroughs,  20%;  forty- 
five  Part  III.  schemes,  27  % ;  twenty-two  re- 
housing schemes,  22  %.  Repairs  and  main- 
tenance :  London  County  Council,  10*5%; 
metropolitan  boroughs,  12'5  %  ;  forty-five 
Part  III.  schemes,  lO'l  % ;  twenty-two  re- 
housing schemes,  18'7%.  As  the  rate  of 
interest  on  loans  was  in  most  cases  3  to  3£  %, 
the  first  three  groups  appear  to  be  self- 
supporting,  and  the  last  group  (dwellings  on 
central  or  slum  sites  in  provincial  towns), 
shows  a  deficiency  of  1  %  per  annum.  It  has, 
however,  to  be  remembered  that  in  the  case 


of  the  London  County  Council,  as  well  as  some 
of  the  metropolitan  boroughs  and  also  some  of 
the  last  group  of  provincial  towns,  the  site 
has  not  always  been  charged  to  the  capital 
outlay  at  its  full  cost,  but  in  some  cases  at  a 
figure  called  the  "  housing  valuation,"  which 
represents  only  the  value  put  upon  the  sites  for 
housing  purposes,  and  varies  from  £2,000  to 
.£4,000  per  acre.  In  some  cases  it  is  only  one- 
tenth  of  the  actual  cost.  If  the  actual  cost  of 
clearance  of  the  slum  sites  be  added  to  the 
capital  outlay,  the  net  return  on  capital  out- 
lay would  remain  the  same  for  the  forty-five 
Part  III.  schemes,  but  would  be  1  %  less  for 
London  County  Council  schemes,  and  %  %  less 
for  the  twenty-two  provincial  re-housing 
schemes.  The  real  justification  for  outlay  on 
municipal  artizans'  dwellings  is  the  saving  of 
life  and  health  which  follow  improvement 
schemes.  Death  rates  have  fallen  30  %  in  the 
last  seventeen  years  for  London  ;  3'7  per  1,000 
on  Plymouth  Part  I.  areas ;  10  per  1,000  in 
Glasgow  during  forty  years ;  17  per  1,000  for 
the  Trowgate  area  ;  and  35  per  1,000  in  respect 
of  slum  areas  cleared  in  Liverpool.  W.  T. 

Artesian  Well. — An  artesian  well  is  a 
boring  into  the  earth  through  which  water  rises. 
In  some  cases  the  water  overflows  under  con- 
siderable pressure,  at  the  surface  of  the  earth, 
due  to  the  natural  phenomena  of  water  finding 
its  own  level.  The  name  "A  rtesian  "  is  derived 
from  the  belief  that  such  wells  were  first 
employed  in  the  French  province  of  Artois, 
but  they  appear  to  have  been  used  at  a  much 
earlier  date  in  Lombardy,  Asia  Minor,  Persia, 
China,  and  Egypt.  The  principle  of  the 
artesian  well  will  be  at  once  apparent  from 
the  figure,  where  it  is  seen  that  a  permeable, 
layer  A  B  exists  between  two  impermeable 
layers  D  E  and  F  G.  Water  enters  the  porous 
strata  at  its  "  outcrop "  at  A  and  B,  and 
accumulates  in  the  bottom  of  the  basin  until 
it  becomes  fully  saturated.  Upon  boring  a 
well  at  C,  the  water  rises  therein  under  a 
head  G  H,  or  other  pressure  according  to  the 
saturation  level  in  the  porous  strata.  The 
water  which  supplies  artesian  wells  is  some- 


20 


ASP 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


ASP 


times  drawn  from  distances  of  as  much  as 
60  or  70  miles.  A  well  at  Grenelle,  in  the 
vicinity  of  Paris,  is  about  1,800  ft.  deep,  and 
yields  about  a  million  gallons  per  day,  the 
temperature  of  the  water  being  80°  F.  Several 
artesian  wells  have  been  sunk  by  the  writer 
through  about  200  ft.  depth  of  Wadhurst  clay 
and  penetrating  a  further  200  ft.  into  the  Ash- 
down  sands  of  the  Hastings  series  for  public 
water  supply  purposes.  The  artesian  rise  of 
the  water  is  about  100  ft.  These  wells  vary  in 
diameter  from  11^  in.  to  about  16  in.  and  are 
lined  throughout  with  steel  tubes,  the  bottom 
lengths  being  perforated.  The  water  is  raised 
in  one  case  by  an  "  air-lift"  and  in  the  other 


Permeable  layer,  A  B,  between  two  impermeable 
layers,  D  E  and  F  G. 

cases  by  deep- well  pumps.  Large  quantities  of 
water  are  obtained  in  a  very  similar  manner 
in  the  Colonies  for  agricultural  and  other 
purposes.  In  Queensland  some  200  million 
gallons  daily  is  obtained  from  borings,  the 
water  in  many  cases  overflowing  at  the  surface 
under  considerable  pressure  necessitating  con- 
trol by  regulating  valves.  Artesian  water  is 
also  largely  used  in  New  South  "Wales,  and  in 
the  Cape  of  Good  Hope,  in  the  United  States, 
Algeria  and  Sahara  and  other  parts ;  its 
discovery  in  all  quarters  proving  an  invaluable 
and  indispensable  aid  to  the  development  of 
the  respective  countries.  It  should  be  re- 
membered that  water  occurring  in  the  chalk 
and  other  strata  is  almost  entirely  contained 
in  the  fissures  of  the  rock,  and  that  borings 
sunk  in  districts  where  such  fissures  are  few 
and  far  between  are  not  likely  to  yield  a  good 
supply.  W.  H.  M. 

Asphalte. — A  native  mixture  of  hydro- 
carbons, found  under  varying  conditions  and 
differing  widely  in  composition.  Its  chief 


use  is  as  an  ingredient  in  numerous  paving 
materials  (patent  and  otherwise);  also,  in 
combination  with  felt,  wire  meshing,  and 
crushed  stone  (lime-stone,  sand,  or  granite), 
for  producing  waterproof  sheeting  for  damp 
courses  (q.  v.),  in  puddling  sheets  as  a  pro- 
tection for  underground  tanks  and  ponds,  and 
for  providing  a  dry  base  for  the  footings  of 
foundations  laid  in  water-logged  soil  or  ground 
traversed  by  freshets ;  also  as  a  damp  exclud- 
ing insulating  material  in  electrical  engineer- 
ing. For  practical  purposes  asphalte  falls 
into  four  broad  groups:  (1)  A  bituminous  mass 
mixed  with  clay  or  niarle,  as  in  the  deposits 
of  Trinidad,  Cuba,  and  Mexico ;  (2)  bitumen 
mixed  with  quartz,  as  in  the  deposits  of  Pyri- 
ment-Seyssel,  Clermont,  &c.  ;  (3)  bitumen 
mixed  with  schist  debris,  as  in  the  deposits 
of  Autun,  Allier,  Dauphine,  &c. ;  (4)  bitumen 
mixed  with  calcareous  debris,  as  in  the 
asphaltes  of  Seyssel,  Val  de  Travers,  Lobsann, 
Clermont,  &c.  The  character  and  behaviour 
of  the  mass  depend  largely  on  the  nature  of 
the  oily  constituents.  Oils  of  the  coal  tar 
group  are  highly  volatile  ;  on  distillation  they 
appear  quite  limpid,  but  quickly  discolour, 
diminish  in  bulk,  and  become  viscous  and 
hard.  Consequently  asphaltes  containing 
coal  tar  oils  soon  become  excessively  brittle, 
dry,  and  rapidly  deteriorate  under  ordinary 
wear  and  even  under  atmospheric  influences. 
For  this  reason  the  many  attempts  to  produce 
artificial  asphaltes  by  mixing  coal  tar  with  lime- 
stone have  failed.  For  paving  purposes  it  is 
necessary  that  the  oil  should  be  non-volatile, 
and  an  evaporative  test  is  usually  demanded. 
But  this  is  of  less  importance  when  the 
asphalte  is  intended  as  a  binder  in  preparing 
solid  dustless  macadam  roads ;  and,  therefore, 
for  this  latter  purpose  artificially  prepared 
asphaltes  (mixtures  of  petroleum  and  car- 
bonate of  lime)  are  admissible.  A  proposed 
specification  for  a  macadam  binder  of  80  per 
cent,  asphalte  contents,  is  as  follows :  (1)  It 
shall  be  soluble  in  bisulphide  of  carbon  to  not 
less  than  99'5  per  cent. ;  (2)  it  shall  be  soluble 
in  carbon  tetrachloride  to  not  less  than  99'5 
per  cent.,  as  a  proof  that  the  mixture  has  not 


21 


ASP 


ENCYCLOPAEDIA   OF 


BAC 


been  overheated,  as  this  would  produce  car- 
benes ;  (3)  when  heated  to  a  temperature  not 
exceeding  500°  F.  until  20  per  cent,  of  the  mass 
is  evaporated,  the  residuum  shall  have  a  pene- 
tration of  not  more  than  10  mm.  when  tested 
with  a  No.  2  needle,  weighted  with  100  grs. 
at  77°  F.,  on  the  Dow  machine  ;  (4)  the  com- 
pound shall  be  sufficiently  liquid  at  working 
temperature  50  cubic  c.m.,  not  to  take  more 
than  200  seconds  to  flow  out  when  tested  in 
an  Engler  viscosimeter  at  212°  F. ;  (5)  the 
solid  contents  of  the  material  shall  consist 
only  of  asphalte,  and  the  consistency  of  the 
residue  shall  not  be  due  to  any  other  solid 
substance,  such  as  paraffin.  The  paraffin 
scale  of  the  total  compound  shall  not  exceed 
1  per  cent.  The  paraffin  scale  is  to  be  deter- 
mined by  destructive  distillation  of  the  entire 
compound  to  coke,  and  determination  of  the 
paraffin  scale  in  the  distillate  ;  (6)  the 
asphalte  binder  shall  not  contain  any  dirt  or 
water,  but  shall  consist  of  pure  bitumen  only. 
Tar  or  substances  recovered  from  acid  sludge 
shall  not  be  admitted.  For  a  binding  material, 
the  above  is  a  rather  drastic  specification. 

For  paving  purposes  asphalte  is  placed  on 
the  market  in  three  principal  forms:  (1)  Partly 
purified,  made  up  into  flat  circular  slabs,  this 
is  melted  in  cauldrons  with  a  small  percentage 
of  bitumen  to  act  as  a  flux,  sand  or  gravel 
usually  being  added,  the  mass  being  poured 
out  on  the  site  to  be  paved,  rolled  out  and  com- 
pressed ;  (2)  in  the  form  of  powder ;  (3)  rock 
asphalte — this  latter  has  to  be  ground  cold  in 
a  special  mill.  Both  these  forms  are  heated  in 
cauldrons  before  use,  laid  while  hot,  pounded 
and  smoothed  with  heated  irons;  (4)  patent 
mixtures,  usually  in  the  form  of  slabs,  to  be 
melted  down  for  laying  in  situ,  and  containing 
special  ingredients,  such  as  cork  refuse,  &c. 

In  electrical  engineering  asphalte  is  used 
in  a  refined  state  (bitumen)  for  insulating  joint 
boxes,  lining  trenches,  and  impregnating  the 
fibrous  outer  casing  of  cables.  (See  "DusT 
PKBVENTION,"  "FOOTPATHS,"  " ROADS,"  and 
"  STREETS.") 

Asphalte  Paving. — (See  "  ROADS.") 


Bacteria. — Classification  and  Morphology. — 
Reproduction. — Products  of  Bacterial  Growth. — 
Influences  affecting  Bacteria. — Observation  and 
Staining. — Culture. — Pathogenic  Bacteria  and 
their  relation  to  Sanitary  Problems. — Diseases 
due  to  other  Micro-organisms. 

CLASSIFICATION  AND  MORPHOLOGY. — Bacteria 
are  minute  unicellular  plants  devoid  of 
chlorophyll.  Bacteriology  comprises  not  only 
the  study  of  bacteria,  but  also  of  other 
micro-organisms,  some  of  which  belong  to  the 
animal  kingdom.  The  micro-millimetre  (M), 
the  thousandth  part  of  a  millimetre,  is  the 
unit  by  which  bacteria  are  measured.  Bacteria 
vary  in  size  from  0'3/x  to  5 'Opt ;  they  are 
classified  according  to  their  shapes :  a  bacillus 
is  rod-like,  a  coccus  is  round  or  spherical, 
while  those  spiral  in  form  are  known  as 
spirilla.  Some  spirilla  may  occur  in  a  shorter 
form  as  curved  rods,  known  as  "  vibriones." 
The  cocci  are  found  grouped  in  characteristic 
ways.  They  may  occur  in  pairs  (diplococci), 
in  chains  (streptococci),  in  clusters  like  a 
bunch  of  grapes  (staphylococci),  and  some 
bacteriologists  add  a  fourth  group  of  cocci 
—  the  sarcinse,  which  divide  in  three 
directions  and  in  two  planes.  Bacteria  are 
not  capable  of  spontaneous  generation ; 
they  can  only  be  produced  from  similar 
organisms. 

REPRODUCTION.  —  Bacteria  reproduce  by 
fission,  the  mother  cell  dividing  into  two 
organisms.  Some  species  are  also  capable 
of  reproduction  by  spores,  which  are  highly 
refractile  bodies,  formed  either  within  the  cell, 
or,  in  some  cases,  the  entire  organism  becomes 
converted  into  a  spore.  Spores  possess  a  re- 
markable resistance  to  physical  and  chemical 
agents.  Few  of  the  pathogenic  bacteria  produce 
spores,  but  B.  antkracis,  B.  tetani,  B.  Welchii 
and  B.  botulinus  are  sporulating  organisms. 
Organisms  deriving  nourishment  from  living 
tissues  are  termed  parasites  in  contradistinc- 
tion to  saprophytes  which  favour  dead  material . 
Most  parasites  can  be  cultivated  on  artificial 
media — the  leprosy  bacillus  being  a  notable 
exception.  While  some  organisms  require 
free  oxygen  (aerobes),  others  exist  only  in  its 


22 


BAG 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BAG 


absence  (anaerobes),  and  some  are  capable  of 
living  under  either  condition. 

PRODUCTS  OF  BACTERIAL  GROWTH.  —  The 
action  of  bacteria  is  generally  of  an  analytic 
nature,  the  complex  material  in  the  media 
being  converted  into  simpler  compounds. 
Surface  soil  contains  large  numbers  of  aerobic 
bacteria  which  diminish  with  depth,  few  being 
found  below  five  feet.  Even  anaerobic  bac- 
teria are  absent  in  the  lower  layers.  When 
brought  in  contact  with  the  soil  bacteria,  the 
proteins,  &c.,  of  cadavers  and  excreta  are 
first  converted  into  liquid  peptone-like  bodies 
by  organisms  of  the  proteus  group.  A  further 
simplification  into  organic  acids  and  simpler 
nitrogenous  bodies  having  occurred,  these 
are  converted  into  ammonium  salts  by  B. 
mycoides,  &c.  The  nitrous  bacteria  convert 
the  ammonium  salts  into  nitrites  (nitrosa- 
tion),  while  the  nitric  organisms  oxidise 
the  nitrites  into  nitrates  (nitratation)  which 
are  available  for  plant  assimilation.  Legu- 
minous plants  have  nodules  on  their  roots, 
which  contain  bacteria  capable  of  absorb- 
ing atmospheric  nitrogen.  Some  soil  bacteria 
have  the  same  property.  Preparations  of 
such  bacteria  have  a  remarkable  effect  on 
poor  soils.  Ptomines  are  produced  in  flesh 
foods  through  bacterial  metabolism.  The 
smell  accompanying  putrefaction  is  due  to 
gases  such  as  methyl  mercaptan,  which  can 
be  detected  by  the  nose  when  ^^.u^o.uuu  °'  a 
milligramme  is  present  in  a  litre  of  air.  The 
symptoms  produced  by  pathogenic  bacteria 
are  mostly  due  to  the  production  of  poisons 
(toxins).  If  the  amount  of  toxin  be  insuffi- 
cient to  cause  death  an  antitoxin  will  in  many 
cases  be  developed  in  the  blood  capable  of 
neutralising  the  toxin.  The  resistance  of  the 
blood  can  be  raised  by  gradually  increasing 
the  dose  of  toxin  until  complete  immunity  is 
conferred  and  the  blood  serum  of  an  immune 
animal  confers  the  protection  on  an  animal 
injected  with  it.  Many  bacteria  produce  gas, 
others  form  a  pigment.  The  characteristic 
red  colour  of  B.  prodigiosus  is  utilised  to 
ascertain  the  identity  of  watercourses  run- 
ning underground  for  a  distance,  and  is  also 


sowed  on  the  surface  soil  to  see  whether  any 
bacteria  can  gain  access  to  a  well  by  percola- 
tion. Yeasts  and  some  bacteria  ferment  the 
carbohydrates.  In  common  with  certain  true 
bacteria,  yeast  cells  contain  unorganised 
ferments  (enzymes)  which  act  after  extraction 
from  the  living  organism.  Bacteria  produce 
the  phosphorescence  on  mackerel  and  decay- 
ing wood. 

INFLUENCES  AFFECTING  BACTERIA.  —  The 
violet  and  ultra-violet  rays  of  the  spectrum 
have  a  germicidal  effect,  the  red  rays  having 
none.  The  electric  arc  has  a  similar  action 
to  sunlight  but  in  a  less  degree.  It  is 
doubtful  if  sunlight  assists  to  any  extent  in  the 
purification  of  water ;  probably  only  organisms 
near  the  surface  are  affected  to  any  degree. 
Bacteria  vary  in  resistance  to  desiccation,  the 
spores  being  especially  resistant.  Cold,  while 
the  exposure  lasts,  inhibits  growth  but  does 
not  kill  bacteria.  The  glass  apparatus  used 
in  bacteriology  is  sterilised  by  exposure  to  dry 
heat  at  150°  C.  for  at  least  half  an  hour. 
Tubes  and  flasks  containing  media  are 
sterilised  under  pressure  in  an  autoclave  or 
on  three  successive  days  in  a  steam  steriliser 
by  an  exposure  on  each  occasion  of  twenty 
minutes  to  one  hour.  This  "Fractional  Steri- 
lisation "  is  calculated  to  allow  spores,  left 
alive  after  the  first  sterilisation,  to  develop 
into  the  more  easily  killed  bacteria.  (See 
also  "DISINFECTANTS,"  and  "DISINFECTION.") 

OBSERVATION  AND  STAINING. — Bacteria  can 
be  examined  with  a  T^th  in.  objective, 
although  for  the  larger  bacilli  in  the  fresh 
condition  a  ^th  in.  is  sufficient.  A  drop  of 
liquid  containing  them  is  placed  on  a  sterile 
microscope  slide  by  means  of  an  inoculating 
needle,1  a  clean  coverslip  is  superimposed  and 
the  microscope  focussed,  using  cedar  wood  oil  if 
the  objective  be  an  "oil  immersion."  Under  the 
microscope  bacteria  appear  as  pale  translucent 

1  An  inoculating  needle  is  a  piece  of  platinum  wire 
fused  into  a  glass  rod.  For  liquids  the  free  end  of  the 
wire  is  bent  into  a  loop  two  or  three  millimetres  in 
diameter.  Before  and  after  use  this  needle  and  such 
part  of  the  rod  as  may  have  become  contaminated  is 
sterilised  by  heating  in  a  Bunsen  flame. 


28 


BAG 


BAG 


bodies,  some  being  capable  of  motion. 
Apparently  they  contain  no  nucleus.  Some 
bacilli  and  spirilla  have  whip-like  threads  of 
protoplasm  (flagella)  which  render  them 
motile.  Bacteria  are  readily  stained  with 
anilin  dyes,  anilin,  phenol,  &c.,  being  used 
as  mordants.  A  droplet  of  water  is  placed  on 
a  clean  coverglass,  and  by  means  of  an  inocu- 
lating needle  some  of  the  material  to  be 
examined  is  added,  mixed  with  the  water, 
spread  evenly  over  the  coverglass  and  allowed 
to  dry.  The  preparation  is  "fixed"  by 
passing  the  coverglass,  held  by  forceps,  three 
times  through  the  Bunsen  flame  at  the  rate 
of  the  swing  of  an  ordinary  clock  pendulum. 
A  solution  of  a  stain  is  added  and  allowed  to 
act  for  a  suitable  time,  when  it  is  drained  off 
and  the  coverglass  washed  in  water  to  remove 
superfluous  stain  when  it  is  again  allowed  to 
dry.  A  drop  of  a  mixture  of  Canada  balsam 
and  xylol  is  placed  on  a  microscope  slide  and 
the  cover-glass  gently  pressed  thereon — pre- 
pared side  downwards — and  examined  with  an 
oil  immersion  lens. 

CULTURE. — The  cultivation  of  bacteria  on 
artificial  media  serves  two  main  purposes  :  it 
allows  the  separation  of  various  organisms  (in 
practice  a  pure  culture  of  a  single  organism 
is  rarely  encountered)  and  "the  manner  of 
growth  on  different  media  is  invaluable  for 
the  identification  of  the  organisms.  A  medium 
constantly  used  is  a  nutrient  broth,  made 
from  extract  of  meat,  peptone,  and  salt.  This 
is  too  acid  and  is  made  neutral  to  phenol- 
phthalein,  and  then  10  cubic  centimetres  of 
normal  hydrochloric  acid  are  added  to  each 
litre  of  the  neutral  broth  (a  reaction  of  +  10 
on  Eyre's  scale).  This  reaction  is  acid  to 
phenol-phthalein  but  alkaline  to  litmus — a 
suitable  reaction  for  most  organisms.  (See 
also  "  BACTERIOLOGY  OF  WATER  "  and  "  BACTE- 
RIOLOGICAL EXAMINATION  OF  DISINFECTANTS.") 
Milk  and  many  other  liquids  are  also  used. 
The  solid  media  are  also  very  numerous  - 
solidified  blood  serum  and  ascitic  fluid, 
potato  and  various  jellies  are  used;  two 
of  these  jellies  are  made  by  adding  to  the 
nutrient  broth,  above  described,  either 


10  per  cent,  of  gelatine  or  1£  per  cent,  of 
agar.  The  former  is  used  for  temperatures 
about  22°  C.,  and  the  latter  for  blood-heat 
cultures.  Gelatine  and  agar  media  are  used 
for  the  isolation  of  various  organisms  — 
some  of  the  material  to  be  examined  being 
mixed  with  the  liquefied  media,  which,  after 
being  poured  into  covered  glass  dishes  (Petri 
dishes),  is  allowed  to  set.  The  individual 
bacilli  are  now  isolated  and  on  incubation 
each  produces  a  colony  of  its  own  species 
which  can  be  submitted  to  examination  and 
sub-cultured. 

THE  EELATION  OF  PATHOGENIC  BACTERIA  TO 
SANITARY  PROBLEMS.  —  The  fans  et  oriyo  of 
sanitary  science  is  the  prevention  of  the 
spread  of  pathogenic  bacteria,  and  although 
this  idea  may  be  wrapped  up  in  a  mass  of 
engineering  problems,  the  principle  is  still 
fundamental.  It  is  therefore  necessary  to 
appreciate  the  various  ways  in  which  infection 
can  be  carried  and  the  means  at  our  disposal 
for  preventing  or  limiting  the  same.  Bacteria 
\vere  at  one  time  considered  to  be  chiefly 
air-borne,  but  with  the  probable  exception  of 
small-pox,  it  is  seldom  that  infection  is  so 
transmitted.  Bacteria  certainly  occur  in  the 
air,  being  carried  on  fine  particles  of  dust ; 
but  even  in  sporadic  outbreaks  of  disease 
other  channels  of  infection  can  usually  be 
identified.  The  presence  of  damp  surfaces  in 
preventing  the  rise  of  "dust  rafts  "  of  bacteria, 
conduces  to  the  reduction  of  the  air  bacteria. 
The  emanations  of  sewers  have  been  con- 
sidered a  predisposing  cause  of  typhoid, 
diphtheria,  and  tonsilitis.  Andrews  and  Hor- 
rocks  have  proved  that  sewer  gas  contains 
sewage  bacteria  and  thus  may  not  only  lower 
the  resistance  of  the  body  to  disease,  but  may 
also  convey  the  specific  bacteria.  Bacterial 
sewage  systems  depend  on  the  solvent  and 
liquefying  action  of  the  sewage  bacteria  on 
the  solids  (see  "  SEWAGE  DISPOSAL  " ).  In 
the  filtration  of  water  through  sand,  an  un- 
satisfactory filtrate  is  obtained  until  a  slimy 
deposit  of  bacteria  and  algae  has  formed  on 
the  filter  bed,  when  a  reduction  of  99  per 
cent,  of  the  organisms  can  be  attained. 


24 


BAC 


MUNICIPAL   AND   SANITAEY   ENGINEERING. 


BAC 


The  typhoid  bacillus  (B.  typlwsus}  occurs  in 
the  eruption,  sweat,  sputum,  urine  and  stools 
of  enteric  patients.  The  urine  and  faeces  by 
gaining  access  to  a  water  supply  may  cause 
infection.  The  typhoid  bacillus  gradually 
dies  out  when  introduced  into  water,  but  it 
appears  from  recent  experiments  by  Houston 
that  although  99'9  per  cent,  of  the  typhoid 
bacilli  disappeared  within  the  first  week,  a 
period  of  nine  weeks  was  necessary  for  its  total 
disappearance.  Hence  the  desirability  of 
storing  water  obtained  from  sources  not  above 
suspicion.  The  typhoid  bacillus  will  live 
longer  in  sterilised  than  in  un sterilised  water 
and  when  inoculated  into  unsterilised  water, 
containing  little  organic  matter,  survives 
longer  than  when  the  organic  matter  is  con- 
siderable. Flies  feeding  on  the  dejecta  of 
typhoid  patients  take  up  the  organism  and 
thus  spread  the  disease.  Shell-fish  and  water- 
cress obtained  from  polluted  waters  are  prone 
to  infection.  The  typhoid  bacillus  may 
remain  latent  in  the  body  for  many  years 
without  its  presence  being  suspected  and 
without  the  host  giving  any  indications  of 
the  disease.  The  "  typhoid  carrier  "  through 
the  discharge  of  infected  faeces  may  thus  un- 
wittingly cause  serious  outbreaks  of  the 
disease.  Apparently  about  3  to  4  per  cent, 
of  typhoid  convalescents  become  chronic 
"  carriers "  while  still  more  are  temporary 
"carriers"  for  2  or  3  months.  Although 
soil  in  this  country  may  become  polluted  with 
typhoid,  its  capability  of  conveying  the  dis- 
ease is  more  restricted  than  in  hot  countries. 
In  India  excreta  are  buried  in  the  ground, 
and  during  the  frequent  dust  storms  are 
carried  with  the  dust  for  long  distances. 
Virgin  sandy  soil  and  peat  are  inimical  to  the 
growth  of  the  typhoid  bacillus  and  it  lives 
longer  in  moist  soils  than  in  dry.  It  rapidly 
dies  in  a  cultivated  soil,  owing  to  the  antago- 
nistic action  of  the  other  bacteria.  Typhoid  can 
be  conveyed  by  fabrics,  soiled  blankets,  &c., 
producing  cases  through  subsequent  use.  It 
is  generally  agreed  that  the  clinical  pheno- 
mena, known  as  "  typhoid  fever "  are  not 
necessarily  due  to  the  B.  typhosus,  other 


organisms  of  the  typhoid-coli  group  pro- 
ducing it.  The  group  of  organisms  classed 
as  "dysentery  bacilli  "  are  found  in  the  stools 
of  epidemic  dysentery  and  infantile  summer 
diarrhoea.  There  is  no  record  of  them  being 
found  in  water. 

B.  coli  communis  is  a  normal  inhabitant  of 
the  colon  of  man  and  the  lower  animals.  It 
has  also  been  found  in  the  intestines  of  carrion 
birds  and  of  some  fish.  Apart  from  its  pyogenic 
and  other  pathological  qualities,  it  is  of  interest 
as  an  indicator  of  faecal  contamination  of  water, 
milk,  shell-fish,  &c.  While  in  some  respects 
resembling  the  typhoid  bacillus,  it  shows 
certain  marked  morphological  and  cultural 
differences.  It  has  three  or  four  flagella  and 
is  feebly  motile,  B.  typlwsus  being  actively 
motile  and  possessing  eight  to  twelve, 
flagella. 

The  Spirillum  cholera  Asiaticce,  or  the 
"  Comma  Bacillus,"  is  the  specific  organism 
of  cholera.  (Chicken  cholera  and  hog  cholera 
are  due  to  totally  different  organisms.)  It  is 
found  in  the  "  rice  water  "  stools  and  vomit  of 
cholera  patients,  and  may  be  conveyed  by 
water,  milk,  uncooked  vegetables,  flies  and 
fomites.  Cholera  spreads  most  rapidly  when 
the  earth  temperature  is  high  ;  this  is  generally 
coincident  with  low  ground  water.  Pettenkofer 
observes  that  an  increase  in  cholera  is  often 
preceded  by  a  fall  in  the  ground  water.  In 
water,  the  cholera  spirillum  rapidly  dies  out, 
but  while  present  is  most  likely  to  be  found 
on  the  surface. 

J5.  anthracis,  the  organism  of  "  wool  sorters' 
disease "  and  "  malignant  pustule,"  forms 
highly  resistant  spores.  It  has  been  found  in 
a  catch-pit  in  a  hide  factory,  in  sewage  and 
tannery  effluents,  in  Yeo  mud,  and  in  feeding 
stuffs.  It  chiefly  enters  this  country  on 
Persian  wool,  Chinese  hides,  and  Russian 
hair,  the  blood  stains  and  not  the  dust  being 
probably  the  actual  carriers  of  the  germs. 
The  spores  in  the  bloody  discharges  not  only 
make  anthrax  endemic  in  the  vicinity  but  are 
probably  also  distributed  by  wind  and  flood. 
Earthworms  have  been  said  to  carry  the 
spores  from  buried  carcases  to  the  surface, 


25 


BAG 


ENCYCLOPEDIA   OF 


BAG 


but  this  is  questioned.  "  Eag  sorters'  "  disease 
is  due  to  another  bacillus.  (Shoddy  is  prepared 
by  the  disintegration  of  disused  garments  and 
other  cloth  likely  to  be  contaminated  with 
bacteria,  which  are  mixed  with  some  new  wool 
and  freshly  woven.  Such  disused  garments 
are  also  made  into  "  flock  "  for  stuffing  mat- 
tresses. As  the  old  material  is  very  seldom  dis- 
infected in  any  way,  and  is  of  a  nature  that 
favours  the  retention  of  bacteria,  its  use  is 
attended  with  danger,  and  legislation  on  this 
point  is  strongly  needed.) 

B.  tuberculosis  may  affect  the  lungs,  peri- 
toneum, the  membranes  surrounding  the 
brain,  the  skin,  bones,  and  lymphatic  glands, 
producing  the  various  manifestations  of  tuber- 
culosis. Like  the  leprosy  and  smegma  bacilli, 
it  is  "  acid-fast,"  i.e.,  when  stained  with  hot 
carbol-fuchsin,  the  colour  is  not  easily  removed 
by  25%  sulphuric  acid.  Certain  bacteria 
occurring  in  butter  and  fodder  have  the  same 
property,  and  hence  the  presence  of  an  acid- 
fast  organism  in  milk  or  butter  offers  only 
presumptive  evidence  of  tubercle.  The  cow 
suffers  from  tuberculosis,  which,  when  affect- 
ing the  udder,  infects  the  milk.  The  bovine 
tubercle  bacillus  is  generally  supposed  to  be 
identical  with  the  human  bacillus,  and  when 
present  in  milk  is  held  responsible  for  abdo- 
minal tuberculosis.  The  flesh  may  also 
contain  this  organism,  and  the  cooking  is 
often  insufficient  to  destroy  it.  Birds  also 
suffer  from  the  disease,  and  although  the 
avian  bacillus  possesses  slightly  different 
characters,  organisms  with  the  characters  of 
the  avian  bacilli  have  been  isolated  from  the 
human  subject.  The  tubercle  bacillus  abounds 
in  phthisical  sputum,  and  it  is  by  inhalation 
of  either  dried  expectoration  or  the  wet  spray 
expelled  when  a  patient  coughs,  that  the 
disease  is  chiefly  conveyed.  It  is  also  conveyed 
by  flies,  and  on  the  bodies,  particularly  the 
lips  and  hands,  of  patients.  The  dust  in 
railway  carriages,  public-houses,  and  the 
homes  of  patients,  is  often  the  cause  of  infec- 
tion. Operatives  in  trades  in  which  particles 
of  dust  are  produced,  are  very  liable  to  the 
disease.  The  compulsory  segregation  of 


infected  persons  being  impossible,  recourse 
must  be  had  to  the  prohibition  of  promiscuous 
expectoration,  a  judicious  use  of  disinfectants, 
and  proscription  of  infected  food  to  reduce  the 
disease;  while  the  resistance  of  the  body  is 
materially  increased  by  improved  ventilation 
and  general  sanitary  conditions,  prevention  of 
overcrowding,  better  feeding,  and  alleviation 
of  social  misery. 

B.  diphtheria  occurs  in  the  throats  of  per- 
sons suffering  from  diphtheria,  and  forms 
toxins  which  are  carried  by  the  circulatory 
system.  It  is  also  occasionally  found  in 
throats  of  healthy  persons.  The  disease  is 
more  prevalent  in  temperate  than  in  tropical 
climates  and  is  conveyed  chiefly  by  personal 
contact,  although  epidemics  have  been  traced 
to  milk,  while  it  is  possible  that  the  bacteria 
are  also  carried  by  the  dust  and  wind.  Sewer 
emanations  predispose  to  the  disease.  An 
organism  simulating  the  true  diphtheria 
bacillus  is  sometimes  met  with  (Hoffman's 
bacillus). 

Streptococci  occur  in  puerperal  fever,  scarlet 
fever,  sore  throat,  meningitis,  &c.  Diplococci 
occur  in  pneumonia  and  gonorrhoea.  These 
strepococci  and  diplococci  are  pyogenic,  as 
also  are  the  staphylococci  found  in  a  variety 
of  affections. 

Tetanus  is  caused  by  the  introduction  into 
a  wound  of  the  B.  tetani,  which  occurs  in  soil 
and  manure.  It  forms  spores  which,  when 
stained,  give  the  appearance  of  drumsticks. 
Influenza  is  due  to  a  bacillus.  It  may  per- 
haps affect  dogs  and  cats,  and  "  pink  eye  "  in 
horses  is  probably  due  to  the  same  bacillus. 
B.  mallei  produces  glanders  and  farcy,  and 
chiefly  affects  horses,  asses,  and  mules. 
Through  being  bitten,  or  otherwise  receiving 
the  equine  mucus  or  saliva,  man  may  be 
infected  and  also  probably  by  eating  the  raw 
flesh  of  an  infected  animal.  In  man,  glanders 
and  farcy  generally  occur  together  instead  of 
separately  as  in  the  horse.  Knackers,  how- 
ever, possess  a  remarkable  immunity  to 
glanders.  Actinomycosis  (ray  fungus)  is  a 
streptothrix  —  one  of  the  higher  forms  of 
bacteria.  In  cattle  it  produces  "  lumpy  jaw  " 


26 


BAG 


MUNICIPAL   AND    SANITAEY  ENGINEERING. 


BAC 


and  "  wooden  tongue  "  and  is  communicable 
to  man.  It  is  epiphytic  on  cereals  and  straw, 
which  probably  communicate  it  to  animals. 
Madura  disease  in  its  black  variety  is  due  to  a 
streptothrix. 

Quarter-evil,  foot  and  mouth  disease,  and 
swine  fever  are  also  due  to  micro-organisms. 

DISEASES  DUE  TO  OTHER  MICRO-ORGANISMS. — 
Malaria  is   caused   by  a  protozoan  parasite, 
the   Plasmodium    malaria.      Ic    is    conveyed 
by    mosquitoes    belonging    to    the    Anophe- 
linae.      In    the    body  of    the   insect   and   in 
the    blood    of    the    host,    it    goes    through 
a    long     cycle     of     changes.       Prophylactic 
measures  deal  chiefly  with  the  exclusion  of 
mosquitoes  and  the  destruction  of  their  larvae, 
which  are   deposited   in   stagnant   pools,  by 
draining  and  covering  the  surface  of  the  pools 
with  petroleum  or  insoluble  tar  oils.     Sleeping 
sickness  is  considered  to  be  caused  by  Try- 
panosoma  ganibiense,    a    protozoan    organism 
carried  by  a  tsetse  fly.     A  trypanosome  (TV. 
Brucei)  is  found  in  nagana  (tsetse  fly  disease 
of  horses)  and  another  in  Surra.     A  trypano- 
some is  a  spindle-shaped  organism,  with  an 
undulating   membrane   at    the   side   and   an 
anterior  flagellum.     Tropical  dysentery  is  due 
to  amoebae.     Infection  takes  place  from  water 
and  green  vegetables.     The  hyphomycetes  are 
generally    non  -  pathogenic,    but    Aspergillus 
niger,  the  ringworm   fungi,  and  Oidium  albi- 
cans  are  pathogenic,  the  latter  causing  the 
white   patches   occurring   in   the   mouths   of 
infants    suffering   from    thrush.     Syphilis   is 
attributed  to  a  spirochaeta  (a  spiral  filiform 
parasite    with    no    flagella,    but    having    an 
undulating  movement)  known  as  Treponema 
pallidum.   The  aetiology  of  carcinoma,  sarcoma, 
hydrophobia,  and  small-pox  is  uncertain,  but 
probably  the  last  two  are  caused  by  protozoa. 
There   is   sufficient   evidence   to  warrant   an 
assumption  that  damp  houses  are  a  factor  in 
the  production  of  cancer.     It  is  possible  that 
the  infective  agent  (if  such  there  be)  exists  in 
uncooked   fruit   and    vegetables.     Acari  and 
microscopic  eels  may  also  have  something  to 
do  with  the  infection. 

W.  P. 

27 


Bacteria  Beds. — (See  "SEWAGE  DISPOSAL.") 

Bacteriological  Examination  of  Disin- 
fectants. -  -  Influences    affecting    Germicidal 
Value  —  The    Carbolic    Acid   Coefficient  —  The 
Garnet    Method  —  The    Thread    Method  —  The 
Rideal-Walker  or  Drop  Method — The  Influence 
of   Organic   Matter  —  The    Sommerville- Walker 
Coefficient. — As  the  function  of  a  disinfectant 
is    to    kill    micro-organisms,    it    is    obvious 
that  the  proof  of  such  capability  by  labora- 
tory experiments    indicates    its   value   in    a 
way   that   chemical  analysis  never  can.     In 
the    case    of    some     coal     tar    disinfectants 
chemical  analysis  is  absolutely  useless  as  a 
measurer    of    germicidal    power,    this   being 
to  a  large  extent  dependent  on  physical  con- 
ditions not  indicated  by  chemistry.     In  prac- 
tice bacteria  are   met  with  in   conditions  of 
varying  vitality  and  environment.     Some  of 
these  conditions  cannot  be  properly  simulated 
in  a  laboratory  test,  but  by  the  introduction 
of  various  forms  of  organic   matter  we  are 
able   to   ascertain  with  a  reasonable   degree 
of  accuracy  what  conditions  will  diminish  the 
value  of  the  disinfectant.     It  is  first  necessary 
to  ascertain  the  action  of  the  disinfectant  on 
"naked"  bacteria,  i.e.,  bacteria  unprotected 
by  any  large  quantity  of  organic  matter,  and 
then  to  incorporate  in  the  test  organic  matter 
likely  to  be  met  with  in  practice,  and  find  if 
any  depreciation  has  occurred. 

The  statements  often  seen  to  the  effect  that 
a  certain  disinfectant  when  used  in  a  particular 
dilution  will  kill  a  certain  organism  in  a 
specified  time  may  be  regarded  as  fallacious. 
Such  tests  are  performed  by  adding  to  the 
diluted  disinfectant  a  few  drops  of  a  bacterial 
culture,  and  at  the  end  of  certain  periods 
transferring  a  loopful  of  the  contaminated 
disinfectant  to  a  tube  of  sterile  broth,  labelling, 
and  incubating.  A  growth  (which  gives  the 
broth  a  turbid  appearance)  shows  that  when 
the  "sub-culture"  was  made  from  the  con- 
taminated disinfectant  the  bacteria  were  still 
alive.  If  death  had  occurred  no  growth  would 
have  taken  place  in  the  "  sub-culture,"  and 
the  broth  would  have  remained  clear.  Such 


BAC 


ENCYCLOPAEDIA  OF 


BAC 


results  are  worthless  for  the  following  reasons  : 
Even  bacteria  of  the  same  species  do  not 
possess  an  identical  resistance  to  disinfection. 
The  number  of  organisms  that  will  be  killed 
by  a  given  quantity  of  disinfectant  is  limited, 
and  the  velocity  of  disinfection  also  depends 
on  their  resistancy  or  age.  When  first 
brought  in  contact  with  the  disinfectant  the 
mortality  of  the  bacteria  is  large  but  gradually 
becomes  slower,  and  when  a  curve  is  plotted 
with  the  numbers  of  surviving  bacteria  as 
ordinates  and  the  corresponding  times  as 
abscissae,  it  is  hyperbolic  in  form.  The  tem- 
perature of  the  disinfectant  during  the  period 
of  contact  (the  medication  temperature)  affects 
the  result  considerably,  a  rise  of  two  or  three 
degrees,  especially  above  the  optimum  tempera- 
ture for  the  growth  of  the  organism,  very 
appreciably  increasing  the  power  of  the  disin- 
fectant. Similarly  a  culture  which  has  been 
incubated  at  a  temperature  favourable  to  the 
growth  will  be  more  resistant  than  one  grown 
at  a  less  satisfactory  temperature.  The  same 
remark  applies  to  the  reaction  and  constituents 
of  the  culture  medium. 

THE  CARBOLIC  ACID  COEFFICIENT.  —  In 
1896  Moor  suggested,  in  order  to  obtain 
some  trustworthy  datum  of  the  germicidal 
value  of  a  disinfectant,  that  at  the  same  time 
as  it  was  tested,  a  solution  of  some  trustworthy 
disinfectant  should  also  be  tested  under  the 
same  conditions.  This  allows  a  comparison 
between  them.  Carbolic  acid  (phenol)  is  the 
standard  disinfectant  usually  selected  for  this 
purpose  as  it  can  be  accurately  standardised. 
(Mercuric  chloride  is  less  satisfactory  and  its 
antiseptic  effect  in  the  sub-cultures  is  so 
marked  that  it  is  necessary  to  add  to  the 
sub-culture  tubes  some  sulphuretted  hydrogen 
water  to  convert  it  into  an  inactive  sulphide.) 
Such  an  expression  of  germicidal  activity  is 
known  as  "  the  carbolic  acid  coefficient."  As 
will  be  seen  when  considering  the  Kideal- 
"Walker  test,  this  method  provides  for  the 
simultaneous  examination  of  a  standard 
carbolic  acid  solution,  and  when  a  strength 
of  the  disinfectant  under  examination  is  found 
to  kill  the  test  organism  in  the  same  time  and 


at  the  same  time  as  the  control  carbolic  acid, 
it  is  evident  that  the  two  strengths  allow  of 
comparison.  Thus  should  a  1  in  250  solution 
of  a  disinfectant  X  allow  of  growth  up  to  5 
minutes  and  kill  in  7£  minutes,  and  a  1  in  100 
solution  of  phenol  give  life  and  death  in  the 
same  periods,  the  carbolic  acid  coefficient  of 
X  would  be  f  gg  =  2'5.  Reference  to  a  chart 
of  a  test  given  later  will  further  explain  this. 
Carbolic  acid  coefficients  obtained  by  different 
methods  often  differ,  and  workers  not  adhering 
strictly  to  the  modus  operandi  with  the  same 
test  also  obtain  unsatisfactory  results.  Hence 
when  the  precise  technique  of  the  Eideal- 
Walker  test  has  been  followed,  it  is  customary 
to  specify  the  same  by  calling  the  carbolic 
acid  coefficient  so  obtained  the  Ilideal-Walk<T 
Coefficient. 

As  tests  on  naked  germs,  three  methods 
have  been  put  forward :  the  Garnet,  Thread, 
and  Eideal-Walker  methods. 

THE  GARNET  METHOD. — In  this  test,  devised 
by  Kronig  and  Paul,  the  culture  of  the  test 
organism  is  dried  on  garnets  the  size  of  a  pea. 
The  garnets  with  the  covering  of  the  test 
organism  are  soaked  in  solutions  of  the  disin- 
fectant for  known  periods  of  time,  when  they 
are  removed,  well  washed  with  sterile  water, 
and  then  dropped  into  broth  tubes.  A  carbolic 
acid  control  is  introduced,  but  the  test  is  very 
liable  to  error  since  the  organism  as  well  as 
the  disinfectant  may  be  removed  in  the 
washing. 

THE  THREAD  METHOD. — An  emulsion  of  an 
agar  culture  in  sterile  water  is  made,  and 
sterilised  silk  threads  are  soaked  in  the  filtered 
emulsion  for  an  hour  and  then  dried.  Four 
dilutions  of  the  disinfectant  and  one  of  the 
control  are  placed  in  thirty  water  watch  glasses, 
each  dilution  being  put  into  six  watch  glasses. 
An  infected  thread  is  placed  in  each  watch 
glass,  and  from  each  different  dilution  an 
infected  thread  is  taken  at  the  end  of  every 
2^  consecutive  minutes  up  to  15  minutes, 
well  washed  with  sterile  water  and  placed  in 
a  broth  sub-culture  tube.  The  difficulty  of 
washing  away  the  disinfectant  without  remov- 
ing the  organism  renders  the  results  very 


28 


BAG 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


BAC 


unsatisfactory,  and,  like  the  Garnet  method, 
it  is  eminently  unfitted  for  working  with 
organisms  at  all  sensitive  to  desiccation. 

THE  RIDEAL-WALKEK  METHOD  (The  Drop 
Method). — This  test  has  been  adopted  by 
most  bacteriologists,  disinfectant  manufac- 
turers, and  large  users  of  disinfectants,  as  a 
standard  method,  the  process  being  un- 
doubtedly the  most  satisfactory  hitherto 
devised.  A  special  test-tube  rack  is  desir- 
able, having  two  tiers,  the  upper  for  six 
sets  of  five  tubes  for  sub-cultures  and  the  lower 
tier  with  five  holes  for  four  medication  tubes 
of  the  disinfectant  and  one  of  the  control. 
The  broth  tubes  in  the  upper  tier  are  numbered 
from  1  to  30.  The  test  is  usually  performed 
on  a  broth  culture  of  the  typhoid  bacillus, 
which  after  inoculation  has  been  incubated 
for  24  hours  at  blood  heat.  Other  organisms 
may  also  be  used,  and  it  should  be  here 
remarked  that  disinfectants  show  a  marked 
selective  action  on  bacteria,  the  latter  being 
more  sensitive  to  one  disinfectant  than  to 
another  when  both  disinfectants  may  have  an 
equal  effect  on  bacteria  of  another  species. 

The  inoculating  needle  has  a  loop  of  3mm. 
diameter,  the  centre  part  of  the  loop  being 
bent  down.  The  standard  carbolic  acid  is 
best  kept  as  a  5%  solution,  which  has 
been  standardised  by  the  bromine  method. 
The  requisite  dilutions  for  controls  are  made 
from  this. 

The  broth  recommended  by  Rideal  and 
Walker  for  cultures  and  sub-cultures  has  the 
following  composition : 

Lemco  .  .  20  grammes 
Peptone  (Witte)  .  20  grammes 
Salt  .  .  .10  grammes 
Distilled  water  to  1  litre. 

It  is  directed  to  boil  the  mixture  for  30 
minutes,  filter,  neutralise  with  normal  sodium 
hydrate  solution,  using  phenolphthalein  as 
an  indicator,  and  when  neutral,  to  add  15  c.c. 
of  normal  hydrochloric  acid.  This  gives  an 
acid  reaction  of  +  1*5  per  cent.  (+  15  Eyre's 
scale).  The  broth  culture  used  should  be  free 
from  clumps.  This  may  be  attained  by 


running  the  culture  through  a  sterile  filter 
paper,  or,  as  will  be  found  more  convenient, 
after  agitation  of  the  tube,  allowing  it  to  stand 
for  20  minutes  before  use,  when  the  clumps  will 
settle  to  the  bottom  and  need  not  be  disturbed 
when  pipetting  the  culture  into  medication 
tubes.  As  the  number  and,  consequently,  the 
resistance  of  the  organism  probably  differs 
according  to  the  method  adopted  for  the 
removal  of  the  clumps,  one  process  should  be 
adhered  to  so  that  the  culture  will  not  vary 
much  from  day  to  day.  All  pipettes,  measures, 
and  test-tubes  must  be  sterile. 

The  temperature  of   the  room  should   be 
noted  and  the  strength  of  carbolic  acid  used 
as  a  control  altered  to  suit.     (When  working 
with  an  organism    of    unknown    strength  a 
"  phenol  table  "  should  be  made  in  which  five 
strengths  of  phenol  are  tested  in  the  same 
way  as  when  a  disinfectant  is  the  subject  of 
the  test.     Then  a  strength  should  be  selected 
which  gives  "  life  "  at  2£  and  5  minutes  and 
"  death  "  at  7£,  10, 12£,  and  15  minutes.)   Five 
sterile  test-tubes,  plugged  with  cotton  wool,  are 
placed  in  the  lower  tier  of  the  test-tube  rack. 
Three  c.c.  of  four  dilutions  of  the  disinfectant 
(made  with  distilled  water)  are  put  into  the  first 
four  and  the  same  amount  of  the  control  in  the 
fifth.     Into  each  in  succession,  at  intervals  of 
30  seconds,  three  drops  of  typhoid  culture  are 
pipetted,  the  tubes  being  agitated  to  disperse 
the  bacteria  through  the  disinfectant.     Half  a 
minute  after  the  fifth  inoculation,  a  loopful  is 
taken  from  the  first  medication  tube  and  placed 
in  the  broth  tube  marked  "  1."     This  process 
is  repeated  at  intervals  of  30  seconds  with  the 
other  medication  tubes  until  the  first  five  sub- 
culture tubes  have  been  inseminated.     (These 
will  subsequently  show  whether  an  exposure 
to  disinfectant  of  2^  minutes  has  been  sufficient 
to  kill  the  organism.)     At  the  time  when  the 
first  sub-culture  from  the  fifth  medication  tube 
is  made,  the  organism  in  the  first  tube  will 
have  been  exposed  for   4£  minutes   and    30 
seconds  later  this  is   inoculated   into   broth 
tube  "  6,"  and  so  on  until  all  the  sub-culture 
tubes  have  been  inoculated.     As  the  tubes  are 
inoculated  they  are  placed  in  a  wire  basket 
29 


BAC 


ENCYCLOPAEDIA  OF 


BAG 


and  are  subsequently  incubated  for  three  days 
at  37°  C.  They  are  then  replaced  in  the  test- 
tube  rack  and  the  results  observed  and  charted. 
The  results  of  an  actual  test  are  given  below : 


o 


O 

m 

H 
i 

pq 


g 

1 

o 

0. 

o              .... 

t- 

eo 

g 

1 

E 
g 

c 

"3 

.2 

0 

g^ 

2 

as 

a 

BQ 

E 

§        s       r       r       , 

*o 

•^ 

1 

t- 

5 

I 

S 

111      + 

J 

D 

^ 

1 

c 

c? 

I        1      + 

2 

4 

•5 

) 

c 

3 

a 

0 

1      +     + 

3 

"S  8 

4 

i 

-2a 

LI 

3 

|'i 

J? 

1        1      +     + 

9 

o 

H 

A 

1 

£ 

1 

C 

.£ 

>o 

+     +     +     + 

f 

~s 
o 

I 

B 

C4 

1      +     +     +     + 

c 
- 

0        O        O        O        0 

<M        ^        CD         00        C-I 

TH        cq        CO        TH        TH 

r^ 

'3 

a 

<3 

1 

1 

:      :      :      :    1 

!*!     .M      !*!      M      0 

o 
O 


Certain  disinfectants  when  diluted  separate 
out  into  layers,  having  very  varied  germicidal 
powers.  As  such  disinfectants  if  made  up  a 
day  or  so  before  use  are  liable  to  produce  a 
false  sense  of  safety,  the  authors  of  the 
Eideal-Walker  test  have  requested  that  a 
1%  solution  of  the  disinfectant  under  exami- 
nation should  be  made  up  24  hours  before 
testing,  and  the  further  dilutions  made  from 
this. 

The  results  obtained  by  the  Rideal- Walker 
process  only  show  the  value  of  a  disinfectant 


when  possible  militating  organic  matter  is 
practically  absent.  It  has  served  and  still 
serves  the  very  useful  purpose  of  eliminating 
disinfectants  which  are  practically  devoid  of 
germicidal  power.  But  it  does  not  exclude 
the  hypochlorites,  permanganates  and  other 
disinfectants  dependent  for  their  germicidal 
powers  on  an  oxidising  action,  which  action  is 
preferentially  expended  on  dead  matter  rather 
than  on  bacteria.  Various  forms  of  organic 
matter  have  been  suggested  for  incorporation 
in  the  test.  Hewlett  and  Kenwood  used 
fasces  and  the  Lister  Institute  also  recom- 
mend a  3  %  emulsion  of  dried  and  ground 
faeces  for  the  purpose.  This  excretion  varies 
so  enormously  in  composition  that  its  intro- 
duction into  a  standard  test  causes  hopelessly 
erratic  results,  and  the  plea  that  it  represents 
animal  matter  requiring  to  be  disinfected  in 
practice  is  put  out  of  court  owing  to  the  im- 
possibility of  disinfecting  stools  by  chemical 
means  alone  ;  moreover  the  fasces  as  used  in 
the  test  bear  no  resemblance  to  the  article 
met  with  in  practice.  Milk  has  also  been 
suggested  as  a  suitable  material,  but  the  fat 
globules  exercise  a  protective  influence  over 
the  bacteria  in  a  way  that  no  other  material 
likely  to  require  disinfection  does.  Urine  on 
the  other  hand  has  constantly  to  be  disin- 
fected, and  its  incorporation  in  the  test  as 
a  diluent  in  the  place  of  distilled  water  serves 
to  bring  down  the  "  false  coefficients  "  of  the 
oxidising  disinfectants. 

Sommerville  and  Walker  have  emphasised 
the  necessity  of  using  separately  certain 
simple  organic  substances.  They  first  of  all 
dilute  the  disinfectant  with  water,  in  the  pro- 
portion recommended  by  the  manufacturers, 
and  make  the  further  dilutions  with  1  °/0 
solutions  of  blood  serum,  mucin,  peptone, 
casein,  gelatine,  blood,  or  with  whole  urine. 
The  disinfectant  is  then  allowed  to  remain  in 
contact  with  the  organic  matter  for  one  hour 
before  adding  the  test  organism.  This  in 
some  degree  simulates  the  conditions  met  with 
in  practice  where  a  disinfectant,  soon  exhausted 
on  organic  matter,  offers  no  further  opposition 
to  further  additions  of  infected  material.  In 


30 


BAC 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BAC 


the  case  of  the  oxidising  disinfectants  the 
germicidal  power  wasted  on  the  organic  matter 
is  obviously  lost,  but  when  a  lowering  of  the 
coefficient  occurs  writh  the  coal-tar  disinfect- 
ants, it  is  thought  by  some  observers  that 
tli is  does  not  necessarily  indicate  a  deprecia- 
tion of  the  disinfectant.  It  is  possible  that 
the  disinfectant  carried  down  by  sputum  or 
other  organic  matter,  may  still  be  capable  of 
continued  action.  To  meet  the  influence  of 
absorption,  Sommerville  and  Walker  have  in- 
troduced participate  matter  in  the  form  of 
granules  of  rice  starch.  The  diluent  consists 
of  water  and  animal  and  vegetable  matter 
consisting  of  0*5  %  of  gelatine,  in  solution,  and 
0'5%of  rice  starch  (in  suspension).  Results 
obtained  with  this  diluent  are  known  as  the 
Sommerville-  Walker  coefficients. 

In  all  forms  of  disinfection, Defries's  "factor 
of  safety  "  must  be  recognised.  Sommerville 
and  Walker  suggest  that  "  it  might  be  insisted 
that  the  multiple  5  be  applied  as  a  minimum 
to  the  strengths  of  the  various  disinfectants 
which  are  found  to  perform  the  same  work  as 
1  in  100  phenol."  W.  P. 

Bacteriology  of  the  London  Water 
Supply. — Sources — Districts — Works — Results 
(raw  waters,  stored  waters,  filtered  waters, 
number  of  bacteria,  B.  coli  test,  type  of  B.  coli 
&c.,  remarks) — Research  Work — Reports — Sum- 
mary and  Conclusions. 

1.  SOUKCES. — The    sources    of    the   Water 
Board's  supply  are  from  (1)  the  River  Thames 
(about  52%);  (2)  the  River  Lea  (about  23%) ; 
and  wells  and  springs  (about  25  %). 

2.  DISTRICTS. — The  administrative  districts 
of    supply  are    as  follows : — Eastern,    Kent, 
New   River,    Southern    and   Western    (total 
population,  nearly  seven  millions). 

3.  WORKS. — From    the    point    of    view   of 
quality  of  water,  the  Water  Board's  supply  is 
best    considered    as    the   following   separate 
waterworks : — 

(1)  East  London  (Clapton,  Lea  Bridge) 
nitration  works  (i.e.,  Lea  water  mixed  with 
some  well-water,  after  prolonged  storage  in 


31 


the  Walthamstow  reservoirs;  also  some  well- 
water). 

(2)  Sunbury    (Hanworth)   filtration  works 
(i.e.,  River  Thames  water  after  settlement  and 
passing  through  roughing  filters ;  also  gravel 
or  spring  water). 

(3)  Kempton    Park    filtration    works    (i.e., 
chiefly  Thames  water  after  prolonged  storage 
in  reservoirs  at  Staines  and  Kempton  Park). 

(4)  New  River  (Hornsey)  filtration  works. 

(5)  New  River  (Stoke  Newington)  filtration 
works. 

(6)  New  River  (Clerkenwell)  filtration  works 
(i.e.,  mixed  Lea  (New  River)  and  well-water, 
slight  storage  in  Hornsey  and  Stoke  Newing- 
ton storage  reservoirs). 

(7)  Southwark    and    Vauxhall    (Hampton 
and  Sunnyside)  filtration  works  (i.e.,  Thames 
water,  mostly  after  storage  in  reservoirs  at 
Walton  and  Hampton  ;  also  gravel  water). 

(8)  Lambeth    (Surbiton)    filtration    works 
(i.e.,  Thames  water  after  storage  in  reservoirs 
at  Molesey;  also  gravel  water). 

(9)  Grand    Junction  (Hampton)    filtration 
waterworks  (i.e.,  Thames  water  after  storage 
in  reservoirs  at  Staines  and  Hampton  ;  also 
gravel  water). 

(10)  Grand  Junction  (Kew)  filtration  water- 
works  (i.e.,  Thames  water   after   storage   in 
reservoirs  at  Staines  and  Hampton). 

(11)  West    Middlesex    (Barnes)     filtration 
works  (i.e.,  Thames   water   after   storage   in 
reservoirs  at  Staines  and  Barnes). 

(12)  Chelsea    (Surbiton)    filtration    works 
(i.e.,  Thames  water  after  storage  in  reservoirs 
at  Molesey  ;  also  gravel  water). 

(13)  Lea  Valley  wells  (some  of  these  are 
pumped    into    the    Lea     and     New    River, 
and     some     are     used     directly    for    supply 
purposes). 

(14)  Kent  wells  (all  used  directly  for  supply 
purposes). 

(15)  Additional  wells    (Streatham,    Honor 
Oak,  Selhurst,  &c.). 

(1),  (2),  and  sometimes  (3).     Used  for  the 
supply  of  the  Eastern  district. 

(4),  (5),  and  (6).     Used  for  the  supply  of 


BAG 


ENCYCLOPAEDIA   OF 


BAC 


the  New  River  district,  and  (3)  really  belongs 
to  this  district. 

(7)  and  (8).  Used  for  the  supply  of  the 
Southern  district. 

(9),  (10),  (11),  and  (12).  Belong  to  the 
Western  district. 

(13).  Supplies  both  the  Eastern  and  New 
River  districts. 

(14).  Supply  to  the  Kent  district. 

(15).  Augments  the  supply  to  the  Southern 
district. 

4.  RESULTS. — The  results  as  regards  the 
bacteriological  quality  of  the  water  during 
the  twelve  months  ended  March  31st,  1908 
(unless  otherwise  stated),  will  be  considered 
under  the  following  headings : — (1)  Raw 
waters  ;  (2)  stored  waters  ;  (3)  filtered  waters 
and  unfiltered  well-waters. 

(1)  RAW  WATEES. — Average  total  number  of 
microbes  per  c.c.  (gelatine  at  20 — 22°  C., 
colonies  counted  on  third  day).  Thames, 
3,170;  Lea,  6,707  ;  New  River,  1,639. 

Average  number  of  microbes  per  c.c.  (agar  at 
37°  C.,  colonies  counted  on  second  day). 
Period  of  twelve  months  ended  July  31st, 
1908.  Thames,  280;  Lea,  382;  New  River, 
88. 

Average  number  of  microbes  per  c.c.  (lactose 
bile-salt  agar  at  37°  C.,  colonies  counted  on 
second  day).  Period  of  twelve  months  ended 
July  31st,  1908.  Thames,  41 ;  Lea,  34 ;  New 
River,  8. 

B.  coli  test: — 

PER  CENT.  OF  SAMPLES  CONTAINING  : — 


1  or 

10  or 

100  or 

1,000  or 

10,000  or 

more 

more 

more 

more 

more 

B.  coli. 

B.  coli 

B.  coli 

B.  coli 

B.  coli 

per  c.c. 

per  c.c. 

per  c.c. 

per  c.c. 

per  c.c. 

% 

% 

/o 

% 

A> 

River  Thames 

83-2 

46-8 

8-8 

0-4 

River  Lea 

90'8 

46-8 

10-4 

2-4 

0-4 

New  River 

49-6 

14-4 

1-6 

— 

— 

It  will  be  seen  that  the  raw  waters  contain 
a  large  number  of  bacteria,  many  of  which 
grow  at  blood  heat,  and  not  a  few  in  a  bile- 
salt  medium.  Further,  nearly  one-half  of 


the  Thames,  Lea,  and  New  River  samples 
contain  at  least  10,  10  and  1,  B.  coli  per  c.c. 
respectively. 

(2)  STORED  WATERS. — As  examples  of  stored 
water  the  Chelsea,  Lambeth,  and  Staines 
(Thames  water),  and  Lea  (Lea  water)  stored 
water  results  may  be  given.  The  nominal 
number  of  days'  storage  being  about  fifteen, 
fourteen,  ninety-five,  and  fifty-eight  respec- 
tively. 

Average  total  number  of  microbes  per  c.c. 
(gelatine  at  20 — 22°  C.,  colonies  counted  on 
third  day).  Chelsea  stored  water,  208 ; 
Lambeth  stored  water  (ten  months'  average), 
362  ;  Staines  stored  water,  175  ;  Lea  stored 
water,  67. 

Average  number  oj  microbes  per  c.c.  (agar  at 
37°  C.,  colonies  counted  on  second  day). 
Twelve  months  ended  July  31st,  1908.  Chel- 
sea stored  water,  44 ;  Lambeth  stored  water 
(ten  months'  average),  52 ;  Staines  stored 
water,  34  ;  Lea  stored  water,  11. 

Average  number  of  microbes  per  c.c.  (lactose 
bile-salt  agar  at  37°  C.,  colonies  counted  on 
second  day).  Twelve  months  ended  July  31st, 
1908.  Chelsea  stored  water,  5 ;  Lambeth 
stored  water  (ten  months'  average),  8 ;  Staines 
stored  water,  2  ;  Lea  stored  water,  0'6. 

B.  coli  test: — 

PER  CENT.  OF  NEGATIVE  AND  POSITIVE  RESULTS. 


Stored 
Waters. 

Negative. 

Positive. 

100 

100 

10 

i 

o-i 

o-oi 

c.c. 

c.c. 

c.c. 

c.c. 

c.c. 

c.c. 

Cols.  1 

2 

3 

4 

5 

6 

7 

Chelsea. 

42-7 

24-7 

19-1 

10-1 

2-2 

1-1 

(13-4)* 

Lambeth. 

16-2 

32-5 

27-5 

16-2 

7-5 

(23-7)* 

Staines. 

337 

33-7 

22-9 

9-6 

(9-6;* 

Lea. 

67-4 

26-9 

4-5 

1-1 

(1-1)* 

*  The  figures  in  brackets  are  the  aggregates  of  col'iinns  o,  <>,  and  7. 

The  enormous  bacteriological  improvement 
in  the  raw  water  as  the  result  of  storage  is 


32 


BAC 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BAC 


well  shown  by  the  foregoing  figures.  For 
example,  83'2  %  of  the  raw  Thames  samples 
contained  B.  coli  in  1  c.c.  of  water.  The  cor- 
responding figures  for  the  Chelsea,  Lambeth, 
and  Staines  stored  water  were  13'4,  23'7,  and 
9'6  respectively.  In  the  case  of  the  Lea  the 
figures  are  still  more  remarkable,  as  90'8% 
of  the  raw  Lea  samples  contained  B.  coli  in 
1  c.c.,  whereas  the  corresponding  figure  for 
the  Lea  stored  water  is  only  I'l  °/0.  As  regards 
the  latter  water  over  two  -  thirds  of  the 
samples  actually  contained  no  B.  coli,  even 
in  100  c.c. 

Streptococcus  test. — The  raw  waters  are  also 
examined  for  streptococci,  but  these  microbes 
are  nearly  always  absent  from  1  c.c.  of  the 
samples. 

(3)  FILTERED  WATERS  (AND  UNFILTERED  WELL- 
WATERS). — Average  total  number  of  microbes 
per  c.c.  (gelatine  at  20  —  22°  C.,  colonies 
counted  on  third  day).  It  sometimes  happens 
that  samples  of  the  filtered  water  collected  from 
the  separate  filter  wells  at  the  works  contain 
an  enormous  number  of  bacteria.  The  great 
majority  of  these  microbes,  however,  are 
believed  to  be  harmless,  and  not  to  be  asso- 
ciated with  imperfect  filtration.  To  include 
chese  figures  in  the  averages  would  create  an 
erroneous  impression,  and  so  all  samples 
containing  100  or  more  microbes  per  c.c. 
have  been  excluded  from  the  averages  given 
underneath : — 

Average  Number  of 
Microbes  per  c.c. 

(exclusive  of  those 
Samples  contain- 
ing 100  or  more). 

1.  East  London  (Lea) 

2.  Sunbury     (Hanworth).        Eesults     for 

1907 — 8  not  available. 

3.  Kempton  Park 

4.  5  &  6.     New    Elver    (Hornsey,    Stoke 

Newington,  Clerkenwell) 

7.  Southwark  and  Vauxhall 

8.  Lambeth 

9  &  10.     Grand  Junction  (Hampton,  Kew) 

11.     West  Middlesex 

Chelsea 

Lea  Valley  Wells  (excepting  Eye  Com- 
mon  and  Amwell  Hill),  March,  1906, 

to  March  31st,  1908 

14.     Kent  Wells 


12. 
13. 


25-3 

5-7 
12-7 

6-7 
11-2 

9-2 

6-3 


8-4 
5-6 


The  following  statement  indicates  that  the 
exclusive  figures  for  the  filtered  waters  were 
small,  and  the  percentage  reduction  effected 
by  the  processes  of  subsidence  and  filtration 
remarkably  good : — 


Thaaies. 

Lea. 

New  River. 

Haw  waters 

(microbes  per  c.c.) 

3,170 

6,707 

1,639 

Filtered  waters 

(microbes  per  c.c.) 

11-1 

13-6 

5-7 

Percentage   reduc- 

tion 

99-6 

99-7 

99-6 

B.  coli  test. — The  percentage  number  of 
samples  containing  no  B.  coli,  even  in  100  c.c. 
of  water,  was  as  follows  : — 


Percentage  Number 
of  Samples  contain- 
ing no  B.  coli  even 
in  100  c.c.  of  water. 


1. 
2. 

3. 
4,  5 


East  Tendon  (Lea) 

Sunbury     (Hanworth).     Eesults 

1907 — 8  not  available. 
Kempton  Park 


for 


&  6.     New  Eiver  (Hornsey,    Stoke 
Newington,  Clerkenwell) 

7.  Southwark  and  Vauxhall 

8.  Lambeth 

9  &  10.  Grand  Junction  (Hampton, 
Kew) 

West  Middlesex  

Chelsea 

Lea  Valley  Wells  (excepting  Eye 
Common  and  Amwell  Hill),  March, 
1906,  to  March  31st,  1908 

Kent  Wells 


11. 

12. 
13. 


14. 


85-9 


90-1 

83-8 
67-2 

79-7 

79-0 
82-0 

871 


92-0 
90-2 


The  remarkable  improvement  in  the  raw 
waters  effected  by  the  processes  of  storage  and 
filtration  may  be  judged  by  the  statement 
that  whereas  the  majority  of  the  raw  water 
samples  contain  B.  coli  in  1  c.c.,  only  a 
minority  of  the  filtered  water  samples  contain 
this  microbe  in  one  hundred  times  as  much 
water. 

Type  of  B.  coli. — As  regards  the  type  of  B. 
coli  in  the  raw  and  filtered  waters,  the  following 
table  shows  that  the  filtered  waters  contain  pro- 
portionately (as  well  as  actually)  fewer  typical 
B.  coli  than  the  raw  water. 


M.S.E. 


33 


BAC 


ENCYCLOPEDIA   OF 


BAL 


TYPE  OF  B.  COL/. 


Maw  Waters. 

Filtered  Waters. 

Out  of  2,710  speci- 

Out of  3,830  speci- 

mens   of    li.     coli 

mens     of     B.    coli 

isolated    from    750 

isolated  from  7,797 

samples     of     raw 

samples   of  filtered 

water  the  propor- 

water      (including 

tion    between    the 

Kent     and     Lea 

Type  of  B.  coli. 

typical    and   non- 

Valley       unfiltered 

typical     races     of 

\vel  1  -water),  the  pro  • 

B.    coli    expressed 

portion  between  the 

as  percentages  was 

typical     and     non- 

as  follows  :  — 

typical     races     of 

B.    coli,    expressed 

as  percentages,  was 

as  follows  :  — 

Typical  B.  coli  : 

(+  lactose  ;  -j-  indol) 

81'6 

54-4 

Non-typical  B.  coli  : 

(+  lactose  ;  -  indol) 
(  -  lactose  ;  -)-  glucose) 

8-9  !18'3 

21-1  )  ., 
24-4  )  45>5 

5.  EESEAKCH  WORK. — A  great  deal  of  re- 
search work  is  carried  out  at  the  Water 
Board's  Laboratories.  As  yet  (1908),  however, 
only  two  special  reports  have  been  published 
on  (1)  "  The  vitality  of  the  typhoid  bacillus  in 
artificially  infected  samples  of  raw  Thames,  Lea 
and  New  River  water,  with  special  reference  to 
the  question  of  storage,"  and  (2)  on  "  The  nega- 
tive results  of  the  examination  of  samples  of  raw 
Thames,  Lea  and  New  River  water  for  the 
presence  of  the  typhoid  bacillus."  As  regards 
the  former,  the  reduction  in  the  number  of  the 
artificially  added  typhoid  bacilli  was  over 
99  %  within  a  period  of  one  week,  in  all 
the  eighteen  laboratory  experiments.  A  few 
of  the  typhoid  bacilli,  however,  remained 
alive  for  from  four  to  eight  weeks.  As  regards 
the  latter,  294  experiments  were  made  with 
156  samples  of  raw  river  water.  The  total 
amount  of  water  dealt  with  was  29,400  c.c., 
containing  in  the  aggregate,  nearly  136 
million  bacteria.  7,329  microbes  were 
specially  studied,  but  none  of  them  proved 
to  be  the  typhoid  bacillus.  These  7,329 
microbes  formed  but  a  small  fraction  of  the 
millions  of  the  other  bacteria  which  were 
excluded  owing  to  the  temperature  of  in- 
cubation, the  composition  of  the  media 
employed,  and  the  fact  of  their  appearing 
one  the  plate  cultures  as  coloured  colonies. 


Undue   importance,  however,    must    not    be 
attached  to  negative  results. 

6.  REPORTS. — Reports  as  to  the  quality    of 
the  London  waters  are  made  each  month,  and 
are  incorporated  in  the ''Monthly  Reports"  of 
the  Government  Water  Examiner,  appointed 
under     the     Metropolis     Water    Act,    1871. 
Yearly   and   special   reports   are   also   issued 
from  time  to  time  by  the  Water  Board.     The 
former  may  be  obtained  from  the  publishers 
for  the  time  being  of  Government  Publica- 
tions, and  the  latter  from  the  Central  Office 
of  the  Water  Board,  at  Savoy  Court,  W.C. 

7.  SUMMARY  AND  CONCLUSIONS. — The  Water 
Board    supplies    a    population    of    nearly  7 
million  persons.      The  supply  is  derived  from 
the   River  Thames  (rather   more   than   one- 
half)  ;  River  Lea   (nearly  one  quarter)  ;   and 
wells  and  springs  (about  one  quarter). 

Speaking  generally :  — 

(1)  The  raw  waters  on  an  average  contain 
between  1,000  and  10,000  microbes  per  c.c.  ; 
the  filtered  and  well-waters  between  10  and 
100. 

(2)  The  majority  of  samples  of  raw  water 
contain   B.   coli   in    1    c.c.  ;    the  minority  of 
samples  of  the  water  actually  sent  into  supply, 
contain  B.  coli  in  100  c.c.     These  results  are 
based    on  the  results  of  the  examination  of 
between  eight   and   nine   thousand   bacterio- 
logical samples  yearly.     The  practice  of  the 
Water  Board  now  is  to  store  all  river  water,  as 
far  as  this  is  practicable,  antecedent  to  filtra- 
tion.    There  are  good  grounds  for  believing 
that  adequate  storage  can  render  an  initially 
impure   river  water,  relatively   (if   not  abso- 
lutely) safe  for  domestic  use.     It  is  essential, 
however,  to    render  a    stored   water  bright, 
clear,    and   palatable,    by   subsequent   filtra- 
tion. A.  C.  H. 

"  Balancing  Reservoirs."— Small  reser- 
voirs or  tanks  introduced  in  a  pipe-line 
conveying  water  with  the  object  of  reducing 
the  pressure  of  the  water  on  the  lowest  part 
of  the  pipes  by  breaking  up  the  fall  of  the 
aqueduct,  or  pipe-line  into  independent  sec- 
tions. (See  "  WATER  SUPPLY.") 


34 


BAL 


MUNICIPAL   AND    SANITAKY  ENGINEEEING. 


BAR 


Ball  Valves. — Made  use  of  to  automatic- 
ally regulate  the  supply  of  water  to  cisterns 
and  tanks,  and  for  maintaining  the  water  at 
any  given  level.  Made  in  various  patterns, 
some  to  open  vertically,  some  horizontally. 
They  all  consist  of  a  valve  acted  upon  by  a 
lever  having  a  hollow  copper  ball  at  the 
extreme  end,  which  floats  on  the  water  in  the 
cistern. 

When  the  water  sinks,  by  being  drawn  off, 
the  ball  drops  and  opens  the  valve,  or  allows 
it  to  be  opened  by  the  pressure  of  the  water  in 
the  main.  When  the  cistern  is  full  the  ball 
is  raised  and  the  lever  made  to  close  the 
valve.  The  length  of  the  lever,  and  the  size 


Ball  Valves. 


of  the  copper  ball  or  float  are  regulated  by  the 
diameter  of  the  supply  pipe  and  the  pressure 
of  water  in  the  main.  The  longer  the  lever 
and  the  larger  the  ball,  the  greater  the 
pressure  brought  to  bear  on  the  valve.  Ball 
valves  should  be  made  to  resist  from  four  to 
six  times  the  pressure  ordinarily  pressing 
against  them,  because  on  quickly  closing  a 
cock,  the  ordinary  pressure  is  considerably 
increased  by  the  shock  or  water  hammer. 
They  should  be  tested  to  act  to  their  full 
pressure  when  the  ball  is  half  immersed.  The 
valves  should  be  made  of  hard  brass  or  gun 
metal,  and  may  be  faced  or  provided  with 
leather  or  vulcanised  india-rubber  washers. 

Barometer. — People  are  not  always  con- 
scious of  the  presence  of  the  air  around  them, 
as  it  is  invisible  ;  but  they  feel  its  effects 
when  it  is  in  motion,  as  in  wind.  Air,  how- 
ever, has  weight,  which  is  equal  to  14*7  Ibs. 
to  the  square  inch.  It  is  this  weight  which 


raises  the  water  in  the  common  pump  to  the 
height  of  about  34  ft.,  this  being  prac- 
tically the  balance  of  the  weight  of  the 
atmosphere.  As  mercury  is  about  thirteen 
times  heavier  than  water,  a  column  of  about 
30  in.  of  mercury  is  held  up  in  a  tube 
which  has  been  freed  from  air,  by  the  pressure 
of  the  atmosphere,  and  such  a  column  of 
mercury  is  used  as  a  barometer,  for  showing 
the  changes  in  the  weight  of  the  atmosphere. 
The  best  form  of  barometer  is  that  of  the 
Fortin  pattern.  This  has  an  adjustable  glass 
cistern  in  order  that  the  surface  of  the  mer- 
cury therein  can  be  brought  into  contact  with 
the  ivory  point  which  forms  the  extremity  of 
the  scale.  In  the  Kew  pattern  of  barometer 
(which  is  largely  used  by  meteorological 
observers),  the  cistern  is  rigid  and  closed,  but 
the  error  arising  from  the  change  of  level  in 
the  cistern  (technically  termed  the  "  error  of 
capacity ")  is  overcome  by  contracting  the 
divisions  on  the  scale.  Every  barometer  has 
a  thermometer  fixed  to  the  brass  tube,  in  order 
to  show  the  temperature  of  the  mercury  in, 
and  the  scale  of,  the  barometer. 

The  mode  of  taking  an  observation  is  this  : — 
Eirst  note  the  reading  of  the  attached  ther- 
mometer ;  then  (if  the  barometer  is  a  Fortin) 
adjust  the  mercury  in  the  cistern  by  turning 
the  screw  at  the  bottom,  so  that  the  ivory 
point  is  just  brought  into  contact  with  the 
surface  of  the  mercury,  but  does  not  depress 
it ;  the  ivory  point  and  its  reflected  image  in 
the  mercury  should  appear  to  just  touch  each 
other  and  form  a  double  cone.  Next  adjust 
the  vernier  so  that  its  two  lower  edges  shall 
form  a  tangent  to  the  convex  surface  of  the 
mercury.  Then  read  off  on  the  scale  by 
means  of  the  vernier  to  the  thousandth  of  an 
inch.  Having  obtained  the  actual  reading  of 
the  barometer,  it  now  requires  to  be  corrected 
for  (1),  index  error,  and  (2)  temperature.  The 
correction  for  (1)  will  be  found  on  the  Kew 
certificate  if  the  barometer  has  been  verified 
at  the  Kew  Observatory.  The  correction  for 
(2),  viz.,  reducing  the  reading  to  the  standard 
temperature  of  32°  F.,  can  be  found  in  Table  I. 
of  "  Hints  to  Meteorological  Observers." 
35  D  2 


BAT 


ENCYCLOPEDIA  OF 


BAT 


The  barometer  should  be  fixed  at  such  a 
height  that  the  observer  can  read  the  vernier 
comfortably  when  standing  upright ;  it  must 
hang  vertically  and  be  in  a  good  light. 
Barometers  should  always  be  very  carefully 
handled,  so  as  to  avoid  breakage,  or  admission 
of  air  into  the  tube.  It  is  best  to  carry  the 
instrument  with  the  cistern  end  upwards.  In 
the  case  of  a  Fortin  barometer,  the  mercury 
should  be  screwed  up  so  as  to  fill  the  tube  and 
cistern  before  the  instrument  is  taken  down. 

Another  form  of  barometer  is  the  aneroid. 
This  is  an  instrument  consisting  essentially  of 
an  elastic  metal  box,  exhausted  of  air,  which 
indicates  on  a  dial  the  changes  due  to  varia- 
tions of  external  pressure  on  the  box,  and 
therefore,  acting  as  a  barometer.  Aneroids 
are  very  handy  and  useful  instruments ;  they, 
however,  should  not  be  absolutely  relied  upon 
for  long  periods,  but  should  be  checked  from 
time  to  time  against  a  mercurial  barometer. 

A  self-recording  aneroid  or  barograph  is  an 
interesting  instrument,  as  it  yields  a  con- 
tinuous record  of  the  variations  of  atmo- 
spheric pressure.  As  the  pressure  of  the 
atmosphere  diminishes  according  to  altitude, 
the  barometer  is  often  used  for  the  measure- 
ment of  heights.  In  comparing  barometric 
observations  made  at  different  places,  account 
must  be  taken  of  their  respective  heights 
above  sea-level ;  for  the  higher  the  station, 
the  lower  will  be  the  reading  of  the  barometer. 
So  for  the  preparation  of  isobaric  maps  it  is 
necessary  to  reduce  all  the  readings  to  sea- 
level.  Tables  for  this  purpose  will  be  found 
in  the  "Hints"  referred  to  above.  W.  M. 

Baths  for  domestic  purposes  are  made  in  a 
variety  of  shapes  and  sizes  to  suit  special 
requirements.  The  normal  dimensions  of 
"  full-size  "  baths  are : — 

ft.  in. 

Length  .  .  .  .  .56 
Breadth  at  head  .  .  .21 
Breadth  at  foot  .  .  .18 

Depth 1  10 

These  dimensions  are  all  internal.  It  is  usual 
for     baths    to    taper    from    head     to     foot 


36 


and  from  top  to  bottom  to  economise 
water.  When  the  users  are  above  average 
size  or  stout,  "parallel  side  "baths  should 
be  made  use  of  as  allowing  more  room. 
Baths  are  made  of  various  materials,  such  as 
zinc,  copper,  cast-iron,  fire-clay,  marble,  and 
steel.  Zinc  baths  are  not  durable.  They 
were  formerly  much  used  for  cheapness,  but 
cast-iron  baths  are  now  made  equally  inex- 
pensive, and  prove  much  more  satisfactory, 
and  have  therefore  almost  entirely  superseded 
them.  Copper  baths  are  also  out  of  date, 
mainly  by  reason  that  they  have  to  be  fixed 
in  cradles  and  enclosed  in  wood  to  prevent 
them  from  losing  their  shape.  They  have  the 
advantage  that  they  do  not  absorb  much  heat 
from  the  water.  "  Porcelain  "  or  fire-clay 
baths  are  not  now  so  frequently  used  as 
formerly.  They  are  heavy,  cold  to  the  touch, 
comparatively  expensive,  and  very  liable  to 
fracture.  Much  the  same  remarks  apply  to 
marble  baths,  which  may  be  cut  from  the 
solid  block  or  made  up  of  slabs.  The  more 
generally  useful  and  satisfactory  baths  are 
made  of  cast-iron,  porcelain,  or  vitreous 
enamelled.  The  former  are  the  better,  but 
the  latter  are  slightly  cheaper.  Porcelain 
enamelled  steel  baths  stamped  from  the  sheet 
are  of  recent  introduction.  They  promise  to 
combine  the  advantages  of  the  iron  baths  with 
cheapness  and  light  weight,  but  have  not  at 
present  had  a  sufficiently  long  trial  to  warrant 
a  judgment  as  to  their  durability.  All  baths 
should  be  fixed  without  enclosures. 

Baths,    Open- Air.  —  Site — Accommodation 
—  The    Swimming   Tank  —  Entrance   Lodge  — 
Dressing  Boxes. 

SITE. — This  should  be  preferably  in  a  public 
park  or  in  some  open  spot.  The  land  should 
be  fairly  level,  and  lend  itself  to  enclosure 
without  being  unsightly.  If  the  site  is  sur- 
rounded by  a  belt  of  trees  so  much  the  better. 

ACCOMMODATION. — After  settling  upon  the 
site,  the  next  point  will  be  the  accommodation 
required.  This  is  generally  as  follows  :— 
Swimming  bath,  entrance  lodge,  conveniences, 
dressing  boxes  or  sheds,  slipper  and  shower 


BAT 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


BAT 


baths  (sometimes).  As  the  "  open-air  treat- 
ment "  is  the  main  feature  of  this  type  of  bath, 
slipper  baths  are  very  rarely  required. 

THE  SWIMMING  TANK. — This  may  be  either 
sunk  in  the  ground  or  built  on  the  ground. 
The  more  convenient  way  seems  to  be  the 
former.  The  size  must  be  decided  upon  accord- 
ing to  the  number  of  bathers  expected.  The 
depth  should  be  from  about  5  ft.  at  the  shallow 
end  to  10  ft.  at  the  deep  end,  the  water-line  being 
1  ft.  below  the  top  of  the  coping  round  the 
bath  edge.  The  walls  will  be  constructed  of 
concrete,  either  reinforced  or  ordinary  concrete 
construction.  A  rough  method  of  calculating 
the  thickness  of  the  wall  is  as  follows : — 

Thickness  at  top  of  wall  =  height  X  '30 

,,         ,,    middle  of  wall  =   ,,     X  "50 

„   bottom,,    ,,     =    „     X  '70 

This  is  only  approximate,  but  is  on  the  safe 
side.  To  get  the  accurate  thickness  of  wall, 
diagrams  of  the  thrust  must  be  drawn. 

The  walls  should  be  constructed  in  two 
thicknesses,  the  outer  portion  having  wall  ties 
embedded  every  yard — one  to  every  yard 
super  of  wall  face.  Over  this  face  is  put  the 
bitumen  sheeting  for  making  the  tank  water- 
tight; and  the  inner  wall — about  6  in.  in 
thickness — is  then  constructed,  being  held  to 
the  outer  portion  by  the  wall  ties. 

The  floor  is  constructed  in  a  similar  manner, 
i.e.,  in  two  thicknesses,  having  bitumen 
between  the  layers,  which  should  not  be  less 
than  4^  in.  in  thickness.  The  top  layer  of 
the  concrete  floor  should  be  constructed  in 
alternate  squares,  about  6  ft.  sides  to  allow  of 
uniform  shrinkage. 

A  handrail  should  be  fixed  round  the  inside 
of  the  bath,  1  ft.  from  the  top  of  the  coping. 

The  coping  should  not  hang  over  the  edge 
of  the  bath  more  than  2  in. 

Gangways  round  the  bath  should  be  wide 
and  paved  with  either  stone  or  granolithic, 
falling  away  from  the  edge  of  the  bath  to  a 
channel. 

Diving-stages,  platforms,  and  water-shutes 
should  be  provided.  Oiled  teak  will  be  found 
the  most  serviceable  for  the  diving  stages. 


The  steps  of  the  stage  should  be  covered  with 
indiarubber  to  give  a  firm  foothold. 

Steps  should  be  provided  leading  into  the 
bath  at  each  corner,  either  of  stone  or  teak. 


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37 


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ENCYCLOPEDIA   OF 


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If  of  teak,  lead  should  be  fastened  to  the 
bottom  step  to  keep  same  from  floating. 

ENTRANCE  LODGE. — This  should  contain 
room  for  the  attendant  and  pay  office.  Con- 
veniences may  be  placed  at  each  side  of  the 
entrance,  having  entrances  both  from  the 
inside  of  the  bath  enclosure  and  from  the 
outside,  so  that  when  the  bath  is  not  in  use 
the  conveniences  may  be  used  by  the  outside 
public.  Accommodation  should  be  provided 
for  both  sexes. 

DRESSING  BOXES  OR  SHEDS. — These  should 
be  placed  either  round  each  side  or  along  one 
or  more  sides.  They  may  be  either  separate 
dressing  boxes  or  one  long  shed  with  seating 
accommodation,  and  hooks  for  clothes. 

It  will  be  found  possible  to  use  the  earth 
excavated  from  the  bath  tank  as  a  screen 
round  the  bath  by  forming  an  embankment. 

The  dressing  boxes  or  sheds  may  then  be 
either  on  one  or  any  of  the  sides. 

If.  any  open  shed  is  provided,  provision 
should  be  made  for  temporary  division  into 
compartments  when  it  is  women's  day. 
Curtains  will  be  found  sufficient  for  this. 

(For  Acts  of  Parliament,  see  below.)     R.H.B. 

Baths,  Public  Swimming  and  Slipper. 

— Acts  of  Parliament — General  Considerations — 
Swimming  Hall — Bath — Corridors — Gallery- 
Diving  Platform — Attendant's  Cabins — Water 
Shute  —  Entrances  —  Club  Room  —  Pay  Box — 
Ventilation  and  Warming  —  Slipper  Baths  — 
Superintendent's  Apartments  —  Establishment 
Laundry— Boiler  House — Temporary  Floor — 
Continuous  Filtration. 

ACTS  OF  PARLIAMENT. — The  Acts  of  Parlia- 
ment governing  the  provision  of  Public  Baths 
commenced  with  the  Bath  and  Wash-houses 
Act,  1846,  which  is  an  adoptive  Act.  This 
Act  entitles  public  Authorities  to  erect  suitable 
buildings  for  public  baths  and  wash-houses, 
and  also  make  open  bathing  places,  and  con- 
vert any  building  for  the  same  use.  After 
seven  years'  use  the  public  authority  may  sell 
the  buildings  and  land,  if  they  should  find 
that  their  working  is  too  expensive.  An  im- 
portant section  is  that  which  provides  that  a 


copy  of  the  Bye-Laws  made  in  respect  of  this 
Act  shall  be  hung  in  every  bath-room. 
Section  36  provides  that  the  number  of  baths 
for  the  working  classes  shall  not  be  less  than 
twice  the  number  of  the  baths  of  any  higher 
class  if  but  one,  or  of  all  the  baths  of  any 
higher  class  if  more  than  one,  in  the  same 
building.  Schedule  B  relates  to  the  scale  of 
charges,  but  was  subsequently  repealed  and 
amended.  The  Act  was  amended  in  1847, 
extending  its  power  to  further  authorities 
and  also  regulating  the  number  of  first-  and 
second-class  washing  troughs  on  the  same 
basis  as  the  slipper  baths  referred  to  in 
section  36  of  the  first  Act.  The  amended  Act 
of  1847  contains  a  revised  list  of  charges  for 
the  use  of  the  baths.  The  Act  was  again 
amended  in  1878  to  allow  the  bathing  places 
mentioned  as  being  "  open  "  in  the  1846  Act 
to  be  roofed  over.  The  Act  also  limits  the 
period  during  which  a  swimming  bath  may  be 
closed  to  an  extent  of  five  months  in  any  one 
year  beginning  with  November  and  termi- 
nating at  March.  The  local  authority  may 
during  that  time  use  it  as  a  gymnasium  or 
place  of  recreation,  or  for  parochial  meetings, 
but  not  for  music  or  dancing.  The  Act  also 
contains  a  list  of  charges  relating  to  covered 
swimming  baths.  In  1882  the  Act  was  once 
more  amended  in  order  to  allow  of  baths,  &c., 
being  erected  outside  the  parish  but  within 
easy  distance  of  same.  The  amendment  of 
1896  repealed  section  5  of  the  Act  of  1878 
which  debarred  the  use  of  the  bath  during  the 
winter  season  for  the  purposes  of  music  and 
dancing,  but  only  so  far  as  London  was  con- 
cerned, and  then  only  after  an  applica- 
tion made  to  the  London  County  Council. 
However,  in  the  year  1899  section  5  in  the 
Act  of  1878,  which  was  still  in  force  every- 
where except  in  London,  and  which  prevented 
the  use  of  the  building  for  music  and  dancing, 
was  repealed,  and  the  buildings  could  thence- 
forth be  used  for  that  purpose,  subject  to 
permission  being  obtained  from  the  County 
Council  of  their  several  districts. 

GENERAL  CONSIDERATION  OF  THE  SUBJECT. — 
When    considering    the   question    of    public 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


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baths,  there  are  several  views  which  might  be 
entertained,  namely,  whether  it  is  more  desir- 
able to  group  the  swimming  baths,  slipper 
baths,  and  wash-houses  in  one  centre,  than  to 
build  say,  a  swimming  bath  in  one  spot, 
generally  accessible  to  the  whole  town,  and  to 
erect  one  or  more  buildings  containing  slipper 
baths  in  other  parts,  preferably  congested 
areas.  The  status  of  the  town  would  likewise 
determine  whether  there  should  be  a  first-  and 


be  free.  Again  the  size  and  character  of  the 
baths  will  be  determined  by  the  conditions  of 
the  neighbourhood.  In  some  places  there  will 
be  a  greater  demand  for  a  first-class  swimming 
bath.  In  another  there  may  be  a  preponder- 
ance of  school  children  which  will  require 
more  attention  being  paid  to  baths  for 
their  accommodation.  A  wash-house  or 
public  laundry  will  be  much  in  demand  in  a 
poor  neighbourhood,  and  as  such,  should 


FIG.  1. — Temporary  Floor  for  Public  Swimming  Bath.     Designed  by  E.  J.  Angel,  A.E.I.B.A. 


second-class  bath  and  also  a  separate  bath 
for  women,  or  whether  it  would  be  more 
economical  to  set  apart  a  certain  day  when 
the  first-  or  second-class  baths  could  be 
reserved  for  women.  There  is  often  an 
objection  on  the  part  of  women  to  the  latter 
arrangement,  as  it  is  frequently  inconvenient 
for  persons  to  so  regulate  their  appointments 
that  a  swim  if  desired  must  be  taken  on  a 
certain  day  and  at  a  particular  hour,  while 
the  men  on  the  other  hand  object  to  being 
closed  out  on  perhaps  the  only  day  of  the 
week  when  their  business  will  allow  them  to 


receive  a  considerable  amount  of  attention, 
but  its  entrance  and  general  position  should 
be  kept  as  far  away  as  possible  from  the  other 
portions  of  the  building,  and  provision  be 
made  for  the  sundry  perambulators,  mail 
carts,  &c.,  used  by  the  customers  for  the 
transit  of  their  laundry  work.  The  shape  and 
position  of  the  site  are  important  matters, 
both  with  regard  to  the  initial  cost,  subsequent 
up-keep,  and  convenience  of  administration. 
A  long  narrow  site  will  necessitate  long 
corridors,  costly  in  their  design,  awkward  for 
the  public  and  difficult  in  supervision. 
39 


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THE  SWIMMING  HALL. — The  internal  faces 
of  the  walls  should  be  of  red  pressed  bricks  as 
they  are  not  liable  to  condensation  and  a 
glazed  brick  dado  shoulder  high  should  be 
provided.  Some  slight  attempt  at  architec- 
tural treatment  might  be  indulged  in  by 
forming  pilasters  under  the  roof-trusses  with 
string  courses  and  ornamental  bands,  and  seg- 
mental  arches  or  oversailing  courses  at  the 
eaves.  It  is  not  advisable  to  construct  any 
windows  which  will  admit  direct  sunlight, 
particularly  on  to  the  water  as  it  not  only 
annoys  the  bathers  but  promotes  vegetable 
growth  within  the  bath.  The  roof -truss  should 
be  of  iron,  and  its  design  is  a  matter  for  the 
architect  to  decide.  Some  roofs  are  sloped  to 
an  ordinary  pitch,  with  either  a  flat  or  curved 
tie  rod,  and  boarded  on  the  underside  with 
diagonal  boarding  and  the  usual  lantern  lights 
along  the  apex;  while  other  roofs  of  successful 
design  have  been  formed  of  segmental  section 
with  curved  lattice  principals.  It  is  usual  to 
form  the  sides  of  the  lantern  with  fixed  wooden 
louvre  boards  for  natural  ventilation,  but  if 
the  bath  is  to  be  ventilated  in  such  a  manner  as 
to  free  the  entrance  doors  as  much  as  possible 
from  draughts  and  an  in-rush  of  cold  air,  the 
plenum  system  seems  to  be  the  one  best 
adapted.  In  that  case  there  should,  of  course, 
be  no  open  louvres  in  the  roof.  All  glass  in 
the  roof  should  be  wired  with  netting  within 
the  thickness  of  the  glass.  The  artificial 
lights,  whether  gas  or  electric,  are  best  kept 
away  from  the  centre  of  the  pond,  and  placed 
so  as  to  be  accessible  from  the  gangway.  The 
swimming  bath  is  generally  the  one  item 
which  determines  the  whole  plan,  and  is  the 
making  or  marring  of  the  scheme.  The 
swimming  bath  should  be  so  planned  that  it 
may  be  most  convenient  not  only  for  its  obvi- 
ous intention,  namely,  a  bath  to  swim  in,  but 
also  a  bath  in  which  competitions  may  take 
place  and  be  viewed  by  the  public,  and  in 
addition  to  this  be  used  during  the  winter 
season  as  a  public  hall.  In  order  to  be  used 
for  the  two  latter  purposes,  convenient 
entrances,  exits  and  emergency  exits,  both 
from  the  gallery  and  floor  level,  should  be 


provided,  together  with  facilities  for  receipt  of 
entrance  fees. 

THE  BATH. — The  best  manner  to  form  the 
excavation  is  to  dig  out  for  the  exact  size  of 
the  boundary  walls  of  the  bathing  hall,  carry- 
ing the  footings  of  the  walls  down  to  the  level 
of  the  bottom  of  the  bath,  utilising  the  inter- 
vening space  between  the  wall  and  the  bath 
for  laying  the  pipes  and  allowing  sufficient 
room  for  workmen  to  execute  repairs.  The 
length  of  the  bath  along  the  waterline,  should, 
for  racing  purposes,  be  a  fraction  of  a  mile, 
thus  105  ft.  7  in.  equals  one  fiftieth  of  a  mile 
and  this  is  for  all  purposes  a  convenient 
length,  although  some  are  made  132  ft.  or  one 
fortieth  of  a  mile.  A  short  or  an  odd  length 
will  be  sure  to  produce  dissatisfaction  among 
expert  swimmers.  The  width  should  not  be 
great,  no  advantage  being  obtained  by  making 
it  anything  over  30  or  36  .ft.  wide  (numbers 
dividable  into  yards).  It  should  be  remem- 
bered that  an  increase  of  width  means  a  larger 
proportion  of  expenditure  in  construction  than 
would  be  the  case  with  an  increase  in  length, 
as  heavier  scantling  is  required  for  the  roof, 
and  more  material  both  in  roof  covering  and 
bath  construction,  both  of  which  are  expensive 
items.  The  depth  of  the  water  should  vary 
from  3  ft.  6  in.  to  6  ft.  6  in.,  and  the  bottom 
slope  of  the  bath  should  run  in  an  even  gradi- 
ent from  the  shallow  end  to  about  10  ft.  from 
the  deep  end,  the  latter  10  ft.  having  just 
enough  slope  to  drain  itself.  Ladies'  baths, 
however,  should  be  about  50  ft.  long  by  25  ft. 
wide,  and  with  3  ft.  6  in.  to  5  ft.  6  in.  depth  of 
water.  The  floor  of  the  bath  should  be  formed 
of  concrete  of  an  even  thickness  of  not  less 
than  2  ft.  It  is  advisable  to  form  the  excava- 
tion to  the  same  slope  as  the  bath  floor,  not 
as  is  sometimes  done  by  stepping  the  excava- 
tion in  level  sections  and  forming  the  top 
surface  of  the  concrete  on  the  slope.  This 
method  will  exhibit  a  weak  spot  where  one 
step  joins  another  and  tends  to  produce  a 
crack  due  to  the  unequal  contraction  and 
expansion  of  the  material.  It  is,  however, 
advisable  to  roughen  the  surface  of  the  excava- 
tion to  avoid  any  tendency  of  the  concrete  to 


40 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


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"  creep."  The  concrete  bottom  should  be 
carried  under  the  sides  of  the  bath  and  pro- 
ject on  the  outside  for  at  least  a  foot.  The 
sides  of  the  bath  should  for  preference  be  of 
concrete  ramped  or  stepped  in  varying  thick- 


asphalte  should  be  about  an  inch  thick  laid  in 
two  thicknesses  and  of >•  such  a  consistency  that 
it  will  not  run  when  the  temperature  of  the 
water  is  raised.  The  interior  of  the  bath  is 
lined  with  4J  in.  white  glazed  bricks  on  the 


FlG.  2. — Temporary  Floor  for  Public  Swimming  Bath.     Designed  by  E.  J.  Angel,  A.E.I.B.A. 


nesses  from  4  ft.  at  the  base  to  18  in.  at  the 
top.  Buttresses  at  intervals!  should  not  be 
built,  but  the  wall  should  be  constructed  of 
continuous  thickness,  each  diminution  of 
thickness  being  perfectly  horizontal.  The 
inside  face  of  the  concrete  should  be  left 
rough  to  provide  for  a  layer  of  asphalte  being 
put  as  a  waterproof  covering  over  all.  This 


sides,  varied  sometimes  with  a  coloured  (green) 
band  along  the  top  courses.  It  is  not  neces- 
sary to  tie  this  4£  in.  lining  into  the  main 
body  of  the  work.  The  bottom  of  the  bath 
may  be  either  "  brick  flat,"  brick-on-edge,  or 
thick  tiles,  the  whole  very  carefully  jointed 
with  Portland  cement  compo.  It  is  advisable 
to  fill  the  bath  with  water  after  the  asphalte 


41 


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has  been  finished  and  before  the  brick  lining 
has  been  commenced  so  as  to  test  for  water 
leakage.  It  is,  of  course,  assumed  that  the 
earth  forming  the  foundation  of  the  bath  is 
firm  and  secure,  any  defective  portion  being 
dug  out  and  the  hole  filled  with  concrete. 
There  is  no  advantage  to  be  obtained  in  using 
reinforced  concrete  in  either  walls  or  bed,  as 
it  does  not  need  so  much  as  a  "  collapse  "  to 
destroy  the  utility  of  the  work,  a  simple  crack 
or  fissure  being  quite  sufficient  to  ruin  the 
watertightness  of  the  bath,  and  this  is  just  as 
likely  to  occur  with  reinforced  work  as  with- 
out it.  Especial  care  must  be  taken  in  build- 
ing-in  all  connections  to  pipes.  It  is  as  well 
to  have  a  double  flange  to  such  connections, 
one  placed  on  the  inside  of  the  bath  and  the 
other  outside,  and  packing  the  concrete  in 
between.  All  such  connecting  pieces  should 
be  built  in  as  the  concrete  is  laid.  Overflows 
and  scum  troughs  should  be  formed  on  the 
sides  and  more  particularly  at  the  deep  end  ; 
and  also  places  where  bathers  can  spit, 
although  in  some  of  the  newer  baths  this 
latter  has  been  omitted,  but  whether  provided 
or  omitted  the  tendency  to  spit  exists  so  that 
it  is  better  to  provide  for  it  than  to  allow 
bathers  to  expectorate  in  the  water  or  on  to 
the  gangway.  A  handrail  of  galvanized  iron 
tubing  about  2J  in.  diameter  should  be  placed 
about  2  in.  clear  of  the  water.  The  top  of  the 
gangway  should  be  about  15  in.  above  the 
water  line.  It  is  assumed  that  there  will  be  a 
passage  formed  around  the  walls  of  the  tank 
itself  for  pipes,  &c.,  so  that  the  floor  or  gang- 
way around  the  tank  will  form  the  ceiling  or 
covering  to  it.  This  gangway  should  be  of 
steel  girders  in  concrete  and  covered  with 
some  non-absorbent  and  non-slippery  paving 
material.  York  flags  and  slate  have  been 
used,  but  both  these  are  undesirable  ;  certain 
qualities  of  red  tiles  are  better,  and  one  bath 
in  London  has  a  flooring  of  rubber  tiles,  but 
this  has  a  tendency  to  allow  water  to  percolate 
between  the  joints.  Great  importance  must 
be  paid  to  the  non-slipperyness  of  the  paving 
material.  The  curb  around  the  bath  may  be  a 
4  in.  finely  tooled  or  rubbed  York  stone  with 


a   round   nosing.     This   gangway   should   be 
from  4  ft.  to  4  ft.  6  in.  wide,  and  if  chairs  are 
to  be  placed  along  the  gangway  during  enter- 
tainments it  should  be  5  ft.  wide.     Consider- 
able space  should  be  allowed  at  either  end  as 
it   is   there  people  mostly  congregate — there 
should  certainly  be  a  not  less  space  than  12  ft. 
at  the  deep  end  as  races  generally  start  from 
here  and  the  opposite  end  may  be  6  or  8  ft. 
wide.     The   gangways   should   have   a   slope 
from  the  water's  edge  towards  the  dressing 
boxes,  and  a  shallow  channel  be  formed  next 
to  the  boxes,  with  trapped  galvanized  gullies  at 
intervals.     The  dressing  boxes  should  only  be 
ranged  along  the  long  sides  of  the  bath  and 
should   be   raised   above   the   gangway  by  a 
2£  in.  to  3  in.  step.     The  floor  of  the  dressing 
boxes  should  be  of  maple  as  this  is  the  best 
wood  to  use  where  the  floor  is  constantly  wet. 
The  size  of  the  boxes  ought  not  to  be  less 
than  3  ft.  6  in.  by  3  ft.  6  in.  for  the  first-class 
baths  and  3  ft.  by  2  ft.  9  in.  for  the  second- 
class.    The  framing  should  be  of  pitch  pine  or 
teak,  framed  with  as  few  internal  angles  as 
possible,   of   light  scantling  compatible  with 
strength,  and  filled  in  with  panels  in  prefer- 
ence to  either  beaded  or  V- jointed  boarding. 
The  door  should  be  about  4  ft.  6  in.  high  and 
in  the  case  of  the  women's  bath  there  should 
be  a  rail  and  curtain  provided  to  fill  up  the 
space  to  the  top  of  the  box.     The  width  of  the 
doors  need  not  be  more  than  27  in.  and  the 
remaining  portion  of  the  front  may  be  carried 
up  to  the  top  of  the  box.     In  some  of  the 
more  recent  baths  the  door  is  also  carried  up 
for  the  full  height,  but  the  upper  panels  are  in 
the  form  of  a  grill.     In  the  latter  case  the 
latch  which  is  provided  should  be  opened  on 
the  inside  with  a  knob  and  on  the  outside  by 
an  attendant's  key.     The  door,  and  sometimes 
the  framed  divisions,  are  kept  off  the  ground 
about  3  or  4  in.,  but  the  latter  in  some  locali- 
ties is   open  to  objection  as  it  leads  to  the 
temptation  for  articles,  such  as  boots,  clothing, 
&c.,  which  may  be  on  the  floor  being  stolen 
by   persons   in   the   adjoining   box.     In   the 
public  baths  at  Camberwell  and  Hoxton  the 
framing  is  made  collapsible  and  folds  back 
42 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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against  the  wall,  the  seat  also  being  .hinged, 
allowing  of  a  considerable  area  being  thrown 
into  the  hall  for  public  meetings.  A  fixed 
seat  (capable  of  being  unscrewed),  a  slatted 
footboard,  two  hooks,  and  a  mirror  complete 
the  furnishing  of  the  dressing  box.  No  steel 
or  ironwork  should  be  used  for  the  fittings, 
even  the  butt  hinges  on  the  doors  should  be 
of  brass,  so  as  to  dispense  with  liability  to 
rust.  The  feet  of  the  uprights  should  be  let 
into  galvanized  sockets  set  in  the  concrete 
floor  to  protect  the  wood  from  damp.  There 
should  be  two  w.c.'s  and  urinals  for  each 
class  of  bath,  and  it  is  advisable  that  they 
should  be  in  a  compartment  leading  off  the 
main  hall.  A  foot  bath  about  18  in.  deep 
should  also  be  provided  somewhere  near 
the  entrance  so  as  to  be  under  the  control 
of  the  attendant  and  supplied  with  warm 
water,  its  size  being  about  4  ft.  by  3  ft.  and 
have  an  outlet  for  the  rapid  discharge  of 
water.  A  wooden  seat  should  be  ranged 
around  three  sides  where  several  bathers  may 
sit  together  and  cleanse  their  feet  before 
entering  the  bath.  This  is  especially  useful 
where  schools  attend  the  baths.  A  shower 
bath,  if  provided,  should  be  separated  from 
the  foot  bath,  it  can  then  be  used  indepen- 
dently and  need  only  be  sufficiently  large  for 
one  person  to  stand  in.  Most  public  baths 
are  now  provided  in  either  the  first-  or  second- 
class  divisions  with  a  gallery  for  the  public  to 
view  entertainments.  This  is  mostly  done  in 
the  first-class  bath.  The  gallery  should  comply 
with  the  local  regulations  with  respect  to  safety 
of  places  of  public  entertainment.  The  regu- 
lations in  force  in  London  are  mostly  followed 
by  the  provincial  towns  and  are  set  forth  in 
an  amended  form  dated  13th  November, 
1906,  arid  entitled  "  Regulations  made  by  the 
(London  County)  Council  with  respect  to  the 
requirements  for  the  protection  from  fire  of 
theatres,  houses,  rooms,  and  other  places  of 
Public  resort  within  the  Administrative  County 
of  London."  The  chief  points  affecting  public 
baths  when  used  for  entertainments  are 
that  each  gallery  accommodating  not  more 
than  300  persons  must  have  two  exits  each 


4  ft.  wide.  There  shall  be  no  recesses  along 
the  walls  within  5  ft.  from  the  floor ;  all  stair- 
cases must  be  of  stone  or  other  incombustible 
material  and  4  ft.  wide,  with  steps  having 
11  in.  treads  and  6  in.  risers  with  no  winders, 
and  not  less  than  three  steps  in  a  flight  or 
more  than  fifteen  without  an  intervening 
landing.  All  doors  shall  open  away  from  per- 
sons leaving  the  hall  and  have  panic  bolts 
fitted  and  be  hung  in  two  leaves.  Swing 
doors  for  the  interior  are  preferable.  All 
doors  leading  out  to  be  properly  marked  with 
the  word  EXIT. 

COKRIDOKS  AND  PASSAGES. — The  corridors  and 
passages  throughout  the  building  are  best  lined 
with  glazed  bricks,  and  the  floors  covered  with 
Terazzo  or  Mosaic  tiles,  as  they  are  easily 
cleaned. 

GALLERY. — The  design  of  the  gallery  should 
'  be  such  that  the  water  may  be  seen  for  its  full 
width  by  all  persons  when  seated.  This  will 
probably  mean  that  the  steps  carrying  the 
seats  must  be  fairly  steep.  There  should  be 
nothing  movable,  and  all  timbers,  especially 
the  gallery  front,  should  be  extra  strong  to 
provide  against  danger  arising  from  the  public 
pressing  forward.  There  should  be  no  means 
of  communication  between  the  body  of  the 
hall  and  the  gallery,  which  should  have  its 
own  separate  entrance  and  emergency  exits. 
The  gallery  could  very  well  be  carried  around 
each  of  the  four  sides  of  the  hall,  supported 
over  the  boxes  by  thin  columns  designed  to 
coincide  with  the  divisions  between  the  com- 
partments, but  at  either  end  of  the  bath, 
where  there  are  no  boxes,  the  columns  should 
be  omitted  and  cantilevers  used. 

DIVING  PLATFORM. — A  diving  stage  is  pro- 
vided at  the  deep  end  of  the  bath  in  the  form 
of  three  steps,  the  bottom  step  being  about 
2  ft.,  the  next  4  ft.,  and  the  top  6  ft.  above  the 
gangway  level.  Sometimes  there  is  only  the 
one  provided,  at  a  height  of  about  2  ft.  6  in., 
and  this  as  long  as  possible. 

ATTENDANT'S  CABINS. — A  cabin  for  the  atten- 
dant, stores  for  used  towels  (or  a  shute  for 
same  to  the  basement),  should  be  provided, 
and  also  accommodation  for  brushes,  buckets, 


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&c.,  &c.      These   compartments  are  usually     of  the  large  hathing  hall  is  a  matter  which 


near  the  entrance. 

WATER- SHUTE. — A  shute  is  also  a  useful 
adjunct  to  the  bath,  formed  of  teak  24  in.  wide 
by  3  in.  thick,  with  sides  projecting  3  in.  above 
the  surface.  The  shute  is  hung  on  rods  from 
the  roof  principals,  a  spray  is  fixed  along  rhe 
top  end,  and  the  shute  is  reached  by  a  fixed 
ladder. 

ENTRANCES. — The  entrance  to  each  of  the 
bathing  halls  should  be  through  a  short  vesti- 
bule having  folding  doors  at  each  end  so  as  to 
cut  off  all  draughts,  and  screen  the  hall  from 
observation.  The  entrance  is  generally  at 
the  deep  end  of  the  bath. 

CLUB  EOOM. — In  baths  of  any  distinction, 
there  should  be  a  room  for  the  use  of  clubs 
and  committees,  designed  so  as  to  be  acces- 
sible both  from  the  bathing  hall  and  also  from 
the  corridor  outside.  Also  an  artistes'  room 
may  be  provided  somewhere  near  the  deep  end 
of  the  bath. 

PAY  Box. — The  pay  box  is  generally  at  the 
front  of  the  building,  and  so  placed  as  to  divide 
the  first  from  the  second-class  entrances,  each 
entrance  serving  both  the  swimming  and 
slipper  baths  in  their  respective  class.  It  is 
advisable  to  provide  a  separate  pay  box  for 
the  women's  slipper  baths  (and  also  for  their 
swimming  baths  if  one  is  provided).  Their 
entrance  should  not  be  through  the  same  door 
as  the  men  except  on  days  when  the  women 
use  either  the  first-  or  second-class  swims,  in 
the  absence  of  a  special  bath  being  provided. 
If  properly  designed,  the  men  using  the 
slipper  baths  and  the  women  passing  into  the 
swimming  bath  on  their  special  day  will  be 
effectually  separated.  It  is  as  well  to  so  place 
the  first-  and  second-class  swimming  baths 
that  they  should  be  divided  with  the  same 
division  wall ;  this  will  economise  the  piping 
and  simplify  the  construction,  and  as  a  door 
of  communication  could  be  provided  it  will 
be  found  very  useful  on  gala  nights,  to  swim 
off  the  first  heats  of  a  race  in  the  otherwise 
vacant  bath,  while  the  entertainment  is  pro- 
gressing in  the  other. 

VENTILATION  AND  WARMING. — The  ventilation 


44 


should  receive  keen  attention.  Unless  great 
care  is  exercised  draughts  will  ensue,  or  else 
an  unpleasant  steamy  odour  will  exist,  especi- 
ally when  large  numbers  of  bathers  are  using 
the  water.  When  schools  are  bathing  this 
smell  is  very  evident.  To  efficiently  ventilate 
so  large  a  hall  when  used  either  for  bathing 
purposes  or  public  meetings,  it  is  quite  useless 
to  depend  on  natural  ventilation.  On  the 
one  hand,  the  air  may  be  exhausted  by  an 
electric  or  water-power  fan  (the  water  being 
used  either  for  flushing  or  in  the  bath),  placed 
in  the  roof  and  dry  warm  air  admitted  by 
Tobin's  tubes,  placed  6  ft.  above  the  floor,  or 
the  Plenum  system  could  be  adopted,  whereby 
dry,  warm  air  could  be  admitted  at  the  eaves 
line  of  the  roof,  and  expelled  through  aper- 
tures near  the  base  of  the  wall,  which  are 
connected  continuously  to  ducts  passing 
through  the  subway.  There  are  advantages 
and  objections  to  both  systems.  In  the  first, 
the  distribution  of  the  fresh  air  may  be  un- 
equal and  unpleasantly  severe  in  the  neigh- 
bourhood of  the  inlet,  and  cause  an  inrush  of 
cold  air  at  the  entrances  each  time  the  doors  are 
opened,  while  in  the  second  instance,  vermin 
may  get  into  the  duct,  especially  at  baths 
where  large  numbers  of  lower  class  school 
children  bathe.  Mr.  Aldwinkle,  F.R.I.B.A., 
has  overcome  the  objection  of  the  large  amount 
of  cold  air  which  accumulates  in  the  upper 
part  of  the  roof  of  the  hall,  by  discharging 
warmed  air  above  the  line  of  the  eaves,  on 
the  Plenum  system.  Hot  water  pipes  on  the 
low  pressure  system  are  frequently  laid  along 
the  sides  of  the  hall,  behind  the  dressing 
boxes — useful  on  occasion  of  public  meetings, 
and  also  at  certain  times  of  the  year  when 
the  hall  is  uncomfortably  chill  to  bathers. 

WAITING  ROOM. — Adjoining  the  entrances 
there  should  be  a  waiting  room  for  each  sex 
and  each  class  of  bathers,  awaiting  their  turn 
to  use  the  slipper  baths.  The  slipper  baths 
should  be  accessible  immediately  out  of  this 
room,  and  long  corridors  avoided. 

SLIPPER  BATHS. — It  is  necessary  when  pre- 
paring the  design  to  recollect  that  portion  of 


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the  Act  which  requires  twice  the  number  of 
second-class  baths  to  be  provided  as  there  are 
in  the  first-class.  The  size  of  a  slipper  bath- 
room is  about  6  ft.  wide  by  6  ft.  6  in.  long. 
The  baths  are  placed  in  pairs  on  either  side 
of  the  dividing  partition.  It  is  best  to  design 
the  arrangement,  if  it  is  possible,  so  that  the 
room  containing  the  slipper  baths  may  be 
about  17  ft.  wide,  and  have  windows  on  each 
side.  This  will  allow  a  row  of  bath-rooms  to 
be  erected  along  each  outer  wall,  lit  by  direct 
daylight,  and  separated  by  a  central  corridor 
4  ft.  wide.  The  flooring  may  be  of  concrete, 
granolithic  or  mosaic.  The  partitions  are 
generally  6  ft.  6  in.  high  and  1  in.  thick.  It  is 
not  advisable  for  the  division  to  be  fixed  so  as 
to  leave  a  space  at  the  floor  line.  Articles  of 
clothing  may  drop  and  get  kicked  into  the 
next  compartment,  or  be  stolen.  The  space 
causes  a  considerable  draught,  and  there  is 
not  that  idea  of  privacy  which  is  desired. 
Moreover,  in  washing  one  bath,  the  adjoining 
one  gets  wet.  Enamelled  slate  is  the  best 
material  for  both  division  and  door.  Marble 
looks  much  better  but  is  more  costly,  and  is 
very  liable  to  fracture  along  the  veins.  If  the 
doors,  which  should  be  about  27  in.  wide,  are 
made  about  a  J  in.  less  in  width  than  the 
opening,  there  will  be  no  fear  of  their  break- 
ing, especially  if  a  rubber  buffer  be  also  fixed. 
The  top  and  bottom  of  the  slate  divisions, 
and  also  the  door,  should  have  a  cast  iron 
grooved  capping  to  connect  each  width  together, 
and  the  several  widths  of  slate  should  be 
clowelled  together  with  copper  or  gunmetal 
dowels.  The  room  containing  the  slipper 
bath-rooms  should  be  at  least  12  ft.  high  if 
there  is  a  flat  ceiling,  but  an  open  roof  is  to 
be  preferred,  with  a  closed  lantern  light  over, 
which  will  adequately  light  the  central  corridor. 
There  should  be  an  external  window  to  each 
bath-room  if  possible.  Where  the  exigencies 
of  the  site  do  not  allow  of  all  classes  of 
slipper  baths  being  on  the  ground  floor,  it  is 
usual  to  place  the  first-class  on  the  floor  above. 
The  baths  are  either  porcelain  or  the  newest 
type  of  enamelled  iron,  and  should  be  of 
the  pedestal  pattern.  Porcelain  is  often 


objected  to  on  account  of  its  coldness.  A 
wooden  top  should  be  provided  over  the  bath, 
of  unpainted  yellow  pine,  1^  in.  thick  ;  also 
a  seat,  and  hooks  for  clothes,  and  a  slatted 
footboard.  Within  the  large  room  containing 
the  several  slipper  taths,  there  should  be  w.c. 
and  urinal  accommodation  and,  situated  near 
the  waiting  room,  an  apartment  should  be 
provided  for  the  attendant.  Each  bath-room 
should  be  connected  with  this  room  by  an 
electric  bell.  If  the  relative  position  of  the 
room  will  permit,  there  could  be  provided  with 
advantage,  a  shute  for  soiled  towels  from  the 
bath-room  to  the  establishment  laundry.  The 
room  containing  the  slipper  baths  should  be 
amply  lit  by  artificial  light.  If  by  gas,  one 
bracket  could  be  fixed  so  as  to  serve  two  baths. 
They  will  probably  be  kept  alight  the  whole 
evening,  but  if  electricity  be  available,  a  light 
could  be  provided  in  each  bath,  each  controlled 
by  a  separate  switch.  The  locks  for  the  bath- 
room doors  should  be  of  a  simple  kind,  capable 
of  being  drawn  back  with  a  knob  from  inside, 
and  opened  with  a  key  by  "the  attendant. 
These  slipper  baths  should  be  warmed  with 
pipes  or  hot  air  as  previously  described. 

SUPERINTENDENT'S  APARTMENTS.  -  -  There 
must  be  a  suite  of  apartments  for  the  bath 
superintendent,  generally  consisting  of  six  or 
seven  rooms  and  arranged  in  the  front  of  the 
building  on  the  upper  floor. 

ESTABLISHMENT  LAUNDRY. — There  must  also 
be  an  establishment  laundry  where  the  towels 
and  bathing  costumes  are  washed.  This  room 
is  generally  in  the  basement,  and  contains  a 
mechanical  washer,  a  boiling  and  rinsing  tank, 
a  hydro  extractor  and  mangle,  all  driven  by 
machinery.  Also  a  set  of  drying  horses,  con- 
taining about  twelve  divisions  according  to 
the  size  and  requirements  of  the  premises. 
The  heat  might  very  well  be  circulated  by  a 
small  motor  fan.  In  all  respects  the  horses 
should  be  constructed  in  the  manner  described 
under  that  head  in  the  article  on  Public  Wash- 
houses.  The  motive  power  for  all  the 
machinery  might  with  every  economy  and 
convenience  be  electricity,  if  it  is  available,  as 
it  is  most  important  to  economise  labour  and 


45 


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do  away  with  constant  attendance  of  the  staff. 
The  boiler-house  should  be  so  placed  that 
there  may  be  a  good  height  for  circulation  of 
water  to  the  various  baths.  It  should  also  be 
so  placed  that  a  boiler  can  be  taken  in  and 
out  without  causing  much  damage  to  the 
building.  Convenience  for  taking  in  coal 
should  be  considered. 

STORE  ROOM. — A  store  room  for  towels, 
bathing  costumes,  soap,  &c.,  should  be  pro- 
vided and  fitted  with  clean  wooden  racks. 
The  room  should  be  heated  and  ventilated. 

THE  BOILER-HOUSE. — It  will  probably  be 
found  that  three  boilers  will  be  required,  of 
Cornish  or  Lancashire  type,  with  a  length  of 
say  30  ft.  and  a  diameter  of  6  ft.  to  6  ft.  6  in. 
each.  This  will  be  a  guide  to  the  dimensions 
of  the  room  required.  The  boilers  will  be 
required  to  supply  steam  for  the  swims,  hot 
water  for  the  slipper  baths,  and  hot  water 
and  steam  for  the  wash-houses.  The  water  in 
the  swimming  bath  is  generally  heated  by 
injecting  steam  into  the  bath  full  of  water,  or, 
it  may  be,  by  circulating  the  water  through 
a  calorifier,  which  can  be  done  with  spent 
steam  supplemented  with  a  small  quantity  of 
live  steam,  which  is  certainly  the  cheapest 
and  most  satisfactory  wray  of  keeping  the 
temperature  even  and  properly  distributing 
the  warmed  water.  Ample  storage  for  coal 
must  be  provided.  Each  of  the  boilers  should 
be  capable  of  doing  the  same  work  and  be  of 
similar  construction.  A  large  storage  tank 
for  cold  water  must  be  provided  with  enough 
head  to  quickly  supply  all  water  which  may 
be  required  for  the  slipper  baths,  laundries, 
boilers,  &c.  The  circulating  pipes  are  laid 
to  the  swimming  bath  along  the  subway 
arranged  around  the  tank,  and  all  other  pipes 
and  wastes  are  laid  in  channels  formed  so  as 
to  be  capable  of  easy  inspection  and  covered 
with  chequered  plating.  It  is  a  great  con- 
venience to  place  a  2  in.  pipe  across  the  width 
of  the  swimming  baths  at  the  shallow  end 
with  perforations  for  spraying  cold  water 
along  the  surface  of  the  water  towards  the 
deep  end,  and  so  driving  out  any  scum  which 
may  collect.  The  fittings  for  supplying  hot 


and  cold  water  for  the  slipper  baths  should 
be  of  a  simple  character  and  capable  of  pro- 
perly mixing  the  hot  and  cold  water.  Such 
fittings  are,  of  course,  controlled  from  outside 
the  bath-room  by  the  attendant. 

THE    TEMPORARY   FLOOR.  —  If   the   bathing 
hall  is  to  be  used  as  a  place  for  public  meet- 
ings, the  bath  must  be  covered  over  with  a 
substantial  floor.      It   is  important  that  the 
substructure  should  be  strong  and  the  boarded 
covering   framed   so   as   not   to   creak  when 
persons  wralk  across  it.     The  floor  which  is 
illustrated  was  designed  by  the  author  with 
these  objects  in  view.     The  trusses  arranged 
across  the  bath  were  in  three  sections,   the 
headpiece  9  in.  by  3  in.,  the  sill  6  in.  by  3  in., 
uprights  7  in.  by  2£  in.,  struts  5  in.  by  2^  in. 
The    top   of   the   headpiece   was   notched   to 
receive  joists  which  were  7  in.  by  2^  in.  and 
18  in.  apart.     These  joists  were  also  partly 
notched  to  fit  on  to  the  trusses  and  were  in  as 
long  lengths  as  could  be  obtained,  but  so  that 
their  ends  "  broke  joint."     The  top  surface  of 
the  joists  was  level  with  the  gangways  around 
the  bath,  so  as  to  allow  the  wooden  floor  to 
cover  the  entire  area.     Between  these  cross 
trusses  there  were  placed  two  rows  of  longi- 
tudinal trusses  having  6  in.  by  3  in.  head,  sill 
and  uprights,  and  6  in.  by  1£  in.  cross  bracing 
screwed  on  to  each  side.      Each   truss   was 
secured  to  its  neighbour  by  a  hasp  and  staple — 
the  staple,  however,  being  in  the  form  of  a 
peg  which  secured  itself  when  turned.     It  was 
desirable  for  dancing  that  the  joints  of  the 
boards  should  be  in  the  direction  of  the  length 
of  the  bath.     The  flooring  consisted  of  6  in. 
by  1£  in.  tongued  and  grooved  boards,  screwed 
to  6  in.  by  1^  in.  cross  bearers.     The  floor 
was  formed  into  sections  6  ft.  by  4  ft.     Three 
bearers  were  provided  to  each  section,  and  as 
the  end  of  each  bearer  projected  2  in.  beyond 
the  side  of  the  boarding,  each  section  became 
interlocking  and  self-securing,  and  its  united 
weight   kept   it   rigid.       A   specially   formed 
section,  tapered  down,  was  provided  near  the 
doorway   and   the    joint    between    the   wood 
section  and  the  tiled  floor  covered  with  a  mat. 
A  trap-door  in  one  section  gave  access  to  the 


46 


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MUNICIPAL   AND   SANITAEY   ENGINEERING. 


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bath  where  it  might  have  been  necessary  for 
an  entrance  to  be  obtained  to  wedge  up.  It  is 
important  that  a  floor  of  this  kind  should 
have  a  special  place  in  which  it  can  be  stored 
away,  as  each  section  should  be  laid  flat  and 
kept  from  twisting  by  the  weight  of  the 
members  above.  Each  part  of  the  floor  is 
numbered  and  laid  in  its  place  according  to 
plan. 

CONTINUOUS  FILTRATION  OF  THE  WATER  IN 
THE    SWIMMING    BATH. — It   is    impossible    to 


instance  the  general  run  of  one  filling  of  the 
bath  with  water,  which  will  probably  remain 
fit  for  use  for  three  days.  It  may  be  con- 
sidered quite  pure  for  say  one  or  two  hours ; 
at  the  end  of  a  day  it  will  present  the  appear- 
ance of  being  different  from  drinking  water, 
but  at  the  end  of  three  days  it  becomes 
necessary  to  discontinue  its  use,  and  yet  some 
swimmers  bathe  in  it  up  to  the  last  moment. 
The  plant  in  question  never  allows  the  water 
to  get  beyond  the  impurity  of  an  ordinary 


FIG.  3. — Continuous  Filter. 


work  a  public  bath  so  that  it  will  be  self- 
supporting  in  the  matter  of  current  expenses. 
The  capital  charges  are  heavy  and  the  cost  of 
maintenance  and  repairs  also  very  great, 
consequently  everything  should  be  done  to 
lessen  the  latter  as  much  as  possible.  But  it 
is  not  with  that  object  principally  in  view  that 
a  system  of  systematic  filtration  has  been 
adopted  ;  it  is  for  the  purpose  of  keeping  the 
water  at  one  degree  of  continuous  purity  that 
the  installation  has  been  in  use.  Take  for 


bath  water  two  or  three  hours  old,  and  the 
water  used  with  this  system  remains  in  use  at 
the  Rotherhithe  Baths,  where  the  author  has 
installed  the  scheme,  for  three  or  four  months 
at  a  time,  including  the  summer  season.  The 
results  have  been  tested  both  chemically  and 
bacteriologically  by  eminent  analysts  and 
pronounced  perfectly  satisfactory,  while  the 
minor  question  of  economy  is  equally 
gratifying  to  the  Council. 

The  following  advantages  are  claimed,  for 


47 


BAT 


ENCYCLOPEDIA   OF 


BAT 


continuous  filtration  : — (1)  The  water  is  never 
allowed  to  get  into  an  unclean  state,  such  as 
may  be  the  experience  of  the  last  bather  in 
water  ready  to  be  thrown  away  under  the  old 
system.  (2)  The  water  is  uniformly  heated 
throughout  at  all  times,  and  those  cold  areas 
which  exist  during  the  first  hour  or  two  in 
water  heated  after  filling  are  avoided.  (3)  A 
total  absence,  even  in  a  crowded  bath,  of  that 
close  "  body "  smell  so  well  known  in  the 
atmosphere  of  most  public  swimming  baths 
which  are  much  used.  (4)  A  continuous 
current  of  water  is  maintained  through  the 
bath.  (5)  Economy  of  water.  (6)  Saving  of 
time  of  the  employees  attending  in  the  early 
hours  of  the  morning  to  heat  up  a  fresh  bath. 
In  the  purification  of  the  water  there  are 
three  different  processes  engaged,  viz.  (1) 
mechanical,  (2)  biological,  and  (3)  chemical ; 
and  although  the  result  is  the  same,  viz.,  the 
conversion  of  complex  organic  compounds 
into  simpler  ones,  it  is  difficult  to  apportion 
the  exact  share  which  each  takes  in  producing 
the  final  result.  In  the  first  place,  there  is 
the  mechanical  cleansing  of  the  water  from 
the  coarser  impurities  by  the  filter.  This  is 
self-evident,  and  needs  no  explanation. 
Naturally,  the  finer  the  material  in  the  filter, 
and  the  thicker  the  layer  through  which  the 
water  has  to  pass,  the  more  effectual  this  will 
be.  The  next  process,  the  biological,  also 
takes  place  in  the  filter  and  is  probably  due 
to  the  activity  of  anaerobic  organisms  in  its 
interstices.  These  organisms  assist  in  split- 
ting up  the  complex  organic  matters  mentioned 
through  their  various  stages,  viz.,  ammonia 
and  nitrites,  into  the  end  products  known  as 
nitrates.  The  periodical  cleansing  of  this 
filter  by  "  live  "  steam,  no  doubt,  puts  a  tem- 
porary check  on  this  action,  but  when  the 
water  is  put  through  the  filter  again,  the  epar 
will  soon  regain  a  fresh  supply  of  anaerobes. 
The  third  cleansing  process  (chemical)  is 
that  due  to  the  exposure  of  the  water  to  the 
atmosphere  by  the  aerator  on  the  roof.  This 
is  principally  one  of  oxidation,  in  which  the 
greater  portion  of  the  organic  matter  will  be 
destroyed  by  the  combination  of  the  atmo- 


spheric oxygen  with  it,  the  final  products  being 
water,  carbonic  acid,  and  an  innocuous  resi- 
due. Saline  ammonia  and  any  volatile 
animal  products  in  the  water  will  also  be  got 
rid  of  during  this  process  of  aeration.  This, 
no  one  who  takes  the  trouble  to  visit  the 
aerator  can  doubt,  for  the  sense  of  smell  will 
convince  him  that  a  number  of  such  products 
are  freely  given  off. 

The  following  is  a  description  of  the  work- 
ing of  the  scheme  : — The  water  is  first  put 
into  the  first-  and  second-class  baths  direct 
from  the  main,  and  then  alternately  allowed 
to  gravitate  to  a  strainer,  which  eliminates, 
such  solid  particles  as  portions  of  bathing 
costumes,  grit,  hair-pins,  &c.,  &c.  The  water 
is  afterwards  raised  by  pumps  to  the  aerating 
tower,  which  is  fixed  on  the  roof,  by  which 
means  the  whole  of  the  water  is  broken  up 
and  exposed  to  the  atmosphere,  and  thus  it 
receives  a  fresh  supply  of  oxygen.  The  water 
then  descends  and  passes  through  the  filter, 
which  purifies  it.  Then  it  passes  through  a 
heater,  which  is  worked  by  the  spent  steam 
from  the  pumps  and  from  other  parts  of  the 
building,  producing  a  temperature  of  74°  Fahr., 
and  after  this,  the  water  is  delivered  into  the 
shallow  end  of  the  bath,  again  fit  for  bathing. 
This  process  is  continuous.  The  filter  is 
cleansed  about  every  second  or  third  day,  by 
passing  about  2,000  gallons  of  water  and  live 
steam  the  reverse  way  through  the  filtering 
media,  and  washing  the  accumulation  out  into 
the  sewer.  The  first-  and  second-class  baths 
are  worked  alternately,  and  the  plant  will  deal 
with  20,000  gallons  per  hour  ;  the  water  in  the 
large  swim  being  changed  every  four-and-a 
half  hours  by  this  process  of  circulation.  As 
the  baths  are  situated  near  manufacturing 
works,  there  is  a  tendency  for  dust  to  blow  in 
through  the  louvre  ventilators  during  the 
night,  and  settle  on  the  water ;  therefore  a 
spray  is  used  each  morning  to  clean  off  the 
top  surface,  and  it  also  replenishes  any  water 
lost  by  evaporation  and  that  used  in  the 
emptying  of  the  filtering  chamber  during  the 
periods  of  cleansing. 

The  various  parts  consist  of  (1)  A  strainer 


48 


BAT 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


BOI 


to  intercept  particles  likely  to  obstruct  the 
pumps.  (2)  Two  pumps  to  deliver  the  water 
to  the  aerator.  (3)  An  aerator  to  oxygenate 
the  water,  situated  on  the  roof.  (4)  A  filter 
capable  of  filtering  the  water,  provided  with 
means  of  cleansing  the  filtering  surface  when 
required.  (5)  A  heater-condenser  capable  of 
condensing  the  steam  used  by  the  pump,  and 
of  raising  the  temperature  of  the  water  from 
about  50°  to  74°  F.,  when  supplied  with 
auxiliary  live  steam. 

Aerator. — The  aerator  consists  of  cast-iron 
"  A "  frames  supporting  a  copper  perforated 


FIG.  4. — Aerator. 

pipe.  These  "  A  "  frames  are  connected  to- 
gether by  means  of  light  girders  at  intervals, 
and  fixed  to  these  girders  are  perforated  zinc 
trays,  having  sufficient  number  of  perfora- 
tions to  allow  the  required  amount  of  water  to 
pass  through  in  a  large  number  of  very  fine 
streams.  The  aerator  is  fitted  with  three  of 
these  trays.  The  bottom  of  the  aerator  con- 
sists of  a  galvanized  sheet-iron  tank  to  receive 
the  aerated  water.  The  end  frames  of  the 
aerator  are  boarded  in,  and  the  sides  are 
fitted  with  a  number  of  louvre  boards,  so 
arranged  that  the  air  can  have  free  inlet  and 
outlet  to  the  water,  and  that  any  water 
M.S.E.  49 


splashing  on  to  these  boards  will  run  back 
again  into  the  tank.  Rough  plate  glass  is 
no.v  being  substituted  for  wood  in  the  louvres, 
so  as  to  admit  more  light  to  the  water. 

Filter. — The  filter  measures  14  ft.  by  6  ft. 
6  in.  by  5  ft.  6  in.  deep,  and  is  of  sufficient 
surface  to  deal  with  20,000  gallons  of  water 
per  hour.  The  filter  tank  consists  of  cast-iron 
plates.  The  filter  is  arranged  inside  with  a 
rib  which  supports  a  couple  of  filter  plates 
of  wrought  iron,  these  filter  plates  having  a 
sheet  of  wire  gauze  in  between,  and  so 
arranged  that  the  holes  in  the  plates  are 
opposite  one  another.  In  that  part  of  the 
filter  below  the  filter  plates  a  cast-iron  pipe  is 
connected  to  a  valve  on  the  outside  of  the 
filter.  This  cast-iron  pipe  has  a  large  number 
of  1J  in.  wrought-iron  pipes  branching  out 
under  the  whole  of  the  filter  surface,  these 
pipes  having  a  number  of  very  small  holes 
arranged  in  them,  so  that  the  delivery  of  air 
for  flushing  purposes  may  be  distributed  as 
evenly  as  possible  on  to  the  surface  of  the 
filtering  material.  The  filtering  material 
consists  of  gravel  of  special  quality,  about 
18  in.  or  19  in.  deep,  supported  on  the 
above-mentioned  plates.  The  cost  of  the  plant 
and  builders'  work  was  £965  ;  at  present  the 
scheme  shows  a  saving  of  £188  5s.  4d.  on  the 
year's  working.  R.  J.  A. 

Bell's  Water  Filters. — (See"  MECHANICAL 
FILTRATION.") 

Benching. — A  raised  step  at  the  bottom  of 
a  manhole  so  formed  that  any  liquids  falling 
on  same  may  flow  off  into  the  drain. 

Boilers. — A  satisfactory  steam  power  plant 
must,  in  addition  to  having  an  efficient 
engine,  also  have  an  economical  boiler,  the 
design  and  setting  of  which  should  be  such  as 
to  use  the  heat  generated  to  the  best  possible 
advantage  with  a  minimum  cost  for  fuel- 
Different  types  of  boilers  are  required  for 
different  powers  and  conditions  of  working, 
and  it  is  necessary  to  investigate  boiler 
efficiency  as  distinct  from  that  of  the  engine 

E 


BOI 


ENCYCLOPEDIA   OF 


BOI 


in  order  to  allocate  to  the  proper  quarter  any 
wastes  taking  place.  The  principal  types 
of  boiler  in  use  are  the  Cornish,  the  Lan- 
cashire, the  Galloway,  the  Babcock  and 
Wilcox,  and  other  forms  of  water-tube  boilers. 
In  the  Cornish  boiler  there  is  one  central 
flue  containing  the  furnace,  with  side-flues  and 
bottom-flue.  This  type  works  at  a  pressure  of 
about  80  Ibs.  per  square  inch,  is  only  suited 
for  comparatively  small  powers  ranging  from 
40  to  150  h.p.,  and  is  made  from  4  ft.  to  6  ft. 
6  in.  diameter.  The  Lancashire  boiler  is 
similar  to  the  Cornish  in  general  arrange- 
ment and  setting,  but  has  the  distinguishing 
feature  of  two  central  flues  instead  of  one. 
These  boilers  are  made  in  sizes  varying  from 
about  80  h.p.  (14  ft.  by  5  ft.  6  in.)  to  390  h.p. 
(30  ft.  by  8  ft.  6  in.),  and  for  working  pressures 
up  to  160  Ibs.  to  the  square  inch.  Lan- 
cashire boilers  are  steady  steam  producers, 
have  a  large  water  capacity,  and  are  easily 
accessible.  For  ordinary  waterworks  pumping 
purposes  and  for  other  general  use  it  is  the 
most  serviceable  and  economical  form,  that 
can  be  used.  Galloway  boilers  have  two 
circular  furnaces,  extending  about  one-third 
the  length  of  the  boiler,  and  which  open  into 
a  wide  flue,  in  which  are  inserted  Galloway 
tubes.  Pockets  placed  at  each  side  of  the 
wide  flue  just  beyond  the  furnaces  contract 
the  area  and  divert  the  furnace  flames  towards 
the  centre  tubes.  These  boilers  have  evaporated 
over  12  Ibs.  of  water  per  pound  of  coal. 
Water-tube  boilers  are  usually  classed  in  two 
main  divisions,  viz.,  those  with  large  tubes  and 
those  with  small  tubes.  The  Babcock  and 
Wilcox  boiler,  with  inclined  tubes  connected 
into  headers  at  each  end,  and  these  in  turn 
communicating  with  the  steam  drum,  is  an 
example  of  the  first  division,  whilst  the 
Yarrow  and  the  Thornycroft  boilers,  having 
a  number  of  small  tubes  communicating 
with  upper  and  lower  drums  are  examples 
of  the  second  class.  Water-tube  boilers  have 
a  small  water  capacity,  are  quick  steaming, 
give  systematic  circulation  of  water,  are  light 
and  portable,  and  are  suitable  for  the  quick 
generation  of  high  pressure  steam.  Their 


disadvantages  are  liability  to  smoke  with 
bituminous  coals,  smallness  of  thermal 
capacity  and  unsteadiness  of  steaming, 
increased  complication  and  cost  of  repairs, 
and  the  necessity  of  using  pure  water  to  avoid 
incrustation  of  the  tubes. 

BOILER  EFFICIENCY. — The  weight  of  water 
evaporated  by  a  boiler  from  a  given  tem- 
perature per  pound  of  fuel  used  is  in  practice 
taken  to  represent  the  efficiency  of  the  boiler 
in  the  same  way  that  the  weight  of  steam  used 
by  an  engine  per  i.h.p.  hour  is  regarded  as 
the  measure  of  its  efficiency.  A  more  accurate 
statement  of  the  efficiency  of  the  boiler  is 
made  by  separately  calculating  the  heat  units 
given  to  the  water  and  the  heat  units  obtained 
by  the  combustion  of  1  Ib.  of  coal,  so  that  the 
ratio, 

Heat  units  given  to  the  water       , ,     t    -i       ,*.   • 

—  =  the  boiler  efficiency. 
Heat  units  trom  coal 

A  much  higher  percentage  of  efficiency  may 
be  obtained  from  a  good  boiler  properly  set 
and  fired,  than  from  the  steam  engine.  A 
boiler  when  worked  with  the  best  fuel  under 
the  best  conditions  will  deliver  to  the  engine 
as  much  as  75  %  of  the  theoretical  heat 
of  the  coal.  The  combustion  of  a  pound 
of  pure  carbon  yields  14,500  heat  units,  which, 
if  fully  used,  will  evaporate  into  steam  at 
atmospheric  pressure  15  Ibs.  of  water  from 
212°  F.  In  practice,  the  evaporations  of 
boilers  range  from  about  7  Ibs.  up  to  about 
13  Ibs.  of  water  per  pound  of  combustible 
according  to  the  type,  arrangement,  and 
efficiency  of  the  boiler  and  furnace  and  the 
quality  of  the  coal.  An  average  evaporation 
of  10  Ibs.  of  water  per  pound  of  coal  is  ordin- 
arily considered  a  satisfactory  result.  In 
addition  to  the  ordinary  Lancashire  boilers, 
others  giving  first-class  evaporative  results 
are,  the  Galloway  breeches  boiler,  the 
Babcock  and  Wilcox  water-tube,  and  the 
Climax  water-tube  boiler.  In  seeking  econo- 
mical results  in  a  steam  generating  plant 
it  must  be  remembered  that  such  a  plant 
consists  of  two  parts,  the  furnace  and  the 
boiler,  each  of  which  must  efficiently  perform 
its  share  of  the  work.  The  function  of  the 
50 


BON 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BOR 


furnace  is  to  properly  consume  the  fuel  and  to 
procure  the  greatest  amount  of  heat  from  a 
given  weight  consumed.  The  function  of  the 
boiler  is  to  utilise  the  fullest  possible  quantity 
of  heat  thus  generated  in  the  furnace  and  to 
transfer  the  same  into  useful  effect  by  evap- 
orating the  maximum  possible  of  water  into 
steam.  W.  H.  M. 

Boning  Rods.  —  A  set  of  boning  rods 
consists  of  three  exactly  similar  T-shaped 
wooden  frames.  Boning  rods  are  used  by 
drain  layers,  paviours,  and  other  workmen  in 
performing  simple  levelling  operations,  such 
as  setting  out  a  level  line,  extending  a  gradient, 
or  ascertaining  the  intermediate  levels  between 
two  points.  To  set  out  a  level,  one  boning 
rod  is  erected  at  the  starting  point  and 
another  some  feet  away  from  it  and  a  straight 
edge  laid  across  their  tops ;  the  second  boning 
rod  is  raised  or  lowered  until  a  spirit  level, 
placed  at  the  centre  of  the  straightedge  shows 
it  to  be  exactly  horizontal.  A  third  boning 
rod  is  set  up  at  an  equal  distance  from  the 
second  and  the  process  repeated,  except  that 
the  straightedge  should  be  reversed.  The 
second  boning  rod  (No.  2)  may  now  be 
removed  ;  Nos.  1  and  3  will  be  truly  level  as 
any  error  in  the  straightedge  or  spirit  level 
will  have  been  neutralised.  A  gradient  can 
be  set  out  by  first  obtaining  a  level  line  and 
then  raising  or  lowering  the  third  rod  to  the 
required  distance.  A  line  can  be  extended  by 
sighting  across  the  tops  of  two  boning  rods 
and  raising  or  lowering  a  third  until  the  tops 
of  all  three  are  exactly  in  line.  Similarly, 
intermediate  levels  may  be  determined  by 
placing  boning  rods  on  the  outside  points  and 
sighting  on  to  a  third  one  between  them. 

In  actual  work  pegs  are  driven  into  the 
ground  for  the  rods  to  rest  upon  and  obviously 
the  height  of  these  pegs  will  indicate  the 
variation  of  the  ground  surface.  (See  "LEVEL- 
LING, GENEKAL  PRINCIPLES  OF.")  E.  L.  B. 

Borewells. — Bored  steel-lined  tube  wells 
are  now  very  largely  employed  for  access  to 
underground  water  for  public  supply  and  also 


for  numerous  trade  purposes.  Given  average 
success,  water  obtained  in  this  way  commonly 
costs  from  3d.  to  4d.  per  1,000  gallons  inclusive 
of  interest  on  capital  and  working  expenses. 
Unless  the  water-bearing  capacity  of  a  district 
has  been  well  tested  by  previous  borings,  the 
initial  steps  towards  obtaining  underground 
water  is  necessarily  accompanied  by  consider- 
able risk,  as,  although  the  geological  features 


FIG.  1. — Drilling  Apparatus. 

may  seem  favourable,  nothing  short  of 
the  expenditure  of  the  necessary  money  of 
sinking  a  fair-sized  trial  boring,  followed  by 
continued  pumping  operations,  can  be  relied 
upon.  Great  improvements  have  been  made  of 
recent  years  for  expeditiously  sinking  borings 
of  this  character.  They  are  now  made  almost 
exclusively  by  percussive  mechanism  with  the 
aid  of  a  great  variety  of  ingeniously  contrived 
tools  adapted  for  piercing  the  various  classes 
of  strata  met  with.  A  typical  modern  surface 
plant,  as  used  by  the  well-known  firm  of 
51  E  2 


BOR 


BOR 


C.  Isler  &  Co.,  for  raising  and  lowering  the 
tools  in  the  boring  is  shown  in  Fig.  1.  It 
consists  of  wrought- iron  tubular  sheer  legs 
and  winch,  and. is  well  adapted  for  expeditious 
sinking  and  convenient  of  transport.  Steam- 
winch  may  also  be  fitted. 

A  considerable  variety  of  tools  are  employed 
in  connection  with  such  a  plant  for  the 
purpose  of  meeting  the  various  emergencies 
of  the  work  as  they  arise.  The  principal  of 
these,  as  illustrated  in  Fig.  2,  are : — 

1.  Clams   for    suspending    and    screwing 
tubes. 

2.  Worm  auger  for  loosening  compact  soils. 

3.  Clay  auger. 

4  &  5.    Flat   chisel   for  rocky   and   hard 
strata. 

6.  Auger   nose    shell    for    bringing    soils 
broken  up  by  the  chisel. 

7.  Flat  bottom  shell  for  sandy  soil. 

8.  Shoe-nose  shell. 

9.  Latch  tool  for  picking  up  pipes  from  a 
bore-hole. 

10.  Spring  dart  for  same  purpose. 

11.  Bell  screw  for  cutting  thread  on  rods 
broken  in  bore-hole. 

12.  Bell  box  for  picking  up  rods  in  case  of 
breakage. 

13.  Spiral    worm     for    extracting    broken 
rods,  &c. 

14.  Swivel  rod. 

15.  Crow's  foot  for  extracting  broken  rods. 

16.  Eod  joints. 

17.  Spiral  worm  for  extracting  rods. 

18.  V-chisel  for  rocky  strata,  &c. 

19.  T-chisel  for  ditto. 

20.  Rimer  for  enlarging  bore-hole. 

21.  Lifting-dogs  for  raising  rods. 

22.  A  and  B,  rod  tillers  for  working  rods. 

23.  Hand  dogs  for  screwing  rods. 

24.  Spring  hook. 

25.  Boring  rod  with  screwed  ends. 

A  complete  set  of  tools  for  boring  to  400  ft. 
deep,  with  wrought-iron  sheer  legs,  fitted  with 
the  necessary  gearing  and  fast  and  loose 
pulleys,  costs  about  £150. 

Drilling  through  sand,  gravel,  clay  or  soft 
rocks  is  also  very  expeditiously  done  by  what 


is  known  as  the  hydraulic  washing  system  in 
which  the  boring  rods  and  chisel  are  hollow 
to  enable  water  to  be  pumped  downwards 
through  them,  which  has  the  effect  of  washing 
all  debris  to  the  surface,  thus  obviating  the 
necessity  of  removing  the  tools  from  time  to 
time  to  the  surface,  for  clearing,  &c.  The 
rods  and  chisels  are  lifted  and  dropped  as  in 
the  ordinary  percussion  system,  the  water 
being  forced  down  at  the  same  time.  In 
suitable  soils  this  is  one  of  the  most  efficient 


FIG.  2.— Drilling  Tools. 

and  expeditious  methods  available.  Boring 
through  rocks  or  solid  formations  is  more 
advantageously  done  by  means  of  the  Rotary 
Shot  Boring  gear  shown  in  Fig.  3,  which 
has  been  designed  to  replace  the  more  costly 
method  of  diamond  rock  drills.  The  shot  is 
fed  into  the  hollow  boring  rods  and  carried 
downwards  by  means  of  water,  past  the  core, 
and  eventually  under  the  crown.  The  system 
is  suited  for  the  penetration  of  the  hardest 
rocks.  The  cost  of  boring  depends  largely 
upon  the  depth  and  character  of  the  strata  to 
be  passed  through,  but  in  gravel,  clay,  chalk 
or  other  soft  strata  for  depths  not  exceeding 
500  ft.  the  price  may  lie  between  30s.  and 
60s.  per  foot  according  to  circumstances.  In 
rock  similar  work  may  cost  from  40s.  to  80s. 


52 


BOR 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BOS 


per  foot,  for  borings  not  exceeding  12  in. 
in  diameter,  and  exclusive  of  lining  tubes. 
Where  lining  of  the  bore  is  necessary  wrought- 
iron  lap-welded  steel-socketed  tubes  are  used, 
the  approximate  prices  of  which  are  6  in. 
internal  diameter  10s.  per  foot,  8£  in. 
diameter  17s.  per  foot,  and  11 J  in.  diameter 
25s.  per  foot. 

Other  well-known  methods  of  boring  which 
have    been     successfully    employed    are   the 


STEAM    ROTARY   ROCK   BORING    GEAR. 


FIG.  3. — Drilling  Process  in  operation. 

Kind  -  Chaudron  deep  -  boring  system,  the 
Dru  deep-boring  system,  Mather  &  Platt's 
system,  the  American  rope-boring  system, 
and  deep-boring  by  diamond  drills.  The 
water  from  borewells  is  raised  either  by  means 
of  an  "air-lift"  or  by  the  employment  of 
steam-driven  deep-well  pumps  of  the  ordinary 
type.  For  further  information,  see  also 
articles,  "  WELLS,  ARTESIAN  WELLS,  ABYS- 
SINIAN WELLS,  UNDERGROUND  WATER,  AND 
AIR-LIFT."  W.  H.  M. 


Boston,  U.S.A.,  Sewage  Disposal  at.— 

Boston,  Massachusetts,  U.S.A.,  is  a  city  of 
somewhat  over  half  a  million  inhabitants, 
situated  at  the  upper  end  of  an  elliptical 
harbour,  about  twelve  miles  long  and  six 
miles  wide.  A  considerable  number  of  smaller 
cities  and  towns  are  clustered  thickly  about 
the  larger  municipality,  making  the  popula- 
tion of  Greater  Boston  about  1,250,000. 
The  metropolitan  district  as  a  whole  covers 
an  area  of  nearly  two 
hundred  miles ;  and  it  is 
intersected  by  three  rivers, 
the  Mystic  and  the  Charles, 
which  discharge  at  the  upper 
(N.W.)  extremity  of  the 
harbour,  and  the  Neponset, 
which  enters  on  its  south- 
westerly side.  Originally 
the  sewers  of  the  city  dis- 
charged at  various  points 
(seventy  or  more)  along  the 
water  front.  At  times  of 
heavy  rain  coinciding  with 
high  tides  the  sewage  backed 
up,  and  created  objectionable 
conditions  in  the  lower  part 
of  the  city  ;  and  at  almost 
all  times  there  was  a  serious 
nuisance  in  the  inner  har- 
bour, as  the  sewage  was 
borne  back  and  forth  by 
the  tide.  In  1875  a  joint 
engineering  and  medical 
commission  made  a  study 
of  the  problem  and  recom- 
mended the  construction  of 
two  main  systems  of  intercepting  sewers, 
one  for  the  region  south  of  the  Charles 
river,  including  most  of  Boston  proper,  and 
the  other  for  the  cities  and  towns  north  of 
the  Charles.  The  development  of  the  former 
plan,  the  Boston  Main  Drainage  Works,  was 
begun  almost  at  once,  in  1877,  and  was  com- 
pleted in  its  general  outlines  by  1884.  The 
main  outfall  sewer  for  this  district  discharges 
at  Moon  Island,  near  the  middle  of  the  harbour. 
The  construction  of  the  Main  Drainage  Works 


53 


BOS 


ENCYCLOPEDIA  OF 


BOS 


has  been  carried  out  under  successive  city 
engineers,  J.  P.  Davis,  H.  M.  Wightman  and 
William  Jackson;  Eliot  C.Clarke  was  principal 
assistant  engineer  in  charge  of  construction  up 
to  1884.  Meanwhile  the  State  Legislature  of 
Massachusetts  appointed  various  commissions 
to  consider  the  wider  problems  involved, 
notably  the  Metropolitan  Drainage  Commis- 
sion of  1881  and  the  Massachusetts  Drainage 
Commissions  of  1884  and  1885.  In  1889  the 
State  Board  of  Health  prepared  a  general  plan 
for  a  system  of  intercepting  sewers  to  serve 
the  region  north  of  the  Charles,  and  to  dis- 
charge at  Deer  Island  at  the  mouth  of  the 
harbour.  A  special  board  of  Metropolitan 
Sewerage  Commissioners  (Hosea  Kingman, 
Chairman)  was  created  by  the  State  Legisla- 
ture to  construct  and  operate  the  works, 
outside  of  the  Boston  Drainage  District,  the 
costs  being  apportioned  on  the  several  com- 
munities involved.  Howard  A.  Carson  was 
Chief  Engineer  to  1895  ;  William  M.  Brown 
has  had  entire  charge  of  construction  and 
maintenance  since  that  date.  The  Commis- 
sion constructed  first  an  intercepting  sewer 
along  the  south  bank  of  the  Charles  for  the 
region  to  the  west  of  Boston.  This  entered 
into  the  Boston  Main  Drainage  system  from 
1892  to  1904 ;  and  the  sewage  thence  passed 
to  Moon  Island.  The  North  Metropolitan 
system  for  the  cities  and  towns  north  of  the 
Charles  Eiver  was  essentially  completed  in 
1895 ;  and  has  since  discharged  at  Deer 
Island.  In  1895  a  sewer  was  begun  in  the 
Neponset  Valley;  and  in  1899  construction 
was  begun  on  a  general  high-level  system 
for  the  communities  to  the  south  and  west  of 
Boston.  This  system  was  completed  in  1904. 
It  takes  most  of  the  sewage  which  originally 
passed  from  the  Metropolitan  sewer  on  the 
south  bank  of  the  Charles  into  the  Boston 
Main  Drainage  Works,  and  carries  it  round 
the  south  side  of  the  harbour  to  discharge  at 
Nut  Island  near  the  harbour  mouth.  The 
entire  system  thus  includes  three  main  divi- 
sions— the  North  Metropolitan  sewer,  dis- 
charging at  Deer  Island;  the  Boston  Main 
Drainage  Works,  discharging  at  Moon  Island  ; 


and  the  South  Metropolitan  high-level  sewer, 
discharging  at  Nut  Island. 

The  North  Metropolitan  sewer  serves  certain 
areas  of  Boston,  and  the  cities  and  towns  of 
Winthrop,  Chelsea,  Everett,  Maiden,  Melrose, 
Cambridge,  Somerville,  Medford,  Winchester, 
Woburn,  Stoneham,  Arlington,  Belmont, 
Wakefield,  Lexington  and  Eevere.  The  total 
area  is  90'50  square  miles  and  the  total  popu- 
lation January  1,  1908,  was  estimated  at 
498,640.  Of  this  population  422,065  are 
estimated  as  contributing  sewage.  The  mileage 
of  local  sewers  connected  January  1, 1908,  was 
624'74,  and  the  number  of  connections  65,786. 
The  total  flow  of  sewage  in  1907  averaged 
64,300,000  gallons  per  day.  In  constructing 
the  North  Metropolitan  system,  it  seemed  best, 
in  order  to  avoid  deep  excavation  in  unfavour- 
able ground,  to  provide  for  pumping  several 
times  with  low  lifts  at  each  station.  The 
system  has  three  main  branches  extending  to 
the  northern,  western,  and  southern  portions 
of  the  area.  The  sewage  from  the  western 
portion  (4,000,000  gallons  per  day)  is  lifted 
13J  ft.  at  Alewife  Brook,  and  that  from  the 
southerly  portion  (32,000,000  gallons  per 
day)  is  lifted  about  10  ft.  At  East  Boston, 
and  again  at  Deer  Island,  nearly  the  entire 
volume  of  the  sewage  is  pumped,  the  lift  being 
15  ft.  at  the  first  station  and  6  to  15  ft., 
according  to  tide,  at  the  second.  The  equip- 
ment at  the  last  two  stations  consists  in  each 
case  of  three  submerged  centrifugal  pumps 
with  impellers  8'25  ft.  in  diameter  driven 
by  triple-expansion  Eeynolds-Corliss  engines. 
The  cost  of  pumping  is  $'1079  per  million 
foot-gallons  at  Deer  Island,  and  $'0718  at 
East  Boston.  Between  these  two  pumping 
stations  the  sewage  passes  in  an  8'5-ft. 
inverted  siphon  of  steel,  264  ft.  long,  under 
Shirley  Gut.  After  pumping  at  Deer  Island 
the  sewage  is  disposed  of  by  continuous  under- 
water discharge  through  a  6^-ft.  outfall  sewer 
of  concrete  and  brick.  The  point  of  discharge 
is  1,860  ft.  out  from  the  shore  line  at  high 
water,  and  in  a  powerful  current  setting  in 
and  out  through  the  mouth  of  the  harbour. 
Engineering  problems  of  considerable  interest 


54 


BOS 


MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


BOS 


arose  in  the  construction  and  laying  of  the 
Shirley  Gut  siphon  and  the  outfall  sewer. 
Screening,  carried  out  at  the  various  pumping 
stations  of  the  North  Metropolitan  system, 
intercepted  in  1907  rags,  paper,  &c.,  to  the 
amount  of  2422'2  cu.  yds.  or  2'8  cu.  ft.  per 
million  gallons  of  sewage. 

The  high-level  sewer  of  the  South  Metro- 
politan system  now  serves  about  a  quarter  of 
the  city  of  Boston  and  the  cities  and  towns 
of  Brookline,  Newton,  Watertown,  Waltham, 
Milton,  Hyde  Park,  Dedham,  and  Quincy. 
The  total  area  included  is  102  square  miles, 
and  the  population,  January  1,  1908,  was 
estimated  at  325,090.  Of  this  population 
188,150  are  estimated  as  now  contributing 
sewage.  The  mileage  of  local  sewers  connected 
was  479'51,  and  the  number  of  connections, 
26,019  on  January  1,  1908.  The  total  flow 
of  sewage  for  1907  averaged  40,600,000  gallons 
per  day. 

The  sewage  from  the  northern  part  of  the 
high-level  system,  amounting  to  23,000,000 
gallons  a  day,  is  pumped  at  Ward  Street, 
the  lift  being  about  40  ft.  The  pumps  are 
of  reciprocating  type  with  plungers  48  in. 
in  diameter  and  a  60-in.  stroke,  operated 
by  vertical  triple-expansion  Allis-Chalmers 
engines.  From  Ward  Street  the  sewage  flows 
by  gravity  to  the  outfall  at  Nut  Island.  The 
flow  from  the  southern  and  eastern  part  of 
the  district  enters  for  the  most  part  by  gravity, 
although  about  3,000,000  gallons  a  day  are 
pumped  at  Quincy.  The  main  outfall  sewer 
is  11  ft.  3  in.  by  12  ft.  6  in.,  and  it  discharges 
off  Nut  Island  by  two  60-in.  cast-iron  pipes, 
having  an  aggregate  length  of  10,844  ft.,  and 
laid  under  the  bed  of  the  harbour.  Screens 
are  located  at  the  pumping  stations  and  at 
Nut  Island,  and  the  total  screenings  removed 
in  1907  amounted  to  2735'6  cu.  yds.,  or 
5'0  cu.  ft.  per  million  gallons  of  sewage. 
The  screens  at  Nut  Island  are  four  in  number, 
two  in  each  duplicate  channel  of  the  screen 
room.  They  are  about  12  ft.  square  with  clear 
openings  of  f  in.  between  the  bars,  and  are 
operated  by  small  reversing  engines. 

The  third  and  central  system  of  the  three 


which  discharge  into  Boston  Harbour,  is  the 
Boston  Main  Drainage  Works,  which  serves 
the  central  portion  of  the  city  itself  (E.  S. 
Dorr,  Chief  Engineer).  The  area  is  small, 
only  about  13  square  miles..  The  popula- 
tion in  this  area,  however,  was  estimated 
at  358,372,  January  1,  1908,  and  practically 
all  of  the  houses  are  connected.  There  are 
530'48  miles  of  local  sewers  connected  with 
this  system.  The  number  of  individual  con- 
nections is  not  accurately  known,  but  may  be 
placed  somewhere  between  35,000  and  40,000. 
The  average  daily  flow  of  sewage  in  1907  was 
87,660,000  gallons. 

The  figures  for  the  whole  city  of  Boston, 
including  the  sewers  which  discharge  through 
the  North  and  the  high-level  systems  as  well 
as  the  Boston  Main  Drainage  Works,  are  as 
follows: — Population,  January  1,1908, 614,632; 
total  area,  42'5  square  miles  ;  total  length  of 
sewers,  729'26  miles  ;  average  flow  of  sewage, 
124,200,000  gallons  per  day. 

The  sewage  of  the  Boston  Main  Drainage 
Works  flows  by  gravity  to  the  Calf  Pasture  in 
Dorchester.  At  the  Calf  Pasture  it  is  lifted 
36'5  ft.  and  discharged  through  a  tunnel 
under  Dorchester  Bay  to  the  main  outfall 
sewer  on  Moon  Island.  Here,  as  Moon  Island 
is  situated  near  the  centre  of  the  harbour  and 
not,  like  Deer  Island  and  Nut  Island,  in  strong 
currents  of  deep  water,  the  sewage  is  stored 
in  masonry  tanks  and  discharged  only  on  the 
out-going  tide.  Before  pumping  the  sewage 
is  screened  by  passing  it  through  iron  cages 
working  in  vertical  shafts.  The  screenings 
removed  in  1907  amounted  to  577  tons.  After 
pumping,  and  before  entering  the  tunnel,  the 
sewage  passes  through  two  deposit  sewers, 
8  ft.  wide  and  16  ft.  high,  which  run  side  by 
side  for  a  distance  of  1,260  ft.,  terminating  in 
each  case  with  a  dam  which  keeps  a  level  high 
enough  to  ensure  a  current  velocity  not  ex- 
ceeding 1  ft.  per  second.  The  deposits  are 
moved  by  a  travelling  scraping  and  flushing 
machine,  operated  by  the  current,  and  are 
delivered  to  a  sludge  tank  from  which  the 
liquid  flows  back  into  the  sewer.  The  sludge 
removed  from  the  tank  is  towed  out  to  sea,  by 


55 


BOS 


ENCYCLOPEDIA   OF 


BOS 


scows.  It  ordinarily  amounts  to  10,000  cu.  yds. 
per  year  or  4'5  cu.  yds.  per  million  gallons  of 
sewage. 

The  pumping  station  is  equipped  with  three 
high-duty  engines,  two  of  which  are  compound 
engines,  the  plungers  of  which  are  48  in.  in 
diameter,  with  a  9-ft.  stroke  and  a  nominal 
capacity  of  35,000,000  gallons  a  day.  The 
third  is  a  triple-expansion  engine,  the  plungers 
of  which  are  60  in.  in  diameter,  with  a  10-ft. 
stroke  and  a  capacity  of  72,000  gallons  a  day 
with  seventeen  revolutions  per  minute.  There 
ar<3  also  two  low-duty  engines  with  45-in. 
plungers  and  a  4-ft.  stroke.  The  nominal 
capacity  of  each  engine  is  25,000,000  gallons 
a  day.  The  tunnel  under  Dorchester  Bay, 
between  the  deposit  sewer  and  the  outfall 
sewer,  is  of  brick,  7,160  ft.  long,  and  it  has  an 
inside  diameter  of  7'5  ft.  The  outfall  sewer 
itself  is  5,900  ft.  long,  and  of  horse-shoe 
section,  11  ft.  high  and  12  ft.  wide.  The 
tanks  in  which  the  sewage  is  stored  at  Moon 
Island  are  four  in  number,  and  cover  an  area 
of  about  10  acres.  Their  bottoms  are  of  con- 
crete, and  their  walls  of  granite  blocks,  laid  in 
cement.  The  total  capacity  of  the  four  tanks 
is  about  50,000,000  gallons.  They  can  be 
flushed  out  by  introducing  sewage  under  high 
velocity  at  either  end  of  the  tanks.  Along 
the  nearer  end  of  the  tanks  run  two  sewers, 
one  above  the  other,  the  upper  being  the 
sewer  which  discharges  sewage  into  the  tanks ; 
the  lower,  the  one  which  empties  the  tanks 
into  the  bay.  There  are  two  sets  of  gates  for 
filling  and  emptying  and  flushing  the  tanks  ; 
one  set  is  controlled  by  electro-pneumatic 
switches,  operated  by  compressed  air,  and  the 
other  set  is  controlled  by  a  line  of  shafting. 
The  whole  system  is  driven  by  a  turbine  run 
by  the  sewage  flow.  The  method  of  opera- 
tion is  to  allow  the  reservoirs  to  fill  for  ten 
hours  and  to  discharge  during  the  second  and 
third  hours  of  the  outgoing  tide.  The  total 
amount  of  sewage  discharged  into  Boston 
Harbour  from  the  three  main  outlets  averaged, 
in  1907,  192,500,000  gallons  a  day.  The 
sewage  of  the  Boston  Main  Drainage  Works 
is  studied  daily  at  the  Sewage  Experiment 


Station  of  the  Massachusetts  Institute  of 
Technology:  The  following  table  shows  the 
average  analyses  for  1905 — 1907. 

COMPOSITION  OF  BOSTON  SEWAGE. 
PARTS  PER  MILLION. 


^ 

*s 

4 

•- 

§ 

Suspended 

',    S 

1 

| 

Solids. 

Organic  Xitio^n 

If 

Oxygen  Consumed.  * 

H 

02 

Total. 

Fixed. 

Total   Dissolved. 

< 

Total  Dissolved. 

279 

121 

135 

44 

9-1        5-3 

13-9 

56          43 

*  30  minutes,  100°. 

The  general  results  of  this  method  of 
disposal  have,  on  the  whole,  proved  fairly 
satisfactory.  The  sewage  discharged  at  Moon 
Island  spreads  out  on  the  surface  (the  dis- 
charge is  1  ft.  above  low  water),  and  is  very 
obvious  for  an  hour  or  two  within  an  area 
of  half  a  mile  or  a  mile  in  diameter.  Some 
nuisance  is  undoubtedly  caused  to  passing 
vessels,  and  it  is  said  that  real  estate  in  the 
neighbourhood  has  been  injured  in  value. 
The  Massachusetts  State  Board  of  Health 
made  careful  investigations  of  the  condition 
of  the  harbour  in  1900,  and  again  in  1905, 
and  showed  that  the  chemical  and  bacterio- 
logical evidences  of  pollution  were  manifest 
on  the  out-going  tide  only  in  a  narrow  path 
extending  for  two  miles  and  a  half  from  Moon 
Island,  and  on  the  incoming  tide,  only  in  the 
immediate  vicinity  of  the  outfall  itself.  At 
Deer  Island  and  Nut  Island  where  discharge 
is  continuous,  under  water,  and  in  a  strong 
current,  conditions  are  better.  In  1907  the 
Board  of  Health  pointed  out  that  the  most 
gerious  pollution  of  Boston  Harbour  at  present 
is  not  at  the  main  outlets  at  all,  but  in  the 
upper  portion  of  the  harbour,  where  a  con- 
siderable amount  of  sewage  still  finds  its  way 
in  by  various  unauthorised  channels. 

It  is,  of  course,  probable  that  the  concentra- 
tion of  population  and  the  rising  level  of 
sanitary  standards  will  ultimately  make  some 
other  method  of  disposal  desirable,  at  least 
for  the  Moon  Island  outlet.  In  view  of 
this  contingency  the  Sewage  Experiment 
Station  of  the  Massachusetts  Institute  of 


56 


ERA 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BRA 


Technology  has  for  six  years  been  carrying 
on  experimental  studies  of  the  purification  of 
Boston  sewage  with  the  following  general 
results.  The  most  suitable  method  for  purify- 
ing the  sewage  from  the  city  proper  would  be 
by  filtration  through  trickling  or  perco- 
lating beds.  These  should  be  8  ft.  deep 
and  constructed  of  1|  in.  to  2  in.  stone. 
They  might  conveniently  be  located  on 
Thompson's  Island  near  the  present  Moon 
Island  outfall  and  would  occupy  an  area  of 
50  acres.  It  seems  from  the  experiments 
so  far  conducted  that  it  would  be  more 
economical  to  apply  the  sewage  directly 
to  the  beds  without  septic  treatment,  remov- 
ing only  screenings  and  heavy  detritus. 
After  filtration  the  trickling  effluent  must, 
however,  be  subjected  to  a  sedimentation  of 
two  hours  for  the  removal  of  suspended  solids. 
At  the  same  time  bacterial  purification  may 
be  attained  by  disinfection  with  chloride  of 
lime,  using  about  five  parts  of  available  chlorin 
per  million  gallons  of  sewage.  Preliminary 
estimates  place  the  cost  of  filtration  (including 
capital  charges),  at  about  five  dollars  and 
a  half  per  million  gallons,  and  the  cost  of 
disinfection  at  about  one  dollar  and  a  half  per 
million  gallons.  It  is  quite  possible  that  the 
extension  of  an  outfall  sewer  to  the  outer 
harbour  with  an  under-water  discharge,  pre- 
ceded by  careful  screening,  might  prove  more 
economical  and  equally  satisfactory. 

C.  E.  A.  W 

Bradford  Sewage  Disposal.  —  POPULA- 
TION, AREA,  &c. — The  City  of  Bradford  has  a 
population  of  about  300,000  (1901  census 
279,767),  the  area  being  22,800  acres.  For 
sewage  disposal  purposes,  this  is  divided 
into  ten  districts,  each  having  separate  sewage 
disposal  works,  the  most  important  being  at 
Erizinghall.  At  the  other  works  the  sewage  is 
purified  as  follows  : — 

1.  Eccleshall.  —  Chemical  precipitation  and 
land  filtration,  100  acres  (clay). 

2.  Greengates.  —  Chemical       precipitation, 
straining  filters  (coal),    followed    by  circular 
filter  7  ft.  deep  (coal). 


57 


3.  Idle.  —  Broad  irrigation,    aluminaferric 
being  added  to  the  sewage. 

4.  Heaton. — Septic  tanks  and  contact  beds. 

5.  Thornton. — Chemical  precipitation  (alu- 
minaferric) and  land  filtration. 

6.  Thacldey. — Broad  irrigation. 

7.  Sandy  Lane. — Aluminaferric  circular  pre- 
cipitation tank,  followed    by   shallow  filters 
(engine  ashes). 

8.  North  Bieiiey. — Septic  tanks  and  artificial 
filters,   area  six  acres,    distribution  by  fixed 
jets,   and   also    circular    distributor   236   ft. 
diameter. 

9.  Lower   Wyke. — Sewage   treated    by   the 
Brighouse  Corporation. 

10.  Frizinghall. — In  addition  the  Corpora- 
tion of  Bradford  take  and  treat  the  sewage 
of  the  Yeadon  Urban  District.     This  latter, 
together  with  that  from  Frizinghall  and  the 
first  named  five  districts,  will  be  conveyed  to 
the  Esholt  works,  which  are  being  carried  out 
by  the  Corporation  of  Bradford  at  an  estimated 
cost  of  £1,250,000,   including  cost  of  1,800 
acres  of  land  recently  purchased. 

VOLUME  OF  SEWAGE. — The  volumes  treated 
at  the  different  works  vary,  and  the  trade 
refuse  contained  determines  the  preliminary 
method  of  treatment  in  use. 

The  largest  volume,  13,000,000  gallons  a 
day  (dry  weather  flow)  is  dealt  with  at  Friz- 
inghall. This  sewage  comes  from  the  centre 
of  the  city,  and  is  more  affected  by  liquid  trade 
refuse  than  any  other.  It  contains  some 
6,500,000  gallons  of  liquids  from  the  pro- 
cesses of  wool  scouring,  dyeing,  &c.,  and  in 
consequence  is  highly  charged  with  fatty 
matters  and  organic  matter  in  solution.  The 
fatty  matters  brought  down  in  the  sewage 
amount  to  as  much  as  25  tons  a  day. 
The  oxygen  absorbed  from  permanganate  in 
four  hours  at  80°  F.  is  about  20,  and  the 
albuminoid  nitrogen  3  parts  per  100,000. 

TREATMENT. — The  sewage  is  passed  through 
detritus  tanks  which  remove  10  tons  per  day 
of  heavy  matter,  and  through  screens,  each 
consisting  of  six  sets  of  tynes  set  in  a  com- 
mon shaft,  and  caused  to  revolve  in  the 
sewage,  and  provided  with  an  automatic 


BRA 


ENCYCLOPAEDIA   OF 


BRA 


cleaning  device.  Sulphuric  acid  is  then 
added  to  the  sewage  in  such  quantities  as  to 
give  an  excess  of  about  5  parts  per  100,000 
of  free  sulphuric  acid.  In  this  way  the  sludge 
is  precipitated,  being  deposited  in  settling 
tanks  worked  in  series  on  the  continuous  flow 
system.  The  sludge  produced  contains  an 
average  of  78  %  of  moisture,  and  7  %  of  fatty 
matter. 

SLUDGE. — The  sludge  is  raised  by  compressed 
air  into  the  sludge  pressing  houses,  where  it  is 
screened,  acidified  with  sulphuric  acid,  heated 
to  100°  C  by  exhaust  steam  in  open  vats,  and 
then  passed  through  sludge  "  rams  "  into  64 
filter  presses.  The  presses  are  heated  by 
steam,  and  the  whole  kept  hot  during  the 
process  of  filter  pressing.  In  this  way  the 
fatty  matters  are  kept  fluid,  and  pass  away 
from  the  presses  with  the  press  liquor.  The 
resulting  cake  contains  27  %  of  moisture,  and 
is  sold  for  manure  at  3s.  Qd.  per  ton  f.o.r., 
or  used  for  fuel  on  the  works.  The  fatty 
matter  is  separated  from  the  water,  purified, 
and  sold. 

TANK  EFFLUENT. — The  effluent  water  from 
the  precipitation  tanks,  which  is  acid  in 
reaction,  is  at  present  run  off  into  the  river. 
The  high  content  of  soluble  organic  matter  in 
this  effluent  is  now  the  difficulty  to  contend 
with. 

FILTRATION. — With  regard  to  filtration,  the 
methods  at  present  in  use  at  the  Frizinghall 
works,  and  which  are  necessarily  only  of  an 
experimental  character,  are  the  result  of  the 
work  of  several  years.  A  large  amount  of 
experimental  work  has  been  done,  the  work 
including  researches  on  the  effect  of  filtration 
of  (a)  acid  tank  effluent  (as  discharged  from 
the  tanks) ;  (b)  tank  effluent  neutralised  with 
lime,  magnesium,  barium  salts,  &c. ;  (c)  tank 
effluent  made  slightly  alkaline ;  (d)  tank 
effluent  after  a  secondary  precipitation ;  (e) 
septic  tank  effluents ;  (/)  tank  effluent  con- 
taining a  large  quantity  of  added  sulphuric 
acid. 

The  different  kinds  of  material  tried  have 
been  very  numerous,  amongst  others  tried 
being  coal,  coke,  cinders,  shingle,  and  soil. 


The  depths  of  the  beds  varied  from  12  in.  to 
7  ft.  6  in. 

Any  work  on  the  purification  of  the  Bradford 
effluent  must  be  judged  from  the  standpoint 
of  the  high  content  of  soluble  organic  matter 
in  the  tank  effluent.  The  results  obtained 
prove  that  the  Bradford  effluent  can  be 
efficiently  purified  notwithstanding  the  acidity, 
and  they  further  prove  that  the  acidity  of  a 
tank  effluent  has  no  very  marked  detrimental 
effect  on  the  purification  effected  in  a  filter 
bed.  In  confirmation  of  this  fact,  which  is 
quite  contrary  to  the  view  of  most  authorities 
to-day,  two  series  of  experiments  were  carried 
out.  In  the  first,  two  filters  of  similar 
material  were  worked  side  by  side  under  the 
same  conditions,  one  filter  treating  acid  tank 
effluent,  and  the  other  treating  similar 
effluent,  which  had  been  neutralised  with  lime. 
An  average  of  111  analyses  made  of  each 
effluent  showed  a  difference  of  only  O'll  parts 
per  100,000  of  oxygen  absorbed  in  favour  of 
the  filter  treating  neutral  effluent.  In  the 
second  series,  a  filter  of  cinders  was  supplied 
with  tank  effluent  containing  added  sulphuric 
acid  varying  in  amount  from  25  to  60  parts 
per  100,000.  The  filter  was  worked  for  several 
months,  and  notwithstanding  the  very  large 
amount  of  acid,  satisfactory  results  were 
obtained.  A  large  portion  of  the  acid  was 
neutralised  in  the  bed,  the  acidity  of  the  filter 
effluent  varying  between  7  and  29  parts  per 
100,000.  The  oxygen  absorbed  figure  was  rather 
higher  and  the  albuminoid  ammonia  figure 
always  lower  than  in  ordinar}r  filter  effluents. 
As  regards  the  question  of  nitrification,  the 
Frizinghall  analyses  show  that  with  the  ex- 
ception of  one  set  of  experiments  in  1906-7, 
nitrification  does  not  take  place  unless  the 
acidity  of  the  tank  effluent  is  neutralised  in 
the  bed.  In  the  experiments  referred  to,  the 
effluent  was  one  from  a  coal  bed,  and  in  the 
average  of  over  180  analyses,  although  the 
effluent  showed  a  slight  acid  reaction,  the 
nitrates  averaged  between  '1  and  1*5  parts  per 
100,000. 

BACTERIOLOGICAL  WORK.  —  During  the  last 
18  months  bacteriological  investigations  have 


58 


BRA 


MUNICIPAL   AND   SANITAKY  ENGINEERING. 


BRI 


been  made  at  Frizinghall  on  the  crude  sewage 
and  effluents.  The  chief  result  of  the  work  so 
far  has  been  to  show  that  the  effluents  from 
the  filtration  of  Bradford  sewage  can  be 
brought  to  the  provisional  standards  suggested 
by  Dr.  Houston  in  the  Second  Report  of  the 
Royal  Commission  on  Sewage  Disposal. 

SUMMARY. — On  the  basis  of  the  experimental 
work  done  at  Frizinghall,  therefore,  it  is  held 
that  the  acidity  of  a  tank  effluent  does  not 
exert  any  marked  detrimental  action  on  its 
subsequent  filtration,  either  chemically  or 
biologically  ;  nitrates,  however,  are  not  formed, 
and  their  absence  points  to  the  fact  that  nitri- 
fication is  not  essential  to  the  efficient  purifi- 
cation of  this  sewage.  The  researches  are 
being  continued,  and  the  bacteriological  aspect 
of  the  question  more  thoroughly  investigated. 
The  new  sewage  works  at  Esholt  necessitate  the 
construction  of  an  outfall  sewer  nearly  3£ 
miles  long  and  10  ft.  diameter,  constructed  in 
tunnel  for  a  continuous  length  of  2f  miles. 
Also  an  intercepting  sewer  If  miles  long, 
chiefly  egg-shaped  in  cross  section  3  ft.  6  in. 
by  2  ft.  6  in.,  constructed  in  tunnel  for  one- 
third  of  a  mile,  and  a  pumping  plant  capable 
of  raising  2,000,000  gallons  per  day  to  a 
height  of  120  ft.  At  the  Esholt  end  of  the 
tunnel  the  sewage  will  be  delivered  into 
detritus  tanks  of  1,000,000  gallons  capacity, 
screened,  mixed  with  acid,  and  passed  into 
precipitation  tanks  of  19,500,000  gallons 
capacity,  arranged  with  two  divisions  so  that 
a  second  dose  of  chemicals  can  be  added  if 
necessary.  The  tank  effluent  water  will  then 
be  passed  on  to  60  acres  of  filters  6  ft.  deep, 
rectangular  in  plan  and  arranged  in  half-acre 
beds,  and  on  to  411  acres  of  land  laid  out  for 
filtration  purposes.  The  storm  water  will  be 
passed  through  tanks  of  11,500,000  gallons 
capacity,  and  on  to  50  acres  of  land.  The 
buildings  and  works  necessary  for  the  treat- 
ment of  sludge  will  cover  an  area  of  about  3J 
acres.  The  minimum  volume  of  sewage  to  be 
dealt  with  is  15,000,000  gallons  per  day. 

J.  G. 

Brazing.— (See  "  PLUMBING.") 


Bricks  and  Brickwork  for  Sewers.— 

The  best  materials  procurable  at  a  reasonable 
cost  should  be  used  in  the  construction  of 
sewers,  as  it  is  most  necessary  that  they  should 
be  constructed  and  remain  watertight,  be 
capable  of  resisting  the  crushing  pressure 
exerted  by  the  superincumbent  earth,  and 
withstand  the  erosion  caused  by  the  sand 
and  pebbles  being  carried  along  the  invert,  in 
addition  to  being  unaffected  either  by  the  sewer- 
gas  or  the  chemicals  present  in  the  sewage  of 
manufacturing  towns.  Bricks  for  sewers  may 
be  either  wire-cut  or  pressed,  the  former  being 
commonly  used  for  the 'crown  and  the  latter 
for  the  invert,  they  should  be  well  burnt  in  a 
kiln,  uniform  in  size  and  shape,  with  sharp 
arrises,  free  from  lumps  of  lime  and  pebbles 
and  as  non-absorbent  as  possible.  They 
should  be  comparatively  tough  and  have 
considerable  hardness,  while  the  faces  should 
be  true  to  permit  of  joints  not  exceeding 
T5e  in.  as  a  maximum.  The  colour  of  the 
bricks  is  immaterial,  and  smoothness  of  sur- 
face is  not  an  essential  characteristic  except  in 
the  invert,  provided  the  excrescences  on  the 
exposed  face  are  not  sufficiently  large  to  inter- 
fere with  the  flow,  as  a  thin  layer  of  sewage 
quickly  forms  a  smooth  face  on  the  interior  of 
the  sewer.  The  best  bricks  to  use  are  Blue 
Staffordshire,  Ruabon,  or  Buckley,  which 
will  generally  absorb  less  than  4  %  of 
their  weight  when  soaked  in  water.  Gault 
bricks,  although  absorbing  nearly  20%  of 
water,  may  be  used  on  account  of  their 
hardness  and  durability  provided  they  are  not 
perforated,  or  have  frogs  formed  in  them,  as 
is  frequently  done  to  reduce  their  weight. 
Staffordshire  brindles,  which  are  an  off-pro- 
duct of  blue  burnings,  and  are  variegated  in 
colour  according  to  their  more  or  less  exposed 
position  in  the  kiln,  are  also  suitable.  Broken 
bricks,  burrs,  place  bricks,  grizzles,  or  chuffs 
should  never  be  used ;  soft  bricks  would 
quickly  wear  away.  Any  individual  bricks 
which  do  not  come  up  to  the  standard,  if  not 
too  numerous,  may  be  used  for  backing. 
Bricks  for  sewer  work  should  be  tested  for 
absorption,  hardness,  crushing,  and  freedom 


59 


BRO 


ENCYCLOPEDIA  OF 


BUI 


from  lime.  The  absorption  test  which  to  a 
certain  extent  is  a  general  guide  to  the  quality 
of  the  brick,  can  be  quickly  made  as  follows  :— 
Thoroughly  dry  the  sample  brick,  weigh  it, 
place  in  boiling  water  and  boil  for  20  minutes, 
then  allow  the  brick  to  cool  in  the  water,  and 
after  being  carefully  wiped  dry,  weigh  it  again. 
Generally  speaking,  no  brick  should  be  used 
in  sewer  work  which  absorbs  more  than 
10  %  of  its  weight  in  water.  Another  method 
of  testing  is  to  soak  the  sample  brick 
in  a  strong  solution  of  sulphuric  acid  for  a 
few  days,  when,  if  no  loss  of  weight  occurs  and 
the  brick  otherwise  stands  the  test,  the  con- 
signment may  safely  be  used  in  the  construc- 
tion of  the  sewers.  Brick  sewers  are  usually 
built  either  oval  or  circular,  the  former  section 
giving  a  quicker  velocity  with  a  small  flow 
than  the  latter,  and  usually  a  better  class 
brick,  such  as  a  best  pressed  blue  Stafford- 
shire, is  used  in  the  invert.  Where  bricks  of 
different  kinds  are  used  they  should  all  be 
of  the  same  size  to  properly  bond  together. 
The  bricks  are  laid  in  4£  in.  rings,  of  which 
there  should  never  be  less  than  two,  unless  the 
outer  part  of  the  sewer  is  formed  of  concrete. 
Cement  mortar  (1  part  cement,  2  sand)  should 
be  used  for  jointing,  and  the  joints  should  be 
struck  as  the  work  proceeds.  Bricks  for  cir- 
cular works  of  less  radius  than  8  ft.  should 
be  specially  moulded  to  the  required  taper  to 
prevent  wide  joints  on  the  extrados,  and  the 
various  sizes  should  be  stamped  with  a  dis- 
tinguishing mark.  H.  A. 


Broad   Irrigation.— (See 

POSAL.") 


SEWAGE    Dis- 


Bryan's  Jets.— (See  "  JETS.") 

Building  Construction  in  its  Sanitary 
Aspect. — Walls — Papering — Floors — Windows 
—  Ventilators  —  Chimney  Flues  —  Cupboards  — 
Partitions — Position  of  W.C. — Water  Supply — 
Dustbins  —  Insanitary  Conditions.  —  The  site 
and  aspect  of  the  house  demand  the  first 
consideration,  but  these  will  be  dealt  with 
under  a  separate  heading  later  on.  The  pre- 


vention of  damp  rising  in  or  penetrating 
through  the  walls,  or  downwards  through  the 
roof,  will  also  be  dealt  with  in  a  special  sec- 
tion. Many  important  details  of  construction 
remain  which  will  now  be  reviewed. 

WALLS. — Concrete  under  the  footings  of  the 
walls  is  only  necessary  when  the  soil  is  of 
irregular  density  or  has  insufficient  supporting 
pow?er  without  it,  and  the  foundation  is  then 
widened  so  as  to  reduce  the  intensity  of  the 
pressure  to  half  a  ton  or  one  ton  per  square  foot. 
Modern  bye-laws,  however,  usually  require 
that  not  less  than  9  in.  of  concrete  shall  be 
placed  below  the  brick  footings,  extending 
6  in.  beyond  them  on  each  side,  irrespective 
of  the  soil  below,  as  in  Fig.  1.  The  num- 
ber of  courses  in  the  footings  is  equal  to  the 
number  of  half  bricks,  or  4^  in.,  in  the  thick- 
ness of  the  wall,  each  projecting  2Jin.  beyond 
the  course  above,  so  that  the  bottom  course  is 
twice  the  width  of  the  base  of  the  wall.  Brick 
walls  and  porous  plastering  are  very  beneficial 
to  the  health  of  the  inmates  of  the  dwelling; 
they  allow  of  the  passage  of  a  considerable 
quantity  of  air  without  any  feeling  of  draught; 
they  absorb  the  surplus  moisture  in  the 
atmosphere  of  the  rooms,  and  do  not  allow 
of  condensation  on  the  surface  when  a  rapid 
rise  of  temperature  takes  place,  as  happens 
with  stone  walls,  cement  plastering,  or  var- 
nished papers.  Stone  walls  have  sometimes 
a  half-brick  lining,  or  a  thick  coat  of  plaster- 
ing, which  promotes  the  dryness  of  the  rooms. 
Bricks  should  be  hard  burnt  but  not  too 
dense,  and  should  not  be  glazed  except  where 
they  require  occasional  cleansing,  or  are  used 
to  reflect  light.  In  poor  neighbourhoods  the 
external  walls  at  the  back  of  the  premises 
should  be  lime-washed  every  twelve  months, 
and  all  sculleries  should  be  washed  and  dis- 
tempered at  the  same  time.  Limewash  is 
composed  of  fresh  burnt  chalk  lime,  with  a 
little  aluminit  to  prevent  it  from  rubbingoff  too 
readily.  Internal  plastering  should  be  put  on 
in  three  coats,  the  first  consisting  of  slaked 
chalk  lime  with  1  to  1^  times  its  bulk  of  clean 
sharp  sand,  and  1  Ib.  of  ox  hair  to  every 
2  cu.  ft.  of  "stuff;"  this  is  called  the 


60 


BUI 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


BUI 


"  pricking  up  "  coat.  The  second,  or  "  floating  " 
coat,  consists  of  slaked  lime  with  a  little  white 
hair  added.  The  third,  or  "setting"  coat, 
consists  of  pure  slaked  lime  without  hair, 
and  with  about  25%  of  plaster  of  Paris  to 
expedite  the  setting  and  give  a  slightly  harder 
face.  Stone  lime,  or  hydraulic  lime,  must  not 
be  used  for  plastering  as  it  is  apt  to  contain 
hard  particles,  which  slake  slowly  and  cause 
"  blowing  "  or  blistering. 

PAPERING. — The  most  hygienic  papers  are 
those  known  in  the  trade  as  "  sanitary " 
papers.  They  have  a  smooth  surface  that 
does  not  collect  the  dust  and  they  may 
be  cleaned  with  dough  or  wiped  lightly 
with  a  damp  cloth  without  injuring 
the  paper.  Highly-coloured  papers 
should  be  avoided,  as  they  may  con- 
tain arsenic,  especially  those  having 
bright  green  in  them.  Before  re- 
papering  a  room  the  old  paper  should 
be  stripped  off  and  the  wall  scrubbed 
down  and  any  damage  to  the  plaster- 
ing made  good.  Old  houses,  especially 
in  poor  neighbourhoods,  have  frequently 
seven  or  eight  thicknesses  of  paper  on 
the  walls,  with  the  paste  in  a  more 
or  less  decomposed  state,  and  the  junc- 
tions with  the  mouldings  round  the 
doors  and  windows  gaping  open  and 
forming  a  breeding  and  harbouring 
place  for  fleas  and  bugs. 

FLOORS. — The  basement  floors  of  dwelling- 
houses,  and  ground  floors  where  there  are  no 
basements,  are  usually  of  deal  battens  on  fir 
joists  for  the  living  rooms  and  kitchens,  and 
of  concrete  and  tiles  for  sculleries,  or  concrete 
alone  for  cellars.  .  The  concrete  should  be 
composed  of  1  part  of  Portland  cement,  2  parts 
of  sand,  and  5  or  6  parts  of  broken  stone, 
hard  brick,  clinker  or  flint  gravel.  Coke 
breeze  is  too  porus  to  use  for  the  aggregate 
in  concrete  next  to  the  soil.  The  fir  joists 
are  supported  on  sleeper  walls  at  intervals  of 
4  to  6  ft.  The  external  walls  should  have 
air  bricks  inserted  about  every  6  ft.  to  ventilate 
the  underside  of  the  wooden  floor;  without 
this  precaution  dry  rot  is  very  liable  to  occur. 


A  continuous  course  of  perforated  glazed  tiles 
is  sometimes  adopted  for  this  purpose,  but 
they  let  in  too  much  air  and  cause  a  draught 
through  the  joints  of  the  flooring.  All  floor 
boards  should  be  well  seasoned  to  prevent 
shrinkage  and  a  consequent  opening  of  the 
joints  which  would  let  dust  through  to  collect 
in  the  space  below.  Double  floors  for  upper 
stories,  consisting  of  common  bridging  joists 
in  one  direction  upon  which  the  boards  are 
nailed,  and  ceiling  joists  in  the  opposite  direc- 
tion upon  which  the  ceiling  laths  are  nailed, 
not  only  make  a  stiffer  floor,  but  allow  the 


FIG.  1 . — Ordinary  Foundation  to  Brick  Wall. 
,,     2. — Section  through  Window  Sill. 
,,     3. — Elevation  of  Chimney  Breast. 

air  to  circulate  from  air  bricks  which  should  be 
placed  in  the  outer  walls.  Skirtings  should  be 
plastered  at  the  back  to  obstruct  the  passage  of 
vermin ;  this  also  reduces  the  risk  of  fire  travel- 
ling quickly  up  a  lath  and  plaster  partition. 
Floors  should  not  be  covered  with  an  imper- 
vious material,  such  as  oil-cloth  or  linoleum, 
unless  well  ventilated  below.  Carpets  should 
not  extend  to  the  walls,  it  is  much  more  sani- 
tary if  a  space  of  18  in.  all  round  is  left  un- 
covered and  stained.  The  floors  of  school 
rooms,  hospitals,  and  public  buildings 
generally,  should  be  formed  of  hard  wood 
blocks  laid  on  mastic  with  close  joints,  so  as 
to  leave  no  crevices  for  the  collection  of 
germs.  If  these  floors  are  properly  prepared 


61 


BUI 


BUI 


and  beeswaxed  they  will  be  non-absorbent 
and  readily  cleaned.  Any  floors  that  are 
washed  should  be  dried  as  quickly  as  possible 
by  free  ventilation  from  open  windows. 

WINDOWS  should  bear  some  proportion  to 
the  floor  area,  height  and  shape  of  the  room, 
and  various  rules  are  given  by  different 
authorities ;  for  example,  Sir  W.  Chambers — 
breadth  of  window  should  be  one-eighth  of 
the  sum  of  the  breadth  and  height  of  room, 
and  height  of  window  2  to  2|  times  its  breadth. 
Joseph  Gwilt — 1  ft.  super  of  light  to  every 
100  cu.  ft.  contents  of  room.  Sir  Douglas 
Galton — 1  ft.  super  to  every  50  or  55  cu.  ft. 
in  hospitals.  Eobert  Morris — area  of  window 
surface  should  equal  the  square  root  of  the 
cubic  contents  of  the  room.  J.  S.  Adams — 
width  of  window  should  equal  the  side  of  a 
square  whose  diagonal  is  the  height.  A  com- 
mon rule  is  to  make  the  window  area  one- 
eighth  to  one-tenth  of  the  floor  area.  The 
window-sill  should  be  18  in.  to  36  in.  above 
the  floor,  average  30  in.  The  head  of  the 
window  should  be  carried  up  as  near  the 
ceiling  as  possible,  say  within  12  in.  of  it,  and 
should  be  made  to  open.  Above  the  ordinary 
inside  bead  along  the  bottom  rail  of  the  lower 
sash,  there  should  be  a  piece  of  wood  3  in. 
deep,  to  permit  of  the  bottom  sash  being  raised 
to  that  extent  without  exposing  the  opening, 
as  in  Fig.  2.  This  permits  of  free  ventila- 
tion at  the  meeting  bars  without  objectionable 
draught,  and  is  known  as  the  Hinckes-Bird 
system  of  ventilation. 

VENTILATOKS. — Open  fire-places  are  the  best 
ventilators  in  a  dwelling-house,  but  these 
generally  require  to  be  supplemented  by 
Arnot  valves  in  the  chimney  flue  or  into  a 
separate  ventilating  flue  carried  up  alongside. 
Objection  is  sometimes  made  to  these  valves 
from  the  dirty  stain  surrounding  them,  which 
is  generally  alleged  to  be  due  to  smoke 
escaping  from  the  chimney,  but  is  really  due 
to  the  dust  in  the  air  impinging  upon  the  wall 
owing  to  the  momentum  of  the  particles 
carrying  them  in  straight  lines  instead  of 
allowing  them  to  deflect  with  the  air  current. 
Rooms  without  fire-places  should  have  a 


Sherringham  inlet  ventilator,  Tobin  tube, 
pipe  flue,  or  perforated  zinc  square  from 
ceiling  to  roof  space.  Fire-places  should 
never  be  closed  by  a  board  and  the  register 
door  of  stoves  should  always  be  left  open. 

CHIMNEY  FLUES  should  not  go  straight  up 
but  be  gathered  over  the  wing  in  the  chimney 
breast  and  carried  up  the  side  as  in  Fig.  3. 
The  usual  size  is  14  in.  by  9  in.,  this  being 
the  smallest  size  the  "chimney  boys"  of  the 
eighteenth  century  could  climb,  but  9  in.  by 
9  in.  is  sufficient  in  the  majority  of  cases.  A 
chimney  pot  on  top,  of  a  smaller  sectional 
area  than  the  flue,  causes  the  escaping  hot 
air  and  gases  to  leave  with  a  much  higher 
velocity  and  with  little  increase  of  friction, 
so  that  there  is  less  tendency  to  a  down 
draught.  Chimney  tops  should  be  carried 
higher  than  surrounding  buildings,  or  there 
will  always  be  a  tendency  to  smoke,  but  a 
smoky  chimney  is  sometimes  due  to  the  want 
of  an  inlet  for  fresh  air  to  the  room. 

CUPBOARDS  should  be  of  dwarf  construction, 
say  3  ft.  high,  or  should  be  carried  up  to 
the  ceiling,  or  a  second  cupboard  fitted  above  ; 
a  cupboard  6  or  8  ft.  high  leaves  a  space  on 
top  for  dust  and  rubbish  to  collect. 

PARTITIONS. — Lath  and  plaster  partitions  are 
commonly  used  because  they  are  cheap  and 
can  be  utilised  to  support  the  upper  floors, 
but  they  are  readily  attacked  and  destroyed 
by  fire.  A  brick-nogged  partition,  where  the 
spaces  between  the  uprights  are  filled  in  with 
common  bricks,  is  more  sound-proof  and 
fire-resisting,  and  where  no  superincumbent 
weight  has  to  be  carried  the  "  Mack " 
partition,  of  solid  porous  slabs,  is  to  be 
recommended. 

POSITION  OF  W.C. — The  inside  w.c.  should 
always  be  against  an  external  wall  with  the 
soil  pipe  outside.  There  should  be  a  window 
to  open,  not  less  than  2  sq.  ft.  in  area, 
and  also  an  air-brick  high  up  with  an  orna- 
mental grating  inside,  which  is  always  open. 
It  is  an  advantage  if  the  door  is  at  least 
1  in.  off  the  floor.  If  the  apartment  can  be 
shut  off  from  the  house  by  a  lobby  with  a 
cross  current  of  air  it  will  keep  all  smell  away 


62 


BUI 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


BUR 


from  the  house.  A  w.c.  must  not  be  entered 
direct  from  any  living  room  or  place  where 
food  is  prepared. 

WATER  SUPPLY. — The  service  pipes  should 
be  laid  2  ft.  below  the  ground  to  avoid  the 
effects  of  frost,  and  in  addition  to  the  stop- 
cock in  the  foot-path  required  by  the  water 
company,  another  should  be  placed  imme- 
diately inside  the  house.  The  supply  to  the 
cistern  should  preferably  be  carried  up  an 
internal  wall,  but  if  it  must  go  up  on  the 
inside  face  of  an  outer  wall  it  should  be  boxed 
in,  the  space  being  filled  up  with  cocoa-nut 
fibre.  All  exposed  pipes  in  the  roof  should 
be  lapped  with  gaskin  and  covered  with 
canvas.  Haybands  form  a  cheap  substitute. 
Old  carpet  used  for  this  purpose  simply 
harbours  moth. 

CISTERNS  should  not  be  placed  under  floors, 
but  in  a  cistern  room  in  the  roof  or  attics. 
For  moderately  hard  water,  say,  over  10 
degrees  of  hardness  or  grains  of  lime  salts 
per  gallon,  they  may  be  of  galvanized  iron,  or 
of  wood  lined  with  lead  or  zinc,  but  for  soft 
water  they  should  be  of  slate  with  cement 
joints,  not  red  lead,  which  is  poisonous.  A 
cover  should  be  provided  to  keep  out  dust, 
leaves,  birds,  beetles,  and  mice.  Some  glass 
slates  or  a  skylight  should  be  provided  in  the 
roof  and  the  cistern  should  be  cleaned  out  at 
least  once  a  year.  Many  writers  on  hygiene 
say  that  drinking-water  cisterns  should  be 
cleaned  out  every  month,  but  it  is  really  safer 
to  have  it  done  properly  once  or  twice  a  year, 
than  to  have  the  duty  performed  oftener  in 
a  perfunctory  manner.  The  overflow  pipe 
should  be  3  in.  from  the  top  and  should 
discharge  in  the  open  air,  where  any  leakage 
would  be  seen,  and  not  on  to  a  roof  to  be 
carried  away  by  the  rain  water  guttering. 
The  w.c.'s  must  not  be  flushed  direct  from  the 
drinking-water  cistern,  but  should  have  three- 
gallon  waste  preventer  cisterns  fed  by  a  ball 
cock  in  each. 

DUST  BINS. — Fixed  dust  bins  should  in  no 
case  be  allowed,  portable  covered  galvanized 
iron  sanitary  bins,  holding  2  or  3  cub.  ft., 
should  be  provided  in  towns,  where  they 


63 


can  be  emptied  weekly  by  the  authorities. 
In  the  country  the  animal  and  vegetable 
refuse  may  be  burnt  or  dug  into  the  garden, 
and  the  ashes  used  for  making  up  paths. 

INSANITARY  CONDITIONS.  —  The  principal 
sources  of  unhealthiness  in  dwellings  are : 
building  on  made  ground,  a  wet  sub-soil, 
damp  walls,  rotten  floors,  insufficient  depth 
below  floors,  dead  vermin,  drains  untrapped 
or  leaking,  want  of  ventilation,  ventilating 
shafts  improperly  placed,  poisonous  wall 
papers,  non-removal  of  old  papers,  leakage  of 
gas,  broken  slates  and  defective  gutters,  low 
ceilings  and  small  windows,  fire-place  open- 
ings closed,  flues  blocked  up,  polluted  water 
supply,  foul  cisterns,  non-removal  of  house 
refuse,  and  want  of  cleanliness.  The  chief 
enactments  which  give  public  control  over 
these  matters  are  the  Public  Health  Acts,  1875 
and  1891,  The  Housing  of  the  Working  Classes 
Act,  1890,  The  London  Building  Act,  1894, 
and  the  various  bye-laws  of  the  county  and 
district  councils.  H.  A. 

Burial  Grounds  and  Cemeteries. — Sani- 
tary Requirements  of  Cemeteries — Size  of  Grave 
Spaces — Purchase  of  Land  for  Burial  Grounds — 
Power  to  Appropriate  Land  —  Disused  Burial 
Grounds — Repairs  to  Fencing  Surrounding  Burial 
Grounds. 

SANITARY  REQUIREMENTS  OF  CEMETERIES. — 
In  1888  the  Local  Government  Board  issued 
a  "  Memorandum  on  the  Sanitary  Require- 
ments of  Cemeteries."  It  embodies  the  views 
of  the  official  medical  advisers  of  the  English 
Government  as  to  avoidance  of  dangers  to 
health.  It  is  stated  that  the  soil  of  a  ceme- 
tery should  be  of  an  open  porous  nature,  with 
numerous  interstices ;  easily  worked,  yet 
not  loose ;  free  from  water  or  hard  rock  to 
a  depth  of  at  least  8  ft.,  and  sufficiently 
elevated  above  the  drainage  level  of  the 
locality.  Loam  and  sand  are  the  best ;  clay 
and  loose  stones  the  worst  soils.  It  may  be 
taken  that  a  distance  of  200  yards  is  amply 
sufficient  to  prevent  any  injury  to  health  from 
a  well-kept  cemetery,  so  far  as  regards  noxious 
matters  transmitted  through  the  air.  The 


BUR 


ENCYCLOPAEDIA  OF 


BUR 


Burial  Act  of  1855  prescribes  100  yards  as  the 
minimum  distance  between  the  burial  places 
and  human  habitations  ;  the  Cemeteries  Act, 
1847,  200  yards.  The  drainage  of  a  cemetery 
should  not  be  allowed  to  enter  a  stream  from 
which  water  is  drawn  for  domestic  use.  The 
Acts  and  regulations  prescribe  no  limit  of 
distance  for  water  supplies  within  which  a 
cemetery  is  not  to  be  established.  There  is 
no  power  to  prevent  anyone  from  sinking  a 
well  on  his  own  property,  as  near  to  a  ceme- 
tery as  he  pleases.  The  regulations  of  the 
Home  Office  prescribe  that  no  unwalled  grave 
shall  be  reopened  within  fourteen  years  after 
the  burial  of  a  person  above  twelve  years  of 
age,  or  within  eight  years  after  the  burial  of 
a  child  under  twelve  years  of  age,  unless  to 
bury  another  member  of  the  same  family, 
in  which  case  a  layer  of  earth,  not  less  than 

1  ft.  thick,   shall  be  left  undisturbed  above 
the  previously  buried  coffin  ;  but  if  on  reopen- 
ing any  grave  the  soil  be  found  to  be  offensive, 
such   soil  shall  not  be  disturbed,  and  in  no 
case  shall  human  remains  be  moved  from  the 
grave. 

SIZE  OF  GRAVE  SPACES. — The  size  of  the 
grave  spaces  is  9  ft.  by  4  f t.  =  4  square  yards, 
for  an  adult ;  and  for  a  child  under  twelve 

2  square  yards,  viz. :  either  4^  ft.  by  4  ft.  or 
6  ft.  by  3  ft.     They  allow  for  the  hole  dug  for 
an  adult  to  be  7  ft.  by  2  ft.     In  any  case  it  is 
important  that  each  grave  should  be  at  least 
a   foot   distant   from    the    nearest   grave   on 
every  side.     The  minimum  allowance  of  space 
in   a    cemetery   should   be   about   a   quarter 
of    an    acre    per    1,000    inhabitants.      This 
allows  the  graves  to  be  re-used  every  fourteen 
years. 

PURCHASE  OF  LAND  FOR  BURIAL  GROUNDS. — 
A  burial  board,  with  the  vestry  or  vestries  of 
the  parish  or  respective  parishes  for  which 
the  board  is  appointed  to  act,  may  purchase 
any  lands,  including,  if  necessary,  any  ceme- 
tery belonging  to  any  company  or  persons,  or 
in  lieu  of  providing  a  burial  ground  may 
contract  with  any  company  or  persons  entitled 
to  any  cemetery  for  the  interment  therein  of 
the  bodies  of  persons  who  would  have  had 


rights  of  interment  in  the  burial  grounds  of 
the  parish  or  parishes  for  which  the  burial 
board  acts.  No  approval,  sanction,  or  authori- 
sation of  the  vestry  is  requisite  where  the 
town  council  of  a  borough,  or  a  local  board,  or 
improvement  commissioners  have  been  con- 
stituted a  burial  board  by  Order  in  Council. 
Where  the  vestry  refuse  or  neglect  to  authorise 
the  necessary  expenditure  for  providing  a 
burial  ground  and  building  the  necessary 
chapel  or  chapels  thereon,  the  Secretary  of 
State  may  on  appeal  authorise  the  expendi- 
ture, the  borrowing  of  money  for  the  purpose, 
the  purchase  of  land,  &c.,  without  any  further 
sanction,  approval,  or  authorisation  of  the 
vestry.  A  burial  board  may  lay  out  and  em- 
bellish any  burial-ground  provided  by  them  in 
such  manner  as  may  be  fitting  and  proper, 
and  may  build  on  any  land  to  be  pur- 
chased or  appropriated,  according  to  plans 
approved  by  the  Bishop  of  the  Diocese,  a 
chapel  for  the  performance  of  the  burial 
service  according  to  the  rites  of  the  Church 
of  England. 

POWER  TO  APPROPRIATE  LAND.  —  A  Town 
Council  of  any  borough  may  appropriate  for 
the  purposes  of  the  Burial  Acts  any  land  be- 
longing to  the  body  corporate  of  the  borough,  or 
vested  in  any  trustees,  or  others  for  the  general 
use  of  the  borough,  or  for  any  specific  charity, 
provided  that  when  any  land  so  appropriated 
is  subject  to  any  charitable  use  it  may  be  taken 
only  on  such  conditions  as  the  Chancery  Divi- 
sion in  the  exercise  of  its  jurisdiction  over 
charitable  trusts  shall  direct  and  appoint. 

DISUSED  BURIAL  GROUNDS. — It  is  not  lawful 
to  build  upon  any  disused  burial  ground,  ex- 
cept for  the  purpose  of  enlarging  a  church, 
chapel,  meeting-house,  or  other  places  of 
worship. 

KEPAIRS  TO  FENCES  SURROUNDING  BURIAL 
GROUNDS. — Any  urban  authority  constituting 
a  burial  board  may  from  time  to  time  repair 
and  uphold  the  fences  surrounding  any  burial 
ground  which  has  been  discontinued  as  such 
within  their  jurisdiction,  or  they  may  take 
down  any  fences  and  substitute  others  in  lieu 
thereof.  "  A.  C.  F. 


64 


CAL 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


CAM 


Calorifier.  —  A  chamber  having  tubes 
through  which  steam  is  projected  for  the  pur- 
pose of  heating  the  surrounding  water. 

Camp  Sanitation.  —  Camp  Site  —  Camp 
Space — Water  Supply — Kitchens  and  Ablution 
Places — Disposal  of  Excreta. — All  camps  may  be 
regarded  as  hastily  constructed  towns,  in  which 
the  tents  or  huts  represent  so  many  houses, 
while  their  sanitation  depends  upon  orderly 
habits  governed  by  corporate  and  individual 
discipline.  The  selection  of  a  camp  site  is 
dominated  largely  by  the  facilities  which  exist 
for  obtaining  water.  This  is  particularly  so 
in  regard  to  temporary  encampments,  but 
where  camp  sites  are  likely  to  be  occupied  any 
length  of  time  the  feasibility  of  bringing  the 
water  to  the  camp  must  be  as  much  considered 
as  taking  the  camp  to  the  water. 

THE  CAMP  SITE. — The  proper  location  of  a 
camp,  as  a  matter  of  importance  in  maintain- 
ing the  health  of  the  occupants,  demands  in- 
telligent consideration.  It  is  a  good  rule  to 
select  the  site  as  if  for  continual  occupancy, 
and,  if  possible,  on  high  ground,  since  not  only 
is  the  surface  drainage  better,  but  exposure  to 
air  currents  facilitates  evaporation.  Situations 
at  the  base  of  hills  are  usually  damp,  and  only 
acceptable  if  a  deep  transverse  ravine  inter- 
cepts the  drainage  from  the  adjacent  high 
ground.  No  encampment  should  be  placed  in 
ravines  or  dry  beds  of  water-courses ;  simi- 
larly valleys  and  punch-bowl  depressions  are 
objectionable.  The  vicinity  of  marshes  or 
irrigated  lands  should  be  avoided,  while  locali- 
ties to  which  surface  or  subsoil  water  gravi- 
tates are  undesirable  for  obvious  reasons. 
An  abandoned  camp  site  should  never  be 
utilised  except  under  circumstances  of  great 
necessity — soil  contamination  is  certain,  and 
there  is  a  strong  probability  of  its  specific 
infection.  As  regards  actual  soil,  it  may  be 
said  the  more  porous  the  better ;  but  if  a  camp 
must  be  located  upon  an  impermeable  soil,  the 
area  affording  the  best  surface  drainage  and 
the  least  dust  should  be  chosen.  Apart  from 
the  accessibility  to  water,  the  golden  rule  in 
the  selection  of  camp  sites  is — choose  areas 

M.S.E. 


which  are  not  only  dry,  but  clean,  that  is,  have 
not  been  occupied  recently  for  other  encamp- 
ments, and  are  not  fouled  or  in  any  way 
encumbered  with  the  recent  filth  of  man  and 
animals. 

THE  CAMP  SPACE. — Owing  to  physical  diffi- 
culties connected  with  the  locality,  this  is 
subject  to  variation,  but  the  main  principle  to 
be  borne  in  mind  is  that  each  tent  or  hut 
should  be  separated  from  its  neighbour  by  an 
interval  equal  to  its  own  height.  The  risk  of 
camp  life,  however,  lies  not  so  much  in  ex- 
cessive density  of  population  on  the  gross 
superficies  as  in  overcrowding  of  individual 
tents  or  huts.  This  is  a  matter  of  great  diffi- 
culty, and  often  dependent  upon  financial  con- 
siderations. So  far  as  possible,  each  occupant 
of  a  tent  or  hut  should  be  allotted  an  available 
space  of  20  square  feet  in  order  to  minimise  the 
facilities  for  direct  infection  from  man  to  man 
which  camp  life  does  so  much  to  foster.  All 
tent  walls  should  be  looped  up  daily  for  at 
least  three  hours,  and  during  the  absence  of 
the  occupants,  so  that  the  tent  area  may  be 
disinfected  by  fresh  air  and  sunlight.  Where 
huts  are  used  the  doors  and  windows  must  be 
opened  daily  to  permit  of  aeration.  In  perma- 
nent camps  all  tents  should  be  struck  and 
their  enclosed  ground  area  sunned  or  aired  for 
eight  hours  every  week  ;  if  the  space  permits 
the  tents  should  be  shifted  to  a  new  site  once 
a  month.  The  excavating  of  soil  within  a  tent 
area  should  be  forbidden  as  tending  to  impede 
ventilation  and  cleanliness.  If  floor-boards  are 
not  available  the  ground  inside  tents  may  be 
covered  with  straw  or  tarpaulin,  but  whatever 
is  employed  it  must  be  turned  out,  aired  and 
cleaned  daily  so  long  as  weather  permits. 
Blankets  and  bedding  must  be  sunned  and 
aired  each  day.  Whenever  possible,  special 
accommodation  should  be  provided  in  all 
camps  for  the  eating  of  meals  and  the  storage 
of  food.  The  eating,  storage  or  retention  of 
food  in  the  living  tents  or  huts  must  be  dis- 
couraged, as  the  facilities  for  contamination  in 
these  crowded  places  are  great.  If  food  must 
be  retained  or  stored,  every  endeavour  must 
be  made  to  keep  it  in  closed  tins  or  boxes  so 
65  if 


CAM 


ENCYCLOPAEDIA  OF 


CAM 


that  flies  may  not  gain  access  to  it.  All  food 
remains,  particularly  if  not  likely  to  be  utilised 
in  a  few  hours,  should  be  either  burnt  or 
buried. 

WATER  SUPPLY. — The  general  principles 
affecting  this  question  need  not  be  con- 
sidered here  except  to  emphasise  the  need  of 
scrupulously  safeguarding  the  sources  of 
supply  from  casual  contamination  by  men  or 
animals.  When  the  circumstances  permit, 
water  for  animals  should  be  taken  at  a  point 
distinct  from  that  supplying  men  ;  in  the  case 
of  running  water  the  animal's  drinking  place 
must  be  below  that  whence  the  water  for  men 
is  taken.  In  camps  water  is  either  available 
from  some  stand-pipes  or  from  natural  source 
of  supply.  In  each  case  it  is  distributed  by 
tanks  on  wheels  or  other  vessels  such  as  pails, 
canvas  tanks,  barrels,  or  cans.  If  water  is 
stored  in  camp  the  vessels  must  be  protected 
from  dust  and  other  contamination  by  suitable 
covers.  Individuals  should  not  be  allowed  to 
drink  direct  from  the  taps  of  water-tanks,  or 
from  the  rims  or  spouts  or  other  receptacles 
used  for  carrying  or  distributing  water. 

KITCHENS  AND  ABLUTION  PLACES. — The  cook- 
ing of  food  in  camps  presents  no  serious  sani- 
tary problems — at  best  it  must  be  crude  and 
rough.  The  most  important  details  which 
need  attention  are:— (1)  That  kitchens  be 
located  well  away  from  latrines,  urine  pits, 
or  other  receptacles  for  refuse  and  garbage. 
(2)  All  sullage  water  must  be  made  to  pass 
into  pits  from  which  it  can  drain  away  along 
suitably  dug  trenches.  This  waste  water  is 
greasy  and,  if  allowed  to  pass  direct  on  to  soil, 
soon  makes  a  felt-like  scum  which  attracts 
flies.  A  useful  procedure  is  to  fill  the  recep- 
tion pits  or  the  upper  ends  of  the  drainage 
channels  with  grass  or  coarse  brushwood.  If 
the  greasy  water  be  poured  on  to  this  material 
the  grease  and  other  solids  are  entangled, 
allowing  the  clearer  liquid  to  run  freely  away. 
The  grass,  or  brushwood,  loaded  with  fatty 
matter,  is  conveniently  burnt  daily  and  re- 
placed by  fresh  cuttings.  In  all  camps  the 
system  of  washing  up  cooking  utensils  needs 
careful  supervision,  a  separate  washing-up 


place  being  allocated  for  this  purpose.  This 
should  be  provided  with  as  much  boiled  or 
filtered  water  as  circumstances  permit.  If 
sand  is  used  for  cleaning  vessels  this  should 
be  previously  baked  over  a  fire.  The  whole 
process  of  washing  up  and  sand-baking  should 
be  under  the  supervision  of  a  sanitary  orderly. 
The  ablution  places  need  to  be  located  con- 
veniently near  the  tents  or  huts,  and  the  soiled 
and  soapy  water  therefrom  drained  away  and 
disposed  of  on  similar  principles  to  those  in- 
dicated for  kitchen  sullage  water.  In  standing 
camps,  unless  the  physical  conditions  of  the 
soil  and  the  gradients  are  distinctly  favourable 
for  a  rapid  absorption  and  soaking  away  of  all 
sullage  and  ablution  water,  it  will  be  advisable 
either  to  shift  the  location  of  the  kitchen  and 
washing  places  every  few  days  or  to  collect  this 
liquid  in  air-and-water- tight  receptacles.  Such 
receptacles  should  be  placed  on  raised  plat- 
forms for  the  better  protection  of  themselves 
and  the  ground  beneath  them,  and  should  be 
emptied  daily  and  the  contents  disposed  of 
outside  the  camp  area.  Before  being  returned 
to  use  they  should  be  cleaned  and  smeared 
over  with  a  cloth  soaked  in  crude  creosote  oil. 
DISPOSAL  OF  REFUSE. — Kitchen  refuse  and 
the  various  other  items  which  go  to  make  up 
the  ordinary  refuse  from  camps  should  never 
be  thrown  upon  casual  ground,  but  placed  in- 
variably in  special  receptacles  conveniently 
located  for  the  purpose.  In  temporary 
camps  these  receptacles  best  take  the  form 
of  pits,  but  where  these  are  employed  the 
contents  must  be  covered  over  each  day 
with  at  least  6  in.  of  fine  earth,  the  constant 
endeavour  being  to  protect  the  material 
from  flies.  In  more  permanent  camps  all  this 
garbage  and  refuse  should  be  placed  in  closed 
metal  receptacles,  the  contents  of  which  must 
be  removed  and  disposed  of  daily.  On  no 
account,  unless  necessity  compels,  should  the 
solid  and  liquid  refuse  be  mixed.  Carts  or 
vehicles  for  the  removal  of  refuse  to  the  place 
of  disposal  should  be  of  special  design  and 
capable  of  preventing  any  escape  of  their  con- 
tents. The  final  disposal  of  this  material  is 
often  a  matter  of  difficulty.  The  location  of 


66 


CAM 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


CAM 


the  place  should  be  always  outside  the  camp 
area  and  placed  to  leeward  of  prevailing  winds, 
and  remote  from  the  kitchens  and  source  of 
water  supply.  There  are  two  possible  methods 
of  disposal — burial  or  burning.  The  former 
is  suitable  where  the  amount  of  material  is  not 
excessive,  but  when  much  refuse  is  present 
the  labour  necessary  to  dig  sufficiently  large 
pits  is  prohibitive.  In  these  cases  destruction 
by  fire  is  the  only  means  of  disposal ;  in  fact, 
it  may  be  said  that  burning  is  the  ideal  mode 
of  disposal  in  all  cases.  Theoretically  this  is 
so,  but  practically  it  is  difficult  to  carry  out, 
mainly  on  account  of  the  natural  dampness  of 
the  material.  Various  portable  destructors 
have  been  proposed  and  used,  probably  the 
best  for  fixed  encampments  is  that  of  Horsfall. 
In  the  absence  of  special  destructors  much  can 
be  done  by  means  of  improvised  crematories. 
When  crude  mineral  oil  is  available  its  incor- 
poration with  the  material  constitutes  an 
effective  aid  to  its  combustion.  The  construc- 
tion of  a  simple  grate  by  laying  iron  rods  or 
railway  rails  so  as  to  form  a  grid  or  platform, 
on  lateral  supports  built  up  of  sods  or  bricks 
is  successful  in  the  combustion  of  camp 
refuse — its  utility  is  enhanced  if  a  series  be 
built,  arranged  concentrically  round  a  central 
cone  of  rails  or  rods  stacked  or  bound  together. 
Cremators  of  this  kind  can  be  built  of  any 
size  at  little  cost.  One  measuring  10  ft.  in 
diameter  is  capable  of  burning  two  tons  of 
damp  refuse  daily,  and,  if  care  be  exercised,  on 
to  the  burning  mass  the  contents  of  latrine 
buckets  can  be  thrown  and  incinerated  without 
local  offence.  On  the  same  principle  a  similar 
crematory  can  be  constructed  by  lining  a 
circular  shallow  pit,  say  3  ft.  deep  and  12  ft. 
in  diameter,  with  large  stones,  and  heaping 
other  stones  in  the  centre  to  form  a  pyramid 
to  a  height  of  6  ft.  If  ordinary  wood  be 
used  to  start  the  fire,  a  freely  burning  furnace 
can  be  maintained  by  judicious  feeding  with 
refuse.  Its  stones  soon  become  intensely  hot, 
and  serve  to  dispose  of  liquid  and  damp 
material  with  rapidity.  In  any  devices  of  this 
kind  the  great  essential  is  to  secure  a  draught 
of  air  under  and  through  the  material  to  be 


burnt,  and  the  damper  the  mass  the  greater  the 
need  of  air.  An  improvised  refuse  destructor 
of  a  simple  nature  can  be  made  by  digging 
two  trenches  intersecting  at  right  angles  ;  each 
trench  should  be  9  in.  deep,  and  any  length 
from  5  ft.  Over  the  angle  of  intersection  a 
shaft  is  built  up  of  sods,  a  few  pieces  of  iron 
hooping,  or  other  resistant  material,  supporting 
the  shaft  where  it  crosses  the  trenches.  A  fire 
can  be  quickly  lighted  at  the  base  of  the 
chimney  and  fed  steadily  by  throwing  rubbish 
down  the  shaft.  Assuming  the  refuse  be 
added  with  ordinary  care  and  the  potency  of 
the  draught  trenches  maintained  by  judicious 
raking,  an  enormous  amount  of  combustible 
material  can  be  disposed  of  in  a  few  hours. 
Modifications  of  this  type  will  naturally  suggest 
themselves. 

DISPOSAL  OF  EXCRETA. — This  question  is 
vital  to  the  sanitary  interests  of  all,  but  pro- 
vided ordinary  intelligence  be  exercised,  it 
presents  fewer  difficulties  than  might  be 
expected.  The  general  location  of  latrines 
will  depend  upon  the  direction  of  the  prevail- 
ing wind  and  the  position  of  the  water  supply, 
the  rule  to  be  observed  being  to  leeward  of 
the  camp  and  in  such  a  position  that  no 
possible  fouling  of  the  water  supply  can 
result.  The  construction  of  these  places 
must  not  be  delayed  until  tents  or  huts  are 
fixed,  but  completed  as  soon  as  possible,  to 
safeguard  casual  fouling  of  the  camp  area  and 
its  vicinity.  Under  ordinary  circumstances, 
latrines  may  be  put  100  yards  distant  from 
the  tents  or  huts,  but  always  as  far  as  possible 
away  from  the  kitchens  and  other  places 
where  food  is  prepared  or  stored.  The  extent 
and  type  of  latrine  accommodation  in  camps 
will  vary  according  to  whether  the  area  is  for 
temporary  or  permanent  occupation.  For 
temporary  camps  the  allowance  should  be 
5  %,  and  in  those  intended  for  long  occupa- 
tion at  least  8  %.  These  figures  may  be  taken 
to  represent  either  yards  or  seats,  according 
to  circumstances.  The  multiplication  of 
latrines  is  undesirable,  as  one  or  two  fairly 
large  ones  are  easier  of  control  than  several 
smaller  ones,  and  soil  pollution  is  also  more 
67  F  2 


CAM 


ENCYCLOPAEDIA  OF 


CAN 


localised.  In  permanent  camps,  latrine 
accommodation  will  best  take  the  form  of 
pail-middens  with  dry  earth,  fitted  with 
rough  wooden  seats.  For  the  reception  of 
urine,  iron  tubs  should  be  provided,  these 
being  placed  adjacent  to  the  ordinary  latrines 
for  day  use,  and  during  the  night  at  selected 
points  convenient  for  the  tents.  The  contents 
of  these  several  receptacles  will  need  daily 
removal  in  covered  and  water-tight  carts  to 
points  well  away  from  the  camp  area,  to  be 
disposed  of  by  burial  in  the  earth.  If  portable 
middens,  such  as  pails,  are  not  provided,  then 
the  seats  must  be  placed  over  pits  or  trenches 
specially  dug.  "Whatever  form  the  latrine 
takes,  its  successful  conduction  depends  abso- 
lutely upon  rigid  adherence  to  the  rule  that 
the  excreta  must  be  quickly  and  completely 
covered  over  with  earth,  and  this  depends, 
again,  upon  the  enforcement  of  individual 
sanitary  discipline,  adequate  personnel,  and 
competent  administrative  control  and  super- 
vision. For  ordinary  or  more  or  less  tempo- 
rary camps,  the  usual  latrine  is  a  trench, 
provided  or  not  with  a  seat.  Some  20  ft.  of 
trench,  2  ft.  deep  and  16  in.  wide,  is  the 
common  allowance  for  each  hundred  persons. 
For  temporary  encampments  and  where  the 
provision  of  a  rough  seat  is  impossible,  a 
preferable  arrangement  is  to  provide  a  series 
of  short  trenches  in  parallel,  across  which  the 
user  straddles ;  each  trench  should  be  3  ft. 
long,  1  ft.  wide  and  2  ft.  deep,  with  the 
interspace  between  each  trench  not  more  than 
2£  ft.,  preferably  less  if  the  soil  permits,  so 
as  to  preclude  use  otherwise  than  in  the 
straddling  attitude.  Every  latrine  needs  to 
be  surrounded  by  some  form  of  screen,  also 
roofed  in  if  possible,  and  the  soil  removed 
from  the  trenches  must  be  broken  up  and 
carefully  piled  to  the  rear,  whence  it  can  be 
scattered  as  needed  over  the  deposits.  All 
displaced  grass  sods,  too,  should  be  carefully 
stacked  in  rear  of  the  loose  earth,  so  that 
when  the  trench  is  filled  in  these  grass  sods 
can  be  replaced  and  the  soiled  area  made 
neat  and  wholesome.  In  wet  weather,  latrines 
should  be  protected  by  a  shallow  drain  to 


prevent  ingress  of  surface  water.  So  soon  as 
the  contents  of  the  trench  reach  within  6  in. 
of  the  top,  it  should  be  filled  in,  the  turf 
replaced  and  new  ground  taken  up  by  digging 
fresh  trenches.  Some  kind  of  implement, 
such  as  a  spade,  scoop,  or  tin  should  be  by 
each  trench  for  replacing  earth  at  each  time 
of  use.  Kicking  the  soil  in  by  the  foot  is 
certain  to  be  a  failure  and  should  be  dis- 
couraged as  conducive  to  imperfect  covering 
of  the  excreta  and  consequent  slackness. 
Notices  should  be  displayed  prominently 
within  all  latrines  impressing  upon  users 
the  necessity  of  covering  their  dejecta  before 
leaving  with  earth.  Failure  on  their  part  to 
adequately  cover  their  excreta  should  be  made 
a  matter  of  discipline  and  entail  some  punish- 
ment or  disability.  If  difficulty  is  experienced 
in  getting  this  essential  act  properly  carried 
out,  an  alternative  is  to  place  a  man  within 
the  screen,  provided  with  a  spade,  and  direct 
him  to  cover  each  deposit  with  earth  as  each 
depositor  moves  off.  A  tour  of  such  duty 
should  not  exceed  two  hours,  and  might  well 
be  limited  to  one  hour.  A  modification  of 
this  disciplinary  method  is  to  place  a  sanitary 
patrol  or  policeman  over  the  latrine  to  see 
that  each  user  thereof  fulfils  his  duty  to 
himself  and  his  neighbour.  So  long  as  the 
sanitary  foresight  of  the  masses  remains  at 
the  present  low  level,  the  latrine  sentry,  how- 
ever great  the  sentimental  objections  may 
appear,  is  a  necessity,  and  the  only  safeguard 
against  fsecal  diseases  which  spread  in  camps 
from  this  point.  The  care  and  conduct  of 
latrines  in  camps  must  be  ever  regarded  as  a 
disciplinary  matter,  and  unless  it  is  so 
regarded  these  places  will  be  the  foci  of  disease 
in  all  climates.  Consistent  practice  on  the 
lines  explained  will  result  in  the  latrine  being 
no  more  offensive  than  the  ordinary  ablution 
place.  When  this  is  so,  the  incidence  of 
filth-originated  or  dust  and  fly-borne  disease 
in  camps  can  be  reduced  to  a  minimum. 

K  H.  F. 


Candy      Mechanical      Filter. 

"MECHANICAL   FILTRATION.") 


(See 


68 


CAN 


MUNICIPAL   AND   SANITAEY   ENGINEERING. 


GEM 


Candy  Settling  Tank.  —  This  consists 
of  a  flat-bottomed  sewage  precipitating 
tank  in  which  the  upward-flow  principle  has 
been  applied,  and  which  admits  of  the  sludge 
being  removed  by  the  hydrostatic  head  of 
water  within  the  tank,  the  sludge-pipe  rising 
to  a  level  18  in.  below  the  tank  top-water 
level.  The  sludge  is  removed  by  a  revolving 
perforated  sludge-pipe  pivoted  at  the  centre  of 
the  tank  floor.  This,  together  with  a  rubber 
squeegee  passing  over  the  floor  and  a  similar 
vertical  squeegee  for  the  walls  of  the  tank, 
is  worked  by  means  of  a  worm-gear  at 
the  ground  surface  level.  Hard  substances 
are  apt  to  jam  between  the  squeegee  and 
the  floor  of  the  tank,  but  if  the  sludge 
is  removed  daily  the  tank  on  the  whole 
works  well,  and  the  growths  of  bacteria 
and  deposit  of  sludge  on  the  sides,  which 
cause  trouble  in  the  Dortmund  tank,  are 
prevented  by  regularly  working  the  revolving 
squeegees. 


Carbolic  Acid,  or  phenol,  C6H5OH,  is  a 
colourless  crystalline  solid,  very  hygroscopic, 
and  having  a  characteristic  odour.  It 
melts  at  42°  C.,  boils  at  182°  C.,  and  has 
a  specific  gravity  of  1'084  at  0°  C.  It  is 
not  very  soluble  in  water,  a  saturated 
solution  at  15°  C.  containing  about  5  %, 
but  phenol  itself  dissolves  water,  taking 
up  nearly  one-fourth  its  weight  at  15°  C., 
forming  an  oily  liquid.  The  liquefied 
phenol  of  the  B.P.  consists  of  100  parts 
of  carbolic  acid  with  10  parts  of  water 
by  wreight.  It  has  a  caustic  action  on 
the  skin  and  mucous  membrane. 

Carbolic  acid  is  produced  during  the 
decomposition  of  a  variety  of  substances  ; 
practically  all  the  phenol  of  commerce  is 
obtained  from  the  distillation  of  coal.  Com- 
mercial carbolic  acid  is  a  dark  oily  liquid 
containing  higher  homologues  and  not  miscible 
with  water,  and  requires  some  500  times  its 
volume  to  dissolve  it.  Until  recently  it  has 
been  widely  employed  for  the  preparation  of 
disinfectant  fluids  and  powders,  and  has  the 
merit  of  showing  no  great  diminution  of 


germicidal  activity  in  the  presence  of 
organic  matter  either  in  solution  or  in 
suspension.  Absolute  phenol  has  been  adopted 
as  a  standard  germicide  for  the  testing  of 
disinfectants.  (See  "  DISINFECTION.") 

Catch  Pits,  —  Depressions,  hollows  or 
sump  holes  made  use  of  in  drainage  and 
sewage  disposal  works  for  arresting  sand  and 
other  such  detritus  which  may  pass  through 
drains.  The  matter  to  be  detained  sinks  to 
the  bottom  of  the  pits  by  gravitation,  while 
the  liquid  and  lighter  solids  of  the  sewage 
pass  out  through  the  overflow. 

Catchment  Area. — (See  "  WATER-SHED  " 
and  "  WATER  SUPPLY.") 

Catchwater  Drain.  —  Open  ditches  or 
catchwater  drains  are  artificially  cut  along 
the  contour  lines  of  hillside  slopes  for  the 
purpose  of  intercepting  the  flow  from  rainfall 
and  preventing  damage  which  would  other- 
wise be  caused  by  the  water  rushing  to  the 
foot  of  the  hill-side.  The  wrater  thus  inter- 


Catchwater  Drain. 

cepted  is  passed  down  from  one  catchwater 
drain  to  another  by  means  of  properly  con- 
structed conduits  of  masonry,  brickwork,  or 
piping,  and  so  safely  conveyed  to  the  required 
point  of  discharge. 

Cement,  Portland. — Portland  cement  is 
so  called  from  its  resemblance  to  Portland 
stone.  It  is  an  artificial  cement  composed 


69 


CEM 


ENCYCLOPAEDIA  OF 


CES 


K  -  -  1-75*  -    - 


of  various  ingredients  intimately  mixed, 
calcined  and  ground,  finally  consisting  of 
about  33%  clay,  63%  lime,  3%  iron,  mag- 
nesia, &c. ;  the  clay  (silicate  of  alumina) 
confers  the  property  of  hydraulicity.  The 
materials  used  are  chalk  and  clay  by  the  wet 
process,  and  limestone  and  clay,  or  shale,  by 
the  dry  process  ;  the  wet  process  is  usually 
employed  on  the  Thames  and  Medway.  The 
approximate  proportions  are  1  of  clay  to  3 
of  white  chalk  or  4  of  grey  chalk ;  the  quality 
depends  upon  the  care  taken  in  the  manu- 
facture. Under-burning  produces  a  greater 
bulk  from  a  given  quantity  of  material,  and 

the  specific  gravity  is 
thereby  reduced ;  less 
fuel  and  grinding  are 
required,  and  a  quick 
setting  cement  is  pro- 
duced, but  it  never 
reaches  the  same 
strength  as  if  better 
burnt.  The  heavy 
cements  are  always 
slower  in  setting,  but 
have  greater  ulti- 
mate tensile  strength. 
Light  cements  may 
be  used  for  rendering,  but  a  fairly  heavy 
cement  is  necessary  for  all  work  of  importance. 
Over- burnt  cement  is  slow  and  irregular  in 
setting.  Cement  which  is  over-limed  expands 
in  setting,  that  which  is  over-clayed  contracts. 
The  setting  of  Portland  cement  is  due  to  the 
crystallisation  of  a  compound  silicate  of  lime 
and  alumina,  together  with  the  evaporation 
of  surplus  moisture,  and  in  course  of  time 
the  formation  of  a  small  amount  of  car- 
bonate of  lime  by  absorption  of  carbon 
dioxide  from  the  atmosphere.  The  specifi- 
cation of  weight  by  Imperial  striked  bushel 
is  now  obsolete,  and  a  specific  gravity  of 
3'1  is  required  instead,  taken  with  a  specific 
gravity  bottle.  Of  late  years  cement  has  been 
ground  much  finer  than  formerly,  giving  it 
more  covering  power  and  enabling  it  to  take  a 
larger  quantity  of  sand,  or,  conversely,  reach 
a  higher  strength.  The  residue  on  a  sieve 


Standard  Briquette  for 
Testing  Portland 
Cement. 


70 


180  X  180  =  32,400  meshes  per  sq.  in.  must 
not  exceed  12  %.  The  British  Standard  Speci- 
fication for  Portland  Cement  revised  to  June, 
1907,  is  generally  adopted.  Figure  shows  the 
dimensions  of  a  standard  briquette.  The 
tensile  tests  on  briquettes  1  sq.  in.  net  section 
are,  7  days  from  gauging  400  Ibs.,  28  days 
500  Ibs.  If  the  7-day  test  comes  out  higher 
than  400  Ibs.,  there  shall  be  an  increase 
over  500  Ibs.  at  28  days,  varying  from 
25%  down  to  5%.  Three  grades  of  cement 
are  recognised  —  "quick-setting,"  in  which 
the  final  setting  time  is  not  less  than  10 
nor  more  than  30  minutes;  "medium- 
setting,"  in  which  the  time  is  not  less 
than  £  hour  nor  more  than  1  hour ;  "  slow- 
setting,"  in  which  the  time  is  not  less  than 
2  hours  nor  more  than  7  hours.  Final 
setting  occurs  when  the  Yicat  needle  fails 
to  make  an  impression.  The  Le  Chatelier 
test  for  expansion  is  considered  to  be  of  great 
importance.  Accelerated  or  boiling  tests  are 
frequently  adopted  to  ascertain  the  soundness 
of  cement.  H.  A. 

Cemeteries.— (See  "  BURIAL  GROUNDS  AND 
CEMETERIES.") 

Cesspool,   Self  -  Emptying    Septic.  - 

Forms  of  self-discharging  septic-tank  cess- 
pools are  being  largely  used  both  in  urban 
and  rural  districts  of  France.  These  are 
improvements  introduced  respectively  by 
Bezault  and  Degoux  on  the  old  Mouras 
siphonage  cesspool.  The  Bezault  type  con- 
sists of  an  air-tight  cesspit,  divided  into  two 
unequal  sized  chambers  by  a  vertical  partition 
reaching  nearly  to  the  ceiling,  and  perforated 
towards  the  base.  The  soil  and  rain-water 
pipes  enter  the  larger  section  of  the  tank 
vertically,  but  with  horizontal  outlets  to 
prevent  any  violent  commotion  on  the  intro- 
duction of  fresh  matter.  The  discharge  pipe 
enters  the  smaller  compartment  horizontally, 
but  has  the  end  turned  downwards,  and  at 
the  elbow  there  is  a  small  ventilation  outlet. 
The  sewage  is  collected  in  the  larger  section, 
where  it  undergoes  liquefaction  as  the  result 


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MUNICIPAL  AND   SANITAEY  ENGINEEEING. 


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of  aerobic  bacterial  activity,  air  being  intro- 
duced whenever  any  material  enters  the 
cesspool.  The  liquefied  and  drained  sewage 
enters  the  smaller  section,  and  as  soon  as 
the  liquid  reaches  the  level  of  the  horizontal 
discharge  pipe  siphonage  takes  place,  and 
any  accumulation  of  gas  generated  during 
bacterial  action  is  removed  by  way  of  the 
ventilating  orifice  with  the  flow  of  the  effluent. 
As  a  rule  the  purification  is  not  carried  very 
far  in  such  a  cesspool,  but  the  effluent  is 
entirely  free  from  flocculent  matter,  is  prac- 
tically odourless,  and  in  a  fit  condition  for 
distribution  over  a  contact  bed  or  for  broad 
irrigation.  It  is  impossible  for  any  nuisance 
from  sewer-gas  to  arise.  In  the  Degoux  type 
there  are  also  two  compartments.  The  first 
is  a  water-tight  pit,  into  which  the  soil  pipe 
discharges  vertically.  The  discharge  pipe  is 
horizontal,  with  end  bent  downwards,  the 
orifice  being  protected  by  a  grid  or  other 
contrivance  to  prevent  the  aspiration  of  paper 
or  solid  matter  during  discharge  by  siphonage. 
This  pipe  communicates  with  the  top  part  of 
the  second  water-tight  tank,  which  contains 
a  bacterial  contact  bed,  composed  of  three 
or  more  layers  of  slag  broken  up  into  different 
sizes,  resting  on  a  perforated  plate,  placed  a 
few  inches  above  the  base  of  the  tank.  Over 
the  filter  is  an  air-inlet  pipe.  The  effluent 
is  discharged  through  a  large  valve  at  the 
base,  and  this  discharge  pipe  is  provided  with 
a  small  ventilating  shaft,  fitted  with  a  vaned 
cowl,  the  shaft  being  carried  up  above  the 
eaves  of  a  house,  or  to  a  sufficient  elevation 
to  avoid  the  causing  of  any  possible  nuisance. 
The  discharge  of  effluent  is  sufficiently  rapid 
to  ensure  the  necessary  supply  of  air  to  the 
contact  bed  and  the  dispersal  of  sewer-gas. 
The  effluent,  which  is  slightly  opalescent,  is 
inodourous  and  claimed  to  be  imputrescible, 
but  sanitary  engineers  object  to  its  being 
discharged  into  any  stream  before  refiltra- 
tion  upon  beds  or  land.  The  Degoux  type  has 
been  employed  successfully  in  connection  not 
only  with  dwelling-houses  and  factories,  but 
also  for  the  collective  treatment  of  sewage  from 
houses  and  cottages  on  estates  and  from  villages. 


Cesspools. — Now  out  of  date,  yet,  fre- 
quently made  use  of,  and  permissible  if 
properly  constructed  and  placed.  Cesspools 
may  be  simply  sunk  in  a  porous  soil,  such  as 
chalk  or  gravel,  and  lined  with  loose  brick- 
work. In  this  case  the  sewage  merely  soaks 
away  when  liquefied.  At  a  safe  distance  from 
dwellings  and  sources  of  water  supply,  there  is 
no  objection  to  this  type  of  cesspool.  Other 
cesspools,  which  are  preferable,  are  those 
which  are  made  water-tight  and  from  which 
an  overflow  pipe  conveys  the  liquid  sewage  to 
some  convenient  and  safe  spot  for  ultimate 
disposal,  which  may  take  the  form  of  land 
irrigation  or  treatment  on  suitable  bacteria 
beds.  Many  such  cesspools  which  in  former 
years  were  blindly  constructed  on  right 
principles  are  in  existence,  and  have  proved 
satisfactory  even  though  their  very  position 
had  been  forgotten.  The  essentials  in  cess- 
pools are  a  suitable  capacity,  and  placing  the 
inlet  and  outlet  pipes  so  that  sewage  entering 
•the  cesspool  is  immersed,  and  the  outflow 
quite  liquid.  When,  as  is  frequently  the  case, 
the  inlet  and  outlet  are  placed  at  the  same 
level,  the  sewage  merely  passes  from  one 
to  the  other,  thus  leading  to  blockage  and 
nuisance.  If  both  are  dipped  to  about  the 
centre  of  the  contents  of  the  cesspool  the 
heavier  solids  fall  to  the  bottom  while  the 
lighter  float  on  the  surface,  and  only  liquid  is 
allowed  to  escape.  In  time  the  solids  liquefy 
by  bacterial  action  and  are  displaced  by  fresh 
solids.  A  cesspool  so  constructed  closely 
resembles  a  "  Septic  Tank  "as  to  which  see 
"  SEWAGE  DISPOSAL." 

Chimney  Shafts. — Tall  chimney  shafts, 
as  used  for  factories  and  engineering  works 
generally,  are  usually  built  of  brickwork,  but 
more  recently  iron  and  reinforced  concrete 
have  also  largely  come  into  use.  Perforated 
radiated  bricks  are  employed  in  the  Alphons 
Custodis  system  of  construction,  which  also 
has  been  largely  used  in  this  country  of  late 
years.  These  shafts  are  of  thinner  outer  walls 
than  the  ordinary  recognised  English  mode  of 
construction,  and  are  consequently  of  less 


71 


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weight  and  cheaper  to  build.  The  usual 
practice  in  this  country  is  shortly  as  follows  : — 
the  brickwork  to  be  not  less  than  9  in.  thick 
at  the  top  and  for  20  ft.  below,  to  be  increased 
4J  in.  in  thickness  for  every  additional  20  ft. 
of  height  measured  downwards.  The  batter 
to  be  2^  in.  in  every  10  ft.,  or  an  inclination  of 
1  in  48.  In  circular  shafts  the  outside  width 
or  diameter  at  the  base  to  be  -^th  of  the  total 
height,  and  in  square  shafts  to  be  not  less  than 
Y^th  of  the  total  height.  No  cornice  or  other 
projection  should  stand  out  more'  than  the 
thickness  of  the  brickwork  at  the  top.  The 
firebrick  lining  is  to  be  additional  to  the 
thicknesses  of  the  ordinary  brickwork  as  pre- 
scribed by  the  above-named  rules.  This 
lining  should  not  be  bonded  in  with  the 
brickwork  of  the  outer  walls,  but  be  built  quite 
free  in  order  that  it  may  expand  and  contract 
without  affecting  the  outer  walls.  The  height 
to  which  this  lining  should  be  carried  up 
depends  upon  the  heat  of  the  gases  and  the 
fluctuations  of  temperature  within  the  shaft. 
Usually,  in  a  shaft  150  ft.  high  the  firebrick 
lining  may  be  advantageously  carried  up  to 
about  70  ft. :  from  the  bottom  of  the  inlet  flue 
at  the  base.  The  top  of  the  shaft  may  be 
provided  with  a  cast-iron  cap,  which  is 
preferable  to  stone,  as  the  latter  is  very  liable 
to  deteriorate,  especially  when  held  together 
with  iron  cramps.  Cramps,  if  used,  should  be 
of  gun-metal,  and  continuous  gun-metal  rings 
are  sometimes  adopted  in  circular  shafts  to 
bind  the  stone  courses  in  chimney  caps. 
Special  care  should  be  taken  to  see  that  the  shaft 
stands  upon  a  thoroughly  sound  foundation. 
It  is  usual  to  provide  an  extended  base  of 
Portland  cement  concrete  from  3  to  10  ft. 
thick,  according  to  the  necessities  of  the  site, 
in  order  to  thoroughly  distribute  the  weight 
of  the  shaft  over  a  large  area.  The  brickwork 
foundation  is  then  commenced  upon  this  and 
gradually  tapered  up  to  the  proper  size  or 
outside  diameter  of  shaft  at  the  finished 
ground  level.  A  shaft  should  be  built  and 
allowed  to  settle  before  connecting  up  to  the 
main  flue  to  avoid  fracture  in  the  brickwork. 
For  the  same  reason  it  is  advisable  shafts 


72 


should  stand  alone  without  connection  with 
any  surrounding  buildings.  The  circular 
form  of  chimney  is  best  and  most  economical, 
as  the  same  amount  of  material  covers  a 
greater  area,  and  the  effect  of  wind  pressure 
on  the  structure  is  less.  Taking  the  effect  of 
wind  pressure  upon  a  square  shaft  as  1,  the 
effect  upon  a  hexagonal  shaft  may  be  taken 
at  '75,  on  an  octagonal  shaft  '7,  and  upon  a 
circular  shaft  '5.  In  practice  it  is  customary 
to  provide  shafts  of  sufficient  weight  and 
stability  to  withstand  a  wind-pressure  of 
56  Ibs.  per  square  foot  of  surface  exposed,  an 
allowance  which  was  recommended  by  the 
Board  of  Trade  Committee  on  Wind  Pressure, 
and  which  is  well  in  excess  of  anything  likely 
to  be  realised.  In  calculations  for  stability  of 
shafts  no  value  is  attached  to  the  tensile  or 
adhesive  strength  of  the  mortar,  the  weight  of 
the  shaft  alone  must  be  adequate  to  resist 
overturning,  so  that  even  during  the  most 
severe  gale  of  wind  there  should  be  no  tension 
set  up  in  any  part  of  any  bed-joint.  If  a 
chimney  is  designed  with  the  thicknesses  of 
brickwork  prescribed  in  the  first  part  of  this 
article  its  stability  will  be  ensured. 

Chloride  of  Lime,  or  bleaching  powder, 
CaCl20,  dissolves  in  water  (except  the  im- 
purities) forming  chloride  and  hypochlorite 
of  calcium,  the  latter  only  being  available  as  a 
disinfectant  or  oxidiser.  The  powder  should  be 
dry  and  should  contain  about  |rd  of  its  weight 
of  "  available  chlorine"  (that  belonging  to  the 
hypochlorite).  It  keeps  for  some  time  when 
protected  from  light  and  air,  which  cause  it 
to  deliquesce  and  spoil,  while  C02  liberates 
hypochlorous  acid,  giving  rise  to  the  odour. 
It  is  a  bactericide  and  an  oxidiser  acting 
approximately  thus  :  (1)  when  alone  (a 
slow  action),  CaCl20  =  CaCl2  +  0:  (2)  with 
hydrochloric  and  some  other  strong  acids, 
immediately,  CaCl20  +  2HC1  =  CaCl2  +  H20 
+  C12  (free  chlorine) :  with  weak  sulphuric 
and  other  acids,  2CaCl20  +  H2S04  =  CaCl2  + 
CaS04  +  2HC10  (Hypochlorous  acid).  When 
mixed  with  whitewash  the  surface  remains 
damp,  owing  to  the  calcium  chloride.  For 


CHL 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


CHL 


sprinkling  use  1  part  to  10  or  12  of  water ;  for 
washing  the  person  1  to  100.  For  disinfecting 
rooms  several  applications  of  the  1  °/0  solution 
are  needed.1  If  strong  it  corrodes  metal  fittings, 
and  it  has  sometimes  perforated  the  siphons 
of  water  closets,  but  after  the  Maidstone 
typhoid  epidemic  in  1897  the  water  pipes  were 
sterilised  with  a  1  %  solution  of  chloride  of 
lime  acting  for  48  hours,  and  no  corrosion  was 
observed.  Traube  in  1894  stated  that  a 
quantity  of  chloride  of  lime  containing  one 
milligramme  of  available  chlorine  destroyed  in 
2  hours  all  the  bacteria  in  a  litre  of  water  (a 
proportion  of  1  per  million),  but  it  has  since 
been  proved  that  the  amount  required  is  much 
greater,  and  such  as  to  make  the  water  hard  and 
undrinkable.  Hypochlorite  of  soda,  in  the  form 
of  "  Chloros,"  or  electrolytic,  can  be  used  in- 
stead, and  the  writer  has  found  that  l/25,000th 
to  l/30,000thpart  of  available  chlorine  in  either 
of  the  three  forms  killed  B.  typhosus  in  10 
minutes.  The  strength  of  commercial  hypo- 
chlorites  in  available  Cl  (normal  33  %}  must 
always  be  known,  and  they  must  be  used  in  pro- 
portion to  this  figure.  Comparative  tests  with 
bleaching  powder  and  electrolytic  chlorine  for 
the  sterilisation  of  water  and  sewage  effluents 
show  that  the  latter  is  cheaper  and  more 
efficient,  and  it  is  probable  that  electrolytic 
plants  will  be  installed  in  those  cases  in  which 
a  permanent  treatment  is  required.  It  is  even 
possible  to  disinfect  crude  sewage,  as,  for 
example,  that  from  a  hospital,  prior  to  bacterial 
treatment,  but  in  this  case  the  cost  is  pro- 
portionally higher.  Schumacher,  and  Dunbar 
and  Korn,  conducted  some  elaborate  trials  at 
Hamburg  in  1904  with  bleaching  powder,  and 
established  the  quantities  necessary  fo'r  the 
sterilisation  of  sewage,  whilst  Chloros  has  since 
been  used  by  the  London  Water  Board  for 
Hertford  Sewage,  and  Rideal  has  similarly  used 
"  oxychlorides  "  (sodium  hypochlorite  prepared 
electrically)  on  the  Guildford  sewage  with 
satisfactory  results.  (See  "  ELECTROLYSIS.") 

1  The  Board  of  Agriculture  and  Fisheries  prescribes 
"al%  (minimum)  solution  of  chloride  of  lime  con- 
taining not  less  than  30%  of  available  chlorine." 
Diseases  of  Animals  (Disinfection)  Order  of  1906. 


In  the  United  States  the  Department  of 
Agriculture  in  Bulletin,  115,  has  further  in- 
vestigated the  subject,  comparing  the  effect  of 
copper  sulphate  and  chlorine  for  the  disin- 
fection of  sewage  effluents  for  the  protection 
of  public  water  supplies.  At  Ilford  bleaching 
powder  has  been  used  for  sterilising  the  effluent 
from  the  sewage  works  after  chemical  precipita- 
tion. About  5  parts  per  million  of  available 
chlorine  and  a  storage  of  about  2  hours  re- 
moves nearly  all  the  bacteria,  including  B.  coli 
and  any  typhoid  bacilli  present,  from  an 
ordinary  sewage  effluent  after  bacterial 
treatment  in  a  modern  percolating  filter. 

S.  R. 

Chlorine   in   Water   and    Sewage.— 

Chlorides  in  water  (and  sewage)  are  usually 
recorded  as  chlorine.  High  chlorides,  unless 
derived  from  rocks  or  from  the  sea  (which 
contains  about  1'9/^of  Cl),  point  to  contamina- 
tion by  urine,  which  contains  up  to  1  %  of 
NaCl,  as  distinguished  from  that  by  faeces, 
which  contain  much  less,  hence  the  chlorine 
figure  is  sometimes  a  valuable  index  of  the 
pollution.  The  urine  averages  about  1J  litres 
per  head  per  day,  with  a  mean  chlorine  of 
about  0'45  %  or  450  parts  per  100,000,  whereas 
in  most  ordinary  waters  the  chlorine  is  only 
1  to  2  parts ;  in  weak  domestic  sewages  it  is 
about  7,  in  stronger  ones  it  may  be  40  or  50, 
and  a  common  average  is  10.  For  comparing 
sewages  it  is  often  useful  to  calculate  the 
analyses  to  a  uniform  Cl  figure,  say  10  parts, 
and  the  ratio  of  the  Cl  to  the  amounts  of  the 
different  forms  of  nitrogen  shows  the  progress 
of  the  purification.  We  may  note  that 
(1)  rain,  unless  it  has  passed  over  a  polluted 
surface,  always  diminishes  the  Cl ;  (2)  a 
decrease  in  the  Cl  of  a  well  may  indicate 
surface  infiltration ;  (3)  a  good  well  yields  a 
fairly  constant  figure.  The  Massachusetts 
reports  give  maps  of  "  Isochlors,"  or  lines  on 
which  the  subsoil  water  shows  equal  Cl,  but 
in  many  countries  agriculture  renders  these 
illusory.  In  rivers  and  estuaries,  and  on 
coasts,  Cl  determinations  enable  us  to  trace 
the  course  of  sewage  and  of  fresh  or  s-alt  water 


73 


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ENCYCLOPEDIA  OF 


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(as  recently  at  Dublin,  South  end,  and  other 
places),  and  also  the  infiltration  of  the  sea 
into  water  pipes  and  wells,  as  at  Eastbourne, 
and  the  passage  of  trade  effluents.  (See 
"  ANALYSIS,  CHEMICAL  "  ;  "  EFFLUENTS  AND 
STANDARDS  OF  PURITY";  "WATER,  CHEMICAL 
ANALYSIS  OF.") 

Cholera. — Cholera  is  a  specific  infectious 
disease    characterised    by    violent    diarrhoea 
and    collapse,    causing    a    heavy    mortality, 
often  reaching  50  %,  amongst  those  attacked. 
In  certain  parts  of   India   it  appears   to  be 
continuously     prevalent,     "  endemic,"      and 
from  time  to  time  it  follows   the  routes  of 
travel  to  the  most  distant  parts  of  the  world. 
Sometimes  it  travels  slowly  along  the  route 
of  caravan  traffic,  at  others  it  travels  more 
rapidly   along   the   course  of   rivers,  and    at 
others  it  is  carried    rapidly   by    ships   from 
port  to  port.     Several  times  during  last  cen- 
tury it  entered  British  ports,  and  in  1832, 
1849,  1854,  and  1866,  wide-spread  epidemics 
occurred;  but  in  1866  the  invasion  was  far 
less  serious  than  on  previous  occasions,  and 
since   that   date   although  the  infection  has 
been   several   times  imported  the  secondary 
cases  have  been  few  in  number  and  practically 
confined  to  the  port  of  entry.     The  disease  is 
due  to  a  specific  poison,  a  toxin,  produced  by 
a  spirillum,  the  cholera  bacillus,  during  its 
growth  in  the  large  intestine.     The  organism 
does  not  produce  spores,  and  it  can  readily  be 
grown  in  nutrient  broth  and  on  various  solid 
media.     It  apparently  lives  only  a  short  time 
in  water,  but  may  survive  a  long  time  in  soil 
under  favourable  conditions.     The  evidence, 
however,  on  these  points  is  very  conflicting. 
Like  the  infection  of  typhoid  fever,  it  is  chiefly 
disseminated  by  water,  milk,  and  articles  of 
food  and  drink  ;  but  it  can  also  spread  from 
person  to  person,  and  it  is  especially  prone 
to  prevail  where  the  sanitary  conditions  are 
unsatisfactory.     The  spirilla  are  rarely  if  ever 
found  in  the  blood  or  the  urine  of  the  patient, 
but    the   rice   water  stools  contain   them  in 
myriads.     From  surfaces  which  have  become 
contaminated  flies  may  convey  the  infective 


material  to  water,  milk,   &c.,  and   so  cause 
spread  of   the  disease ;  but   doubtless   water 
supplies  are  most  prone  to  pollution  from  the 
wrashings   of    soil    which    has    been    fsecally 
contaminated.     The  last  epidemic  in  Europe, 
which  occurred   in   Hamburg   in   1892,   was 
due    to    the    use    of    unfiltered    water    from 
the    river    Elbe.      Altona,    lower    down   the 
river,  using  still  more  grossly  polluted  water 
from  the  same  river  after  careful  filtration, 
practically   escaped   until   by   an   accident  a 
little  imperfectly  filtered  water  was  allowed  to 
enter  the  mains  when  a  small  outbreak  quickly 
occurred.     The  Hamburg   epidemic   resulted 
in  the  loss  of  over  8,000  lives  within  a  period 
of     about     three     months.      The    mortality 
amongst    those    attacked    was    over     40   %. 
Within  two  to  five  days  from  the  ingestion 
of  the  specific  poison,  the  first  symptoms  of 
the  disease  appear,  and  frequently  the  early 
cases  of  an  epidemic  are  so  mild  in  character 
as  to  be  regarded  as  ordinary  diarrhoea.     The 
later  occurrence  of  typical  and  rapidly  fatal 
cases  clears   up  the  diagnosis.     In  districts 
liable  to  invasion  any  outbreak  of  diarrhoeal 
disease,   however   mild,  should   be   carefully 
watched,    or   the   train  may  be   laid  for  an 
extensive  outburst  before  the  real  danger  is 
realised.      Wherever     pure    water     supplies 
have  been  introduced  the  ravages  of  cholera 
have  been  held  in  check.     Thus  in  Lahore 
the  average  death-rate  from  cholera  fell  from 
1-07  per  1,000  population  to  0'07  after  the 
provision  of  a  public  water  supply,  whereas 
the  death-rate  increased  in  the  district  around, 
where  the  water  supplies  remained  as  before. 
The  annual  pilgrimage  of  Mohammedans  to 
Mecca  almost    invariably  brings  cholera   in 
its  train,  though  the  great  attention  now  paid 
to  the  wells  en  route  has  considerably  reduced 
the   risk   of   a   serious   epidemic.      Cases   of 
cholera  can  only  enter  this  country  through 
the  ports,  and  the  Local  Government  Board 
has  issued  regulations  for  the  prevention  of 
such     importation.1      Any     vessels     coming 
within  three  miles  of   the  coast  of  England 
1  P.  H.  A.,  1875,   s.  130;  P.   H.  (Port)  A.,  1896; 
P.  H.  A.,  1896. 
74 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


CIS 


and  Wales,  and  having  a  case  of  cholera  (or 
yellow  fever  or  plague)  on  board  must  hoist 
at  the  mast-head  a  large  yellow  and  black 
flag.  All  vessels  from  foreign  ports  are 
boarded  by  Customs  officers,  and  if,  upon 
inquiry,  they  have  reason  to  suspect  that  a 
ship  is  infected,  it  is  ordered  to  be  moored  in 
a  place  set  apart  for  the  purpose  until  the 
medical  officer  of  the  port  has  boarded  and 
examined  the  passengers  and  crew.  A  vessel 
is  deemed  to  be  infected  in  which  there  is  any 
case  of  cholera  (or  yellow  fever  or  plague),  or 
in  which  there  has  been  a  case  whilst  it  was 
in,  or  since  it  has  left  the  port  of  departure. 
The  medical  officer  of  health  can  detain  the 
vessel  for  a  period  not  exceeding  two  days. 
Infected  persons  must  be  sent  to  a  hospital, 
suspected  persons  may  be  detained  two  days 
to  enable  a  diagnosis  to  be  made,  whilst  those 
who  are  well  must  be  permitted  to  land,  pro- 
vided they  give  their  names  and  addresses, 
and  intended  destinations.  These  names  and 
addresses  are  sent  to  the  sanitary  authorities 
for  the  districts  into  which  the  persons  are 
going  and  the  medical  officers  of  health  for 
the  respective  districts  then  exercise  such 
supervision  as  may  be  deemed  desirable  until 
the  danger  period  is  past.  In  some  countries 
vessels  are  detained  in  quarantine  for  a  con- 
siderable period,  but  the  experience  gained  at 
British  ports  has  shown  that  such  prolonged 
quarantine  is  totally  unnecessary  whilst  it 
seriously  dislocates  trade,  and  causes  heavy 
pecuniary  loss  to  shipowners  and  passengers. 
During  the  day  or  two's  detention  the  vessel 
can  be  disinfected,  and  bedding,  clothing,  &c., 
be  submitted  to  steam  for  sterilisation,  the  bilge 
water  pumped  out,  and  all  water  receptacles 
disinfected.  The  master  of  the  vessel  must 
carry  out  or  permit  to  be  carried  out  neces- 
sary disinfecting  and  cleansing  operations 
and  must  burn  or  otherwise  destroy  all 
infected  articles  if  ordered  to  do  so  by  the 
sanitary  authority  or  medical  officer  of  health. 

J.  C.  T. 

Cisterns  (Vessels  for  the  Storage  of 
Water  in  Buildings). — Although  drinking 


water  is  best  drawn  direct  from  the  mains, 
where  mains  and  a  constant  supply  are  avail- 
able, water  must  be  stored  in  all  cases  for 
eventualities,  such  as  during  periods  of  frozen 
mains  or  repairs.  Cisterns  are  constructed  of 
a  variety  of  materials  which  should  be  selected 
with  due  regard  to  the  characteristics  of  the 
water  to  be  stored.  Soft  water  absorbs  lead 
and  this  material  must  therefore  be  avoided 
if  the  water  has  any  tendency  to  act  upon  it. 
Zinc  lined  and 
galvanised  iron 
cisterns  are  also 
undesirable  in 
connection 
therewith,  al- 
though less 
objectionable 
than  lead. 
Copper  -  lined 
cisterns,  unless 
tinned,  are  even 
more  objection- 
able, as  copper 
is  a  metal  which 
is  attacked  very 
energetically  by 
water  and  air, 
and  the  salts  of 
copper  are  very 
dangerous.  Tin, 
however,  has  a 
great  affinity  for 
copper.and  forms 
a  very  durable 
and  protective 
coating  when  thoroughly  applied.  Tinned 
copper  is  therefore  probably  the  best  metallic 
lining  which  can  be  used  for  cisterns  intended 
for  the  storage  of  water  having  a  tendency  to 
act  upon  metals. 

Other  suitable  cisterns  which  are  safe  and 
desirable  with  all  kinds  of  water  are,  enamelled 
iron  cisterns  made  in  sizes  to  hold  from  40 
to  500  gallons  of  water ;  porcelain  enamelled 
stoneware  cisterns  made  of  capacities  up 
to  about  60  gallons,  and  fireclay  salt  glazed 
cisterns  which  are  obtainable  in  sizes 


Cisterns. 


75 


€IS 


ENCYCLOPAEDIA  OF 


CLE 


sufficiently   large   to   hold   from   400  to  500     absolutely  air-tight,  both  in  itself  and  in  its 


gallons  of  water.  With  all  these  it  is  neces- 
sary to  exercise  care  in  selection,  as  the 
enamelling  or  glazing  is  frequently  rough  or 
fractured.  Stoneware  or  fireclay  cisterns  are 
for  this  reason  occasionally  apt  to  prove 
slightly  porous.  Slate  cisterns  are  also  good, 
and  come  next  to  stoneware  cisterns  in  clean- 
liness and  suitability  for  the  storage  of  water. 
They  are,  however,  heavy,  costly  and  liable  to 
leak.  Their  joints  should  be  made  with 
materials  other  than  red  or  white  lead,  as  the 
oxides  of  lead  are  soluble  in  most  waters  and, 
of  course,  poisonous.  Black  wrought-iron 
cisterns,  painted  or  washed  with  lime  or 
cement,  are  occasionally  used.  The  cement 
or  lime-washing,  however,  soon  wears  off,  and 
needs  frequent  renewal ;  whilst  painting  is 
not  always  suitable  owing  to  the  lead  con- 
tained in  the  paint.  If  iron  cisterns  are  used 
the  safest  and  most  lasting  protective  coating 
would  be  a  quick-drying  asphalte  varnish,  of 
which  two  or  three  coats  should  be  applied. 

Cisterns,  and  especially  such  of  them  as 
are  connected  to  taps  for  supplying  drinking 
water,  are  amongst  the  most  important  of 
the  sanitary  fittings  of  a  house,  and  require 
at  least  as  much  consideration  as  water  closets, 
or  other  sanitary  appliances.  They  should 
be  placed  in  apartments  kept  exclusively  for 
the  purpose  and  chosen  with  the  utmost  care. 
The  room  or  rooms  in  which  they  are  placed 
should  be  well  lighted,  warm  in  winter  and 
cool  in  summer,  and  as  far  removed  as  pos- 
sible from  those  portions  of  the  house  in 
which  sanitary  fittings  or  bedrooms  are 
situated.  All  care  must  be  taken  to  prevent 
the  pollution  of  the  water  by  dust,  vermin  or 
foul  air,  for  which  purpose  each  cistern  should 
be  provided  with  a  close  fitting  removable 
cover.  When  vermin  and  dirt  are  the  only 
impurities  to'  be  guarded  against,  a  wooden 
lid,  constructed  of  tongued  and  grooved  boards 
or  of  matchboarding,  will  be  sufficient ;  but  if 
there  be  the  slightest  possibility  of  contamina- 
tion by  foul  air  or  gases — such  as  from  bed- 
rooms or  from  ventilation  pipes  on  drains  or 
from  the  house — then  the  lid  should  be 


fixing  to  the  cistern.  The  ideal  cistern,  as  was 
pointed  out  by  the  Commission  on  the  East 
London  water-supply,  would  be  a  mere  local 
enlargement  of  the  service  pipe,  perfectly  closed 
except  for  a  minute  valve,  and  preferably  of  a 
conical  shape,  so  as  to  be  self -cleansing.  Such 
cisterns  are  upon  the  market  (sec  Figure,  p.  75). 

In  order  to  efficiently  guard  drinking  water 
against  aerial  contamination,  it  is  also  essen- 
tial that  all  ordinary  cisterns  containing  such 
water  should  have  their  overflow  pipes 
arranged  to  discharge  into  the  open  air  at  some 
point  at  which  the  overflow  pipe  is  not  exposed 
to  emanation  from  drains,  sanitary  fittings,  or 
other  sources  of  polluted  air.  Nor  must  any 
water  closets,  urinals,  or  housemaids'  slop- 
sinks  be  flushed  directly  from  the  service  pipes 
or  from  any  cistern  containing  potable  water. 
The  latter  would  be  liable  to  be  polluted  by 
means  of  foul  air  conveyed  to  them  from  the 
sanitary  fittings  through  the  flushing  pipes ; 
whilst,  in  the  case  of  service  pipes,  there  is  a 
strong  tendency  for  foul  air  to  be  drawn  into 
these  when  emptied  through  any  cause. 

It  is  for  these  reasons  that  most  sanitary 
authorities  require  the  fittings  mentioned  to 
be  flushed  from  separate  cisterns.  The 
requirements  of  water  companies  and  corpo- 
rations, by  which  it  is  necessary  to  provide 
water  -  waste  preventing  cisterns,  are  also 
beneficial,  although,  perhaps,  framed  mainly 
for  the  prevention  of  waste.  For  details  of 
these  see  "WASTE  PREVENTERS."  G.  J.  G.  J. 

Cleaning  Eye. — A  round  aperture  on  a 
pipe,  usually  in  the  nature  of  a  branch  socket, 


CLI 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


COL 


FIG.  3. 


provided  for  cleaning  purposes  and  fitted  with 

a  movable  cap 
or  cover  capable 
of  being  closed 
air -tightly. 
Cleaning  eyes 
are  usually  pro- 
vided on  waste 
pipes ;  also  on 
disconnecting 
traps  for  giving 
access  to  that 
portion  of  the 
drain  which  lies  between  the  trap  and  the 
sewer.  (See  also  "  ACCESS  PIPES.") 

Clinker  from  Destructors. — (See  "DE- 
STRUCTORS.") 

Coagulents. — (See  "  FILTRATION.") 

Coarse  Beds,  Bacterial. — (See  "  SEWAGE 
DISPOSAL.") 

Cocks. — A  valve  or  tap  for  controlling  the 
flow  of  water  through  or  from  a  pipe.  Strictly, 
a  cock  is  a  fitting  having  a  conical  plug  with 
its  axis  at  right  angles  to  the  flow  through  the 
pipe  and  provided  with  a  slot  or  opening  which, 
when  in  the  direction  of  the  flow,  permits 
water  to  pass  through.  When  the  slot  is  at 
right  angles  to  the  flow  the  water  is  turned 
.off.  Cocks  are  not  desirable  fittings  as  they 
shut  off  the  water  too  suddenly  and  give  rise 
to  the  percussion  known  as  water  hammer 
when  the  water  is  under  pressure.  (See  also 
"  VALVES.") 

Colloidal    Matters    in    Sewage. — The 

substances  in  sewage  which  are  not  removed 
by  ordinary  filtration  or  sedimentation  are  of 
two  kinds,  (1)  colloidal,  amorphous,  of  con- 
siderable viscosity,  and  almost  incapable  of 
diffusion,  like  albumen  or  gum ;  and  (2)  crystal- 
loid, capable  of  crystallisation  and  diffusion, 
and  much  less  viscous,  like,  typically,  common 
salt.  The  former  are  in  a  more  or  less 
unstable  condition,  and  Graham,  whose  work 
first  made  the  difference  distinct,  introduced 
the  terms  still  in  use  of  "  sol "  for  their 
apparent  solution,  and  "gel"  for  the 


gelatinous  result  of  their  coagulation  or 
change ;  the  words  are  frequently  extended  into 
"hydrosol'"  and  "  hydrogel "  to  include  in 
them  the  presence  of  water.  Although  most 
of  the  colloids  are  organic,  probably  all  solids 
in  conjunction  with  liquids  are  capable  of 
assuming,  at  least  temporarily,  the  colloidal 
state  :  that  is  (1)  they  may  be  in  such  a  fine 
state  of  division  as  not  to  be  separable  by 
filtration ;  (2)  they  leave  the  liquid  clear 
or  only  slightly  turbid,  so  that  their 
presence  may  be  solely  detectible  by  the 
ultra-microscope — that  is,  by  a  concentrated 
beam  of  reflected  light;  and  (3)  they  can 
be  flocculated  and  precipitated  by  addition 
of  small  quantities  of  chemical  substances, 
also  sometimes  by  heat,  and  sometimes  by 
adhesion  to  surfaces.  In  forming  a  "gel" 
a  colloid  always  combines  with  and  entangles 
a  considerable  amount  of  other  substances 
present  ;  this  property,  especially  when  it 
affects  matters  in  solution  is  called  "adsorp- 
tion," and  is  a  conspicuous  feature  of  methods 
of  precipitation  of  sewage  by  the  inorganic 
"  gels  "  of  ferric  oxide  and  alumina,  obtained 
by  adding  an  acid  salt  like  "  alumino-ferric," 
and  then  lime.  In  this  case,  since  a  number 
of  organic  substances  prevent  the  precipitation 
of  metallic  oxides,  it  is  necessary  to  ascertain 
the  quantities  by  trial,  in  order  that  the 
effluent  should  not  contain  more  than  traces 
of  the  precipitant.  It  is  possible  by  suitable 
chemicals  to  greatly  decrease  the  colloids  in 
sewage,  but  with  considerable  expense  and  an 
excessive  sludge.  A  large  portion  of  these 
colloids  are  deposited  in  simple  sedimentation, 
if  time  can  be  allowed,  but  this  deposition  is 
greatly  accelerated  by  their  property  of 
adhesion  to  surfaces.  In  filtration  a  slimy 
layer  forms  on  the  material,  and  acts 
mechanically,  by  entangling  suspended  matter, 
and  biologically  by  the  large  number  of 
organisms  growing  in  it  ("Zooglcea"),  which 
occasion  chemical  changes  in  the  liquid  passing 
through,  and  if  properly  managed  effect  a  great 
purification.  At  the  same  time  the  working 
of  filters  is  largely  influenced  by  the  viscous 
properties  of  the  colloids,  acting  by  (1)  causing 


77 


COL 


ENCYCLOPAEDIA   OF 


COM 


the  liquid  itself  to  flow  more  slowly ;  (2) 
diminishing  the  capacity  on  account  of  the 
gelatinous  deposit  on  the  medium ;  (d)retarding 
the  previous  deposition  of  suspended  matter. 
Hence  the  advantage  of  a  preliminary  passage 
over  surfaces,  as  in  the  Scott-Moncrieff  culti- 
vation tank  or  in  Travis's  "  hydrolytic  " 
arrangement.  Besides  the  mucous  matters  in 
domestic  sewage,  a  number  of  other  viscous 
substances  are  often  added  by  manufactures 
and  may  necessitate  some  form  of  chemical 
precipitation.  Blitz's  work  on  the  different 
polarity  of  the  colloids,  the  gummy  and  the 
albuminoid  class  being  electrically  negative, 
and  the  metallic  hydroxides  positive,  helps  to 
explain  why  definite  quantities  of  precipitants 
are  necessary,  and  why  electric  currents, 
passage  over  surfaces,  or  addition  of  electrolytes 
can  cause  coagulation.  Anaerobic  action  in 
septic  tanks,  and  defective  aeration  in  filters 
increase  the  amount  of  colloid  matter  in  the 
state  of  "  hydrosol,"  which  also  usually 
becomes  higher  with  increased  temperature, 
while  high  nitrification  generally  coincides 
with  low  colloids  in  the  final  effluent.  The 
amount  of  these  substances  in  sewage  has 
been  determined  by  dialysing  the  filtered 
liquid  through  parchment,  or  through  porous 
porcelain  (Thorp)  :  upwards  of  30  to  50  %  of 
the  organic  matter  will  not  diffuse  and  is  there- 
fore colloid.  A  similar  figure  is  obtained  more 
rapidly  by  precipitating  by  basic  ferric  acetate. 
Fowler  for  his  "Clarification  Test "  adds  to 
200  c.c.  of  the  sample  2  c.c.  of  a  5  %  solution 
of  sodium  acetate  and  2  c.c.  of  a  10  %  ferric 
ammonium  alum solution, boils  for twominutes, 
cools,  filters,  and  analyses  the  clear  liquid. 

O'Shaughnessy  found  (Birmingham  sewage) 
that  the  matter  which  separates  on  allowing  a 
clear  septic  tank  to  stand  has  only  a  faint 
odour,  is  extremely  stable,  and  even  when 
incubated  with  water  under  the  most  favourable 
circumstances  decomposes  with  extreme  slow- 
ness. These  properties  sharply  distinguish  this 
matter  from  the  original  sewage  sludge.  He 
mentions  incidentally  that  the  colloid  matter 
usually  present  in  land  effluents  is  very  small 
in  quantity  and  contains  much  mineral  matter 


consisting  mainly  of  ferric  h}"drate  and  silica. 
Other  investigators  l  have  shown  that  the  pro- 
ducts of  a  proper  septic  fermentation  and  sedi- 
mentation of  sewage  resemble  the  humus  of 
peat,  are  practically  inoffensive,  and  contain 
about  7  parts  of  carbon  to  1  of  nitrogen, 
associated  with  iron  and  other  inorganic 
matter.  S.  R. 


Columbaria.  —  (See     "  CREMATORIA 
COLUMBARIA.") 


AND 


Combined  Drainage  System. — The  com- 
bined drainage  system  is  that  in  which  the 
surface-water  from  a  district  is  carried  away 
by  the  same  sewers  which  convey  the  sewage. 
Most  English  cities  and  towns  are  drained  on 
this  system,  the  original  practice  having  been 
to  turn  sewage,  rain-water,  and  even  subsoil- 
water  into  the  same  set  of  sewers.  The  points 
urged  in  favour  of  the  combined  system  are 
that  it  is  simpler  and  cheaper  to  have  one  set 
of  sewers  than  two,  and  that  the  rain-water 
admitted  to  the  sewers  is  valuable  for  flushing 
them.  Its  disadvantages  are  the  excessively 
large  sewers  which  it  generally  necessitates, 
and  the  consequent  sluggishness  of  the  dry- 
weather  flow  in  them ;  and  the  difficulty  of 
dealing  with  large  volumes  of  storm  water  at  the 
outfall.  Whether  the  sewage  is  to  be  purified 
on  land  or  in  artificial  works,  it  is  important 
to  keep  the  flow  within  moderate  limits ;  and 
where  it  has  to  be  pumped,  the  admission  of 
surface-water  will  generally  entail  a  very  large 
addition  to  the  cost  of  this  operation.  The 
"combined  system  "  is  therefore  very  generally 
discarded  in  favour  of  the  "  separate  system  " 
(which  see),  though  for  various  practical  reasons 
it  is  seldom  possible  to  carry  out  the  latter  in 
its  entirety.  The  washings  from  the  roads, 
especially  after  a  long  spell  of  dry  weather, 
are  often  fouler  than  the  sewage.  London  is 
a  good  example  of  a  city  sewered  on  the 
combined  system.  A.  J.  M. 

Commin  Separator,  (Sewage  Dis- 
posal).— This  consists  essentially  of  a  shallow 

1  Adeney,  "Trans.  Roy.  Dublin  Sec.,"  Sept.,  1895, 
and  Aug.,  1897  ;  Rideal,  "  Brit.  Assoc.  Reports,"  1901. 


78 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


COM 


tank  with  grit  chamber  of  sufficient  capacity 
to  steady  the  flow  of  sewage  so  as  to  permit  of 
the  heavier  suspended  solids  sinking  and  the 
lighter  matters  rising.  The  object  of  the 
"  separator  "  being  to  thus  remove  the  coarser 
suspended  solids  in  the  sewage  in  order  to 
render  the  liquid  portion  capable  of  further 
treatment  upon  bacteria  beds  or  by  other 
means.  With  the  object  of  assisting  in  the 
settlement  of  the  solids,  the  flow  from  the 
tank  is  divided  over  the  edges  of  a  large 
number  of  small  channels  at  the  surface  all  set 
level  with  each  other,  thus  forming  a  long 
length  of  weir,  and  the  velocity  of  approach  of 
the  sewage  sought  to  be  secured  is  such  as  to 
ensure  the  precipitation  of  the  finely  divided 
solids.  Like  ordinary  settling  tanks,  these 
"  separators  "  should  be  provided  in  duplicate 
for  continuous  work  so  that  a  section  may  be 
cleared  daily.  A  "  separator  "  33  ft.  x  18  ft.  : 
is  considered  capable  of  treating  30,000  gallons 
per  hour.  A  separator  plant  is  in  use  at 
Dorchester  where  the  tank  is  divided  into 
four  compartments,  the  sludge  from  one  of 
which  is  emptied  daily  by  first  removing  the 
whole  of  the  supernatant  water.  The  popu- 
lation of  Dorchester  is  about  10,000  and  the 
dry  weather  flow,  which  is  diluted  by  leakage 
into  the  sewers,  45  gallons  per  head.  The  grit 
chambers  in  connection  with  the  separators 
are  reported  to  remove  some  4  or  5  tons 
of  stiff  sludge  per  day  and  the  separator 
another  f  of  a  ton.  After  leaving  the 
"  separator  "  the  sewage  passes  into  what  was 
formerly  a  septic  tank,  now  used  as  a  sedi- 
mentation tank,  in  this  way  a  further  2  to 
3  tons  of  sludge  is  removed  daily,  due  appar- 
ently to  the  much  larger  capacity  of  the  septic 
tank.  Since  the  Dorchester  plant  was  con- 
structed improvements  have  been  introduced 
with  the  object  of  overcoming  the  difficulties 
in  working  experienced  in  that  installation. 
(See  also  "  KESSEL-SEPARATOR.") 

Compensation  Water.— When  the  water- 
shed of  the  upper  reaches  of  a  stream  is 
appropriated  by  a  public  water  authority,  a 
definite  statutory  obligation  is  usually  imposed 


79 


upon  such  authority  to  deliver  into  the  water- 
course flowing  from  the  watershed  proposed 
to  be  utilised  for  purposes  of  a  public  supply, 
a  stipulated  quantity  of  water  daily  for  the  use 
of  mill  owners,  agriculturists,  and  others 
interested  in  the  water-rights  of  the  stream. 
The  water  so  supplied  is  known  as  "  com- 
pensation water."  (See  "  WATER  SUPPLY.") 

Compressed  Air. — Compressed  air  is  ex- 
tensively used  for  transmitting  power  to 
distances,  raising  water  from  boreholes,  lifting 
sewage  by  displacement,  &c.,  &c.  According 
to  the  well-known  law  of  gases,  the  pressure 
of  a  quantity  of  dry  air  is  inversely  pro- 
portional to  its  volume,  provided  its  tempera- 
ture remains  the  same;  thus  if  a  cylinder 
full  of  "  free  "  air,  i.e.,  air  at  atmospheric 
pressure  (14*7  Ibs.  per  square  inch),  were 
compressed  by  a  piston,  without  increase  of 
temperature  (isotherrnally),  to  half  its  former 
volume,  the  resulting  pressure  would  be 
29'4  Ibs.  per  square  inch.  When  air  is 
compressed,  however,  its  temperature  is  raised, 
and,  unless  the  heat  due  to  the  work  of 
compression  could  be  abstracted  during  the 
process,  such  compression  would  not  be 
performed  "  isothermally "  and  the  above 
conditions  would  fail  to  be  realised.  If  the 
temperature  acquired  by  compression  is 
retained,  the  rise  of  pressure  will  be  more 
rapid  than  the  inverse  ratio  of  the  volume,  and 
will  assume  the  proportion  known  as 
"  adiabatic "  (no  heat  passing).  As  this 
heat  will  be  dissipated  after  the  air  leaves 
the  compressing  cylinder,  a  proportionate 
shrinkage  in  volume  and  loss  of  pressure  will 
take  place,  with  the  result  that  a  corresponding 
amount  of  work  will  have  been  wasted. 
Erom  this  it  is  evident  that  the  more  closely 
compression  follows  isothermic  conditions, 
the  more  efficient  will  be  the  process.  To 
remove  the  heat,  compressor  cylinders  and, 
in  some  cases,  the  pistons,  are  water  jacketted ; 
but  as  air  is  a  slow  conductor  of  heat  this  is 
only  a  partial  remedy.  A  further  attempt 
towards  economy  consisted  in  spraying  water 
into  the  cylinder,  but  the  latter  and  similar 


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plans  were  open  to  practical  objections.  The 
best  solution  of  the  difficulty  was  to  divide 
the  compression  into  two  or  more  stages  and  to 
cool  the  air  between  each  stage  in  a  kind  of 
surface  condenser.  As  the  difficulties  of 
cooling  during  compression  increase  with  the 
pressure,  it  is  usually  advisable  to  employ 
"  stage  "  compression  for  pressures  over  about 
70  Ibs.  per  square  inch.  The  air,  after  being 
compressed,  may  be  stored  in  receivers  if 
the  work  is  of  a  nature  to  require  it,  and 
may  be  conducted  considerable  distances 
with  slight  loss.  In  employing  compressed 
air  as  a  motive  power  behind  a  piston  (as 
steam  in  an  engine)  the  air  is,  when  practic- 
able, allowed  to  expand  until  at  the  end 
of  the  piston  stroke  it  is  nearly  down  to 
atmospheric  pressure.  As  air  is  heated  by 
compression  it  will,  conversely,  be  cooled  by 
expansion ;  this  leads  to  a  further  loss  in 
the  motor,  and  may  also  cause  trouble  at 
the  exhaust  ports  by  freezing  the  moisture 
contained  in  the  air.  The  air  is,  therefore, 
re-heated  before  it  enters  the  motor,  usually 
by  passing  it  through  a  jacket  or  coil  heated 
by  some  inexpensive  fuel.  The  gain  in 
efficiency  far  outweighs  the  cost  of  re-heating. 
(See  "  Am  COMPRESSOR.")  E.  L.  B. 

Concrete. — Formerly  lime  concrete  was 
largely  used  for  foundation  work  on  land,  but 
it  is  now  unknown,  if  we  except  the  occasional 
use  of  lias  lime  for  the  purpose.  This  is 
due  to  the  abundance  and  low  price  of 
Portland  cement  which  sets  well  under  all 
conditions  and  produces  a  far  better  result. 
Concrete  is  generally  described  as  consisting 
of  a  matrix  and  aggregate,  the  matrix 
being  Portland  cement  and  sand  in  the  form 
of  mortar,  and  the  aggregate  the  large 
material  forming  the  bulk  of  the  mass,  such 
as  stone,  gravel,  brick,  &c.  The  proportion 
of  cement  used  is  the  main  element  of  cost 
and  it  is  therefore  kept  down  to  the  lowest 
limit  consistent  with  the  strength  required 
in  the  mass.  Where  the  mass  is  subject 
mainly  or  wholly  to  compression  a  weak 
mixture  only  is  necessary,  say  1  part  of 


cement  to  8  of  the  aggregate;  this  would 
apply  to  concrete  in  heavy  retaining  walls 
and  under  the  base  of  ordinary  walls.  For 
basement  floors  where  it  is  subject  to  irregular 
loading  and  unequal  expansion  of  the  soil 
below,  1  to  6  is  more  suitable,  but  for  modern 
reinforced  concrete  work  1  to  4  is  found 
necessary.  The  aggregate  may  be  varied 
according  to  what  is  available,  broken  stone, 
brick,  furnace  slag,  flints,  flint  gravel,  shore 
ballast,  purnice-stone,  or  coke  breeze.  The 
limitations,  however,  should  be  made  that  coke 
breeze  should  only  be  used  for  dry  situations 
such  as  upper  floors,  and  that  only  brick, 
furnace  slag,  pumice-stone,  or  coke  breeze 
should  be  used  for  fireproof  or  fire-resisting 
floors.  Ked  ballast  from  burnt  clay  is  of 
no  value  for  concrete.  The  material  used 
should  be  graded,  that  is,  of  various  sizes 
from  J  in.  up  to  1  in.  as  a  maximum  for 
fireproof  floors  and  reinforced  work  generally, 
and  up  to  2  in.  as  a  maximum  for  other  work. 
The  character  of  the  aggregate  determines  the 
proportion  of  sand,  which  should  be  sufficient 
to  fill  the  interstices,  and  the  cement  should 
then  be  sufficient  to  coat  every  particle  of 
sand  and  aggregate  and  fill  up  the  smaller 
interstices.  Generally  speaking,  this  will  give 
mixtures  of  1 :  2 :  4,  that  is,  1  cement,  2  sand, 
4  aggregate,  for  floors  and  reinforced  work,  and 
1 :  2^  or  3 :  6,  to  1 :  3  :  8,  for  other  purposes. 

MIXING. — For  hand-mixing  a  wooden  plat- 
form should  be  laid  down  to  avoid  any  earthy 
mixture,  say,  a  dozen  scaffold  boards  laid 
side  by  side  on  a  level  piece  of  ground.  An 
open  frame  or  box  with  no  top  or  bottom, 
3  ft.  square  and  18  in.  deep  (inside 
dimensions),  should  be  used  to  measure  the 
large  aggregate;  this  will  contain  ^  cu.  yd., 
equal  to  13£  cu.  ft.,  when  filled  level.  Then 
a  similar  frame,  2  ft.  by  2  ft.  by  \\  ft.  deep,  if 
placed  on  top  of  the  other  and  filled  with 
sand  would  give  the  right  proportion  for 
ordinary  foundations.  Then  2£  cu.  ft.  of 
cement  will  be  required,  or  If  bushels,  and 
this  is  usually  the  total  amount  contained  in 
a  two-bushel  sack  of  cement,  so  that  the  sack 


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of  cement  is  emptied  on  top  of  the  sand 
without  needing  any  box  to  measure  it.  The 
boxes  are  then  removed,  and  two  men 
standing  on  opposite  sides  shovel  the  material 
over  so  as  to  mix  it.  A  second  pair  of  men 
continue  the  process,  until  the  colour  is 
uniform  ;  then  they  turn  it  back  again  while 
it  is  being  watered  through  a  rose  so  as  to 
moisten  it  completely  throughout  the  mass 
without  washing  any  cement  away.  It  is 
then  filled  into  barrows  and  wheeled  away  at 
once  to  the  trench  ;  if  the  trench  is  shallow 
it  may  simply  be  tipped  in,  but  if  deep  the 
concrete  should  slide  down  a  trough.  Not 
more  than  1  ft.  thickness  should  be  laid  at 
one  time,  and  it  should  be  lightly  rammed  to 
consolidate  it.  It  was  formerly  the  custom 
to  specify  that  it  should  be  thrown  from  a 
height  of  not  less  than  10  ft.,  but  it  was  found 
that  this  caused  all  the  large  stuff  to  go  to  the 
bottom,  and  where  any  of  that  previously  laid 
had  begun  to  set  it  caused  disintegration.  Each 
batch  of  concrete  should  be  used  within  one 
hour  of  mixing  and  should  not  be  disturbed 
afterwards.  In  important  works  the  voids  in  the 
aggregate  should  be  carefully  measured  in  order 
to  ensure  that  the  mixture  shall  be  in  the  best 
proportions  to  secure  final  solidity.  This  is 
done  by  taking  a  zinc-lined  box  of  given 
capacity  with  an  outlet  tap  in  the  bottom, 
filling  it  up  with  an  average  sample  of  the 
aggregate,  then  filling  with  water  and  making 
up  the  water  to  the  level  of  the  top  as  it  soaks 
into  the  material,  then  running  off  and 
measuring  the  unabsorbed  water,  which  will 
represent  the  voids  in  the  mass.  For  machine- 
mixing  there  are  two  classes  of  apparatus,  the 
continuous  mixers  and  the  batch  mixers ;  the 
latter  are  the  better  type.  Machine-mixing  is 
only  profitable  on  large  jobs  and  then  the  cost 
is  much  reduced.  Some  authorities  recom- 
mend that  the  cement  and  sand  should  be 
made  into  mortar  before  mixing  with  the 
aggregate,  but  the  preliminary  dry  mixing  of 
all  the  materials  is  more  usual. 

LAYING  PROMENADES.  —  After  paring  the 
surface  to  a  level  and  filling  and  ramming 
any  soft  places  with  ashes  or  dry  brick 


M.S.E. 


rubbish,  a  layer  of  3  in.  of  broken  brick 
should  be  put  down  and  rolled  to  a  level 
surface,  well  watered,  and  then  the  concrete 
laid  in  portions  10  ft.  or  12  ft.  square,  each 
portion  divided  from  the  adjoining  one  by  a 
wood  strip,  or,  better  still,  a  strip  of  sheet- 
iron,  smeared  with  soft  soap,  which  can  be 
more  easily  withdrawn.  These,  which  are 
known  as  expansion  boards,  are  removed  as 
soon  as  the  concrete  has  set,  and  the  joint  is 
then  grouted  up  if  too  wide  to  leave.  This 
method  is  generally  effective  in  preventing 
the  unsightly  cracks  which  so  disfigure  some 
pavements.  The  chief  point  is  to  have  the 
cement  thoroughly  air-slaked  before  use  and 
to  see  that  it  is  neither  over  limed  nor  over 
clayed.  Neat  cement  floating  should  be 
applied  to  the  surface  while  the  concrete 
is  still  moist,  to  secure  proper  adhesion. 

CONCRETE  IN  HEAVY  WORK. — In  concrete 
dams  and  heavy  walls,  engineers  require  the 
cement  to  be  as  slow  setting  as  it  can  be 
made  without  detracting  from  its  strength, 
so  that  initial  stresses  may,  as  far  as  possible, 
be  avoided  by  the  mass  being  able  to  adjust 
itself  before  it  becomes  too  rigid.  H.  A. 

Condensers. — (See  "  STEAM  ENGINES"  and 
"  INDICATORS.") 

Condensing.  —  Condensers  are  of  two 
principal  classes,  viz.,  jet  condensers  and 
surface  condensers.  The  jet  condenser  con- 
sists of  an  iron  chamber  of  almost  any  con- 
venient form  in  which  the  exhaust  steam  from 
the  engine  cylinders  and  the  cold  water  spray 
which  is  injected  to  meet  and  condense  the 
incoming  steam  may  be  freely  mixed.  The 
bottom  of  the  chamber,  or  "  hot-well,"  in 
which  the  condensed  water  accumulates,  is 
in  communication  with  an  air  pump  (which 
may  be  worked  from  the  engine  piston  rod), 
the  object  of  which  is  to  draw  off  the  water  and 
any  air  or  vapour  contained  in  the  chamber. 
From  the  hot-well  the  water  is  returned 
by  means  of  a  suitable  feed-pump  to  the 
boiler,  thus  securing  a  considerable  thermal 
advantage  over  the  use  of  cold  feed.  The 
steam  inlet  pipe  into  the  condenser  consists 
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of  a  plain  pipe  entering  at  the  top  of  the 
condenser,  and  the  cold  spray  is  injected 
through  a  perforated  pipe  or  rose  carried  well 
into  the  centre  of  the  condenser  so  that  the 
water  may  be  well  distributed  and  the  steam 
on  entry  immediately  condensed.  The  jet 
condenser  is  made  of  about  one-third  the 
capacity  of  the  cylinders  exhausting  into  it. 
In  the  surface  condenser  the  cooling  water 
and  the  steam  do  not  come  into  contact,  but 
are  separated  from  it  by  the  large  surface  of 
a  number  of  small  metal  tubes  contained  in 
an  outer  casing  of  cast  iron.  The  cooling 
water  circulates  through  the  tubes,  the  exhaust 
steam  is  condensed  around  them,  and  the 
resulting  hot  water  is  removed  by  the  air- 
pump  to  the  hot-well,  from  which  a  feed- 
pump delivers  it  back  to  the  boiler.  Where 
surface  condensers  are  used  in  connection 
with  waterworks  pumping  plant,  it  is  unneces- 
sary to  have  a  separate  circulating  pump  to 
force  the  cooling  water  through  the  condenser, 
as  the  water  pumped  by  the  main  engines 
may  be  made  to  circulate  through  the 
condenser.  Owing  to  the  quantity  thus 
passing  through,  the  water  is  not  heated 
to  any  appreciable  extent. 

The  'advantages  of  condensing  are  two-fold. 
In  the  first  instance  the  engine  has  the 
advantage  of  exhausting  into  a  partial  vacuum 
of  say  27  or  28  in.  instead  of  against  the 
atmospheric  pressure,  and  the  fuel  consump- 
tion is  also  economised  by  the  return  of  hot 
feed  to  the  boiler  instead  of  cold.  For  surface 
condensers  allow  a  tube  surface  of  ^  sq.  ft. 
to  -J*Q  sq.  ft.  per  pound  of  steam  condensed 
per  hour  for  circulating  water  not  exceeding 
65°  F.  at  inlet,  or,  another  rule  is  a  tube 
surface  of  1  sq.  ft.  to  1'8  sq.  ft.  per  I.H.P. 
with  tubes  f  in.  or  f  in.  diameter  and 
2Xo  in.  thick.  (See  also  articles  "  INDICATOR  " 
and  "  STEAM  ENGINE.") 

Conder's  Sulphate  of  Iron  Process  of 
Sewage  Purification.  —  This  system  was 
advocated  by  the  late  F.  E.  Conder,  M.I.C.E., 
who  proposed  that  a  solution  of  iron  should 
ba  added  to  the  sewage  of  each  house  by  the 


use  of  an  instrument  called  a  "ferrometer." 
A  small  stream  of  water  flows  through  the 
ferrometer,  dissolves  the  sulphate  of  iron,  and 
carries  it  into  the  sewers.  A  slice  of  lemon 
is  placed  weekly  in  the  instrument  to  add  a 
vegetable  acid.  It  was  also  proposed  to  place 
trays  of  sulphate  of  iron  in  the  street  man- 
holes, the  chemical  being  dissolved  by  a  small 
stream  of  water.  The  system  has  been  tried 
upon  a  small  scale  at  Chichester  Barracks 
and  in  Bermuda  with  satisfactory  results,  but 
is  not  suitable  for  dealing  with  the  sewage  of 
a  town.  The  cost  of  installation  and  royalty 
is  put  at  about  £36  per  100  people,  and  of 
chemicals  at  6d.  per  head  per  annum.  The  cost 
of  labour,  attendance,  and  the  removal  of  the 
resulting  deposits  from  sewers  would  appear  to 
be  a  bar  to  the  extended  use  of  such  a  system. 

Condy's  Fluid.—"  Condy's  Green  Fluid  " 
is  a  strongly  alkaline  solution  of  sodium 
manganate,  Na2Mn04,  with  much  sodium 
chloride  and  some  permanganate.  The 
"Ked  Fluid"  is  a  purer  sodium  permangan- 
ate. Crystallised  potassium  permanganate, 
K2Mn208,  which  is  pure  and  fairly  cheap, 
is  preferable  to  either,  but  as  a  disinfectant 
it  is  still  very  costly,  and,  moreover,  unsafe, 
on  account  of  its  almost  immediate  destruc- 
tion by  organic  matter.  The  writer  had 
unfavourable  results  with  street  watering.1 
(See  "  DISINFECTANTS.") 

Connections — House  Drains  to  Sewers. 

— That  portion  of  the  drainage  of  a  building 
which  lies  between  the  disconnecting  trap  of 
the  drain  at  its  outlet  and  the  public  sewer. 
This  drain  is  frequently  laid  by  the  local 
authority,  as  it  involves  the  tapping  and 
connecting  up  to  the  sewer  and  the  taking 
up  of  part  of  the  highway.  The  cost  of  the 
work,  however,  falls  upon  the  owner  of  the 
house. 

Conservancy  System. — The  conservancy 
system  of  excrement  disposal  is  that  in  which 
the  nightsoil  is  retained  in  pans  or  pits,  instead 

1  "  Sanitary  Record,"  July  27th,  1900. 


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MUNICIPAL  AND   SANITABY  ENGINEERING. 


CON 


of  being  carried  away  in  pipes,  as  in  the 
"Water-carriage  System."  In  some  cases 
the  dejecta  are  received  in  large  built  pits, 
into  which  the  household  ashes  are  sometimes 
thrown,  and  which  are  emptied  periodically. 
Another  and  better  plan  is  to  use  pails  or 
pans,  which  are  removed  and  cleansed  at 
short  intervals.  In  earth-closets  the  dejecta, 
as  deposited,  are  covered  with  a  little  dry 
earth.  The  conservancy  system  is  largely 
employed  in  country  districts,  the  nightsoil 
being  used  as  a  manure.  It  also  survives  in 
a  number  of  large  towns  in  the  Midlands  and 
North  of  England,  and  in  the  Colonies,  but 
it  is  unfavourably  regarded  by  the  health 
authorities,  and  its  supersession  by  the  water- 
carriage  system  is  merely  a  question  of  time. 
The  main  point  in  its  favour  is  that  it  con- 
serves and  returns  to  the  soil  the  manurial 
constituents  of  the  excreta.  On  the  other 
hand,  the  retention  of  faecal  matter  near 
houses  is  offensive,  and  even  dangerous,  more 
especially  in  view  of  the  action  of  flies  in 
conveying  infective  material  from  the  closets 

to  the  larder. 

A.  J.  M. 

Contact  Beds,  Bacterial. — (See  "  SEWAGE 
DISPOSAL.") 

Conveniences,  Underground.  —  Acts  of 
Parliament — Points  to  be  Noted — Site — Exca- 
vation —  Walls  —  Drainage  —  Roof  —  Staircase 
-  Ventilation  —  Sanitary  Fittings  —  Plumbing, 
&c.  —  Attendant's  Cabin  —  Framing  —  Locks  — 
Lighting — Cost. 

ACTS  OF  PARLIAMENT. — Power  to  borrow 
money  for  the  purpose  of  providing  under- 
ground conveniences  and  lavatories  within  the 
metropolis  is  contained  in  sect.  105  (2)  (a)  of 
the  Public  Health  (London)  Act,  1891,  and, 
in  the  provinces,  the  Public  Health  Act,  1875, 
sect.  39,  gives  an  urban  authority  power,  if 
they  think  fit,  to  provide  and  maintain  con- 
veniences, while  the  Public  Health  Acts 
Amendment  Act,  1890,  sect.  20,  gives  the 
urban  authority  power,  if  they  think  fit,  to 
make  regulations  for  the  management  thereof, 
and  to  make  bye-laws  as  to  the  decent  conduct 


of  persons  using  same.  Also  the  urban 
authority  may  let  the  convenience  for  a  term 
not  exceeding  three  years,  or  may  charge  such 
fees  for  the  use  of  the  water  closets  as  they 
may  think  proper. 

POINTS  TO  BE  NOTED. — When  choosing  a  site 
for  an  underground  convenience  (and  only 
such  are  referred  to  in  this  article)  the 
following  points  should  be  considered: — 
1.  Central  position  with  regard  to  the  necessity 
for  such  a  structure.  2.  Position  with  regard 
to  lines  of  traffic.  3.  Available  depth  with 
regard  to  sewers  and  risk  of  flooding  when 
sewers  are  surcharged.  4.  Stability  of  founda- 
tion. 5.  Absence  of  gas,  water,  and  other 
mains  or  facility  of  diverting  them  if 
encountered. 

SITE. — Persons  requiring  the  services  of 
such  a  structure  usually  seek  them  in  large 
open  spaces,  and  since,  owing  to  their  con- 
struction, they  form  a  useful  landing-place  or 
refuge  among  the  traffic,  it  is  in  keeping  that 
the  position  should  be  chosen  with  great  care, 
and  that  they  should  be  so  placed  as  to  be 
en  route  from  the  corner  of  one  street  to  the 
corner  of  another,  and  yet  allow  at  least  two 
lines  of  traffic  to  pass  along  each  of  their  sides, 
and  their  proximity  to  tramway  lines  should 
not  be  less  than  9  ft.  6  in.  to  the  nearest  rail. 

EXCAVATION. — In  forming  the  excavation 
great  care  should  be  taken  in  view  of 
encountering  the  mains  belonging  to  the 
various  gas,  water,  and  other  companies,  as 
damage  to  same  might  unduly  prolong  the 
work,  and  cause  an  unnecessary  interference 
with  the  street  traffic.  The  question  of  the 
existence  of  such  mains  should  be  fully  gone 
into  before  the  scheme  has  finally  been 
decided  on,  as  it  sometimes  happens  that  a 
diversion  may  either  be  impossible  or  very 
costly,  and  the  subsequent  alteration  of  the 
convenience  render  it  the  less  commodious 
and  inconvenient  in  administration.  When 
arranging  details  prior  to  commencing  the 
work,  it  will  be  found  convenient,  in  a  work  on 
so  restricted  a  space,  to  have  all  material 
delivered  at  one  end  and  the  debris  carted 
away  at  the  other.  Also  rather  than  extend 


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the  area  of  the  enclosure  to  provide  for  a  fore- 
man's office  and  so  impede  the  traffic,  it  may 
be  found  possible  to  erect  it  on  a  low  scaffold 
overhead.  The  excavation  should  be  the  neat 
width  of  the  outside  walls,  and  no  footings 
should  of  course  project  beyond  the  outside 
face  of  the  outer  walls.  The  depth  of  concrete 
under  the  walls  should  be  12  in.  to  18  in., 
according  to  the  local  conditions  of  the  sub- 
soil, and  project  beyond  the  internal  face  of 
the  wall  for  at  least  12  in. 

WALLS. — The  walls  are  generally  constructed 
of  an  outer  thickness  of  12  in.  of  Portland 
cement  concrete,  and  faced  on  the  inside  with 
14  in.  or  18  in.  of  brickwork,  between  which 
and  the  concrete  backing  is  a  vertical  damp- 
proof  course  of  asphalte,  with  also  one  laid 


flnsmof/t  lighlt 


sfwwiny 
method  of  Vwldcdiori 

FIG.  1. 

horizontally.  Occasionally  the  whole  of  the 
wall  is  composed  of  concrete,  which  should  be 
formed  in  two  thicknesses,  with  the  vertical 
damp-proof  course  inserted  as  previously 
mentioned.  The  inside  face  of  the  walls 
where  constructed  of  brickwork  is  often  of 
glazed  bricks,  but  as  these  have  to  be  fre- 
quently cut  for  fixing  pipes,  plugs  and  hold- 
fasts, the  subsequent  making  good  often 
presents  an  untidy  finish.  It  is  preferable  to 
cover  the  rough  brickwork  or  concrete  with 
§  in.  tiles  of  brick  pattern,  thus  obtaining  a 
finer  joint  than  with  bricks,  and  a  better  finish 
may  be  obtained  to  soffits  and  scribing  than 
by  the  use  of  glazed  bricks.  Some  con- 
veniences have  been  faced  with  opal  glass  tiles 
as  supplied  under  various  trade  names  and  of 
different  makes.  The  use  has  been  attended 
with  more  or  less  success.  It  is  thought  by 
some  engineers  that  the  vibration  of  the  street 
traffic  has  a  tendency  to  crack  the  tiles, 


although  the  fineness  of  the  joints,  choice  of 
colour,  and  ease  with  which  they  can  Jbe  cut 
to  fit  around  awkward  corners  is  an  argument 
in  their  favour.  The  floor  should  be  con- 
structed of  concrete,  and  covered  with  tiles. 

DRAINAGE. — The  drainage  of  a  convenience 
is  a  matter  of  supreme  importance.  No  such 
structure  should  be  built  which  cannot  allow 
of  an  adequate  fall  in  the  drain  from  the 
interceptor  to  the  sewer,  and  also  be  at  such  a 
relative  level  above  the  sewer  that  no  back 
flow  may  occur  from  flooding,  due  to  rainfall, 
rise  of  tide,  &c.  There  are  two  possibilities 
likely  to  occur  with  every  convenience,  namely, 
the  risk  of  flooding,  due  to  (1)  the  flow  in 
the  sewer,  and  (2)  stoppage  in  the  inter- 
ceptor, and  to  deal  with  this  until  the  outlet 
of  the  drain  may  be  free  there  must  be  con- 
structed a  storage  chamber  under  the  floor  of 
the  convenience  of  a  size  calculated  to  be 
sufficient  to  retain  the  sewage  until  the  diffi- 
culty has  been  removed.  The  storage  capacity 
of  the  chambers  in  the  convenience  illustrating 
this  article  is  represented  by  two  connected 
tanks,  each  3  ft.  deep,  and  holding  together  1,800 
gallons,  and  serving  to  retain  the  water  from 
9  w.c.'s,  11  urinals,  3  urinettes,  and  4  lavatory 
basins.  Of  course  when  the  outward  flow 
from  the  drain  is  restricted,  the  attendants 
minimise  the  use  of  the  wash-basins  and  the 
automatic  flush  to  the  urinals  as  much  as 
possible.  The  chambers,  which  are  practi- 
cally large  manholes,  may  be  faced  with 
glazed  bricks,  and  are  formed  on  the 
invert,  with  white  glazed  half  round  pipes, 
and  cement  benchings.  One  chamber  should 
be  constructed  in  each  of  the  male  and 
female  compartments,  and  each  w.c.  connected 
thereto  direct.  The  urinals  and  lavatories 
may  be  grouped  in  sets,  and  each  set  also 
connected  direct.  A  sparge  pipe  should  be 
fixed  around  each  chamber  at  the  top,  and 
connected  with  the  water  supply,  and  be  under 
the  control  of  the  attendant — this  is  to  wash 
down  the  sides  of  the  chamber  after  the 
retained  waste  water  flows  off.  As  this  pipe 
will  be  at  the  furthermost  extremity  of  prob- 
ably a  shallow  manhole,  it  will  be  difficult  of 
84 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


CON 


access;  therefore  it  should  be  of  copper,  as 
this  is  not  liable  to  rust  either  inside  or  out. 
Air-tight  manhole  covers  should  be  provided  to 
each  chamber,  and  it  is  usual  to  make  pro- 
vision for  tiles  to  be  let  in  the  top  to  match 
the  general  tiling  of  the  floor.  The  waste 
from  the  w.c.'s,  lavatories,  £c.,  should  dis- 
charge into  a  manhole  after  leaving  the  storage 
chamber  and  before  passing  through  the 
interceptor.  A  penstock  should  be  placed  on 
this  pipe  so  as  to  prevent  the  waste  from 
entering  the  manhole,  when  required,  thus 
impounding  it  in  the  storage  chamber.  The 
reason  for  this  being  that  in  case  of  the 


his  chambers  have  become  so  filled  that  they 
overflow  on  to  the  floor  of  the  convenience. 
To  cope  with  this  the  author  has  devised  a 
ball  and  lever  arrangement  fixed  in  one  of 
the  chambers,  and  so  made  that  when  the 
ball  floats  owing  to  rise  of  water  it  will  raise 
a  rod  connected  with  an  electric  bell  which 
will  act  as  a  warning  to  the  attendant. 

ROOF. — The  roof  is  the  one  portion  of  the 
structure  which  will  probably  give  a  consider- 
able amount  of  trouble  and  annoyance  to  those 
concerned,  either  from  leakage  due  to  outside 
moisture  or  from  sweating  due  to  condensation 
of  internal  moisture.  The  convenience  should 


t^CA-'LlAJri/ 

r.  ,  .  .  f  .  , 

•r-r-£  f  ^ 

/JV^z/*  of  -Feet  . 

FIG.  2. 

interceptor  being  stopped,  the  waste  from  the 
w.c.'s,  lavatories,  &c.,  may  be  retained,  and 
the  manhole  pumped  dry  so  as  to  allow  the 
obstruction  to  be  removed  from  the  inter- 
ceptor. A  penstock  should  also  be  fixed  over 
the  interceptor,  so  that  it  may  be  closed  down 
at  a  time  of  flood  in  the  sewer,  to  prevent  the 
sewage  finding  its  way  either  into  the  manhole 
or  the  convenience.  This  is  extremely  useful 
at  night,  if  the  penstock  is  closed  down  before 
the  attendant  leaves.  The  manhole  containing 
these  two  penstocks  should  be  accessible  only 
from  the  surface  of  the  ground  outside.  There 
are  occasions  when  the  sewer  may  be  in  flood, 
or  the  interceptor  be  stopped,  and  the  attendant 
be  unaware  of  the  fact  until  he  discovers  that 


85 


be  so  designed  that  the  roof  may  be  about 
10  ft.  6  in.  above  the  floor.  The  construction 
of  the  roof  should  be  of  wrought  iron  or  steel 
joists  carrying  prismatic  lights,  and  care 
should  be  taken  that  a  sufficient  gradient  is 
given  to  the  frames  containing  these  lights 
to  throw  the  water  off  as  quickly  as  possible. 
Large  areas  of  prismatic  lights  are  subject  to 
considerable  expansion  and  contraction  during 
the  varying  temperatures,  and  as  this  is  the 
main  cause  of  leakages,  arrangement  should 
be  made  whereby  the  lights  should  be  divided 
into  sections  and  so  reduce  the  ultimate  con- 
traction and  expansion.  The  joints  between 
the  frames  should  be  made  with  a  pliable 
cement.  Should  any  part  of  the  convenience 


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be  under  the  carriageway,  the  design  of  the 
roof  will  require  more  attention  than  other- 
wise, as  provision  must  be  made  for  heavy 
motor  traffic.  The  construction  in  this  case 
might  consist  of  steel  girders  supporting  brick 
arches,  with  the  crown  and  haunches  filled  in 
with  concrete,  or  reinforced  concrete  might  be 
used  instead  and  the  top  of  the  concrete  then 
be  paved  with  wood  blocks  or  asphalte  to  form 
the  surface  of  the  road.  That  part  of  the  roof 
which  contains  the  prismatic  lights  and  is  not 
available  for  vehicular  traffic  should  be  formed 
a  step  higher  than  the  road  and  surrounded 
with  a  wide  granite  kerb,  heavy  cast-iron  guard- 
posts,  and  granite  spur  stones.  Various  devices 
have  been  tried  to  deal  with  the  condensation 
of  the  moist  internal  air  in  relation  to  its 
corrosive  action  on  the  iron-work.  The  most 
successful  method  is  to  cover  the  paint  and 
varnish  with  fine  cork  dust  while  the  varnish 
is  still  wet. 

STAIRCASE. — The  rules  covering  the  en- 
trances and  exits  are  such  as  would  suggest 
themselves  in  any  ordinary  building.  If  two 
staircases  cannot  be  provided,  one  for  the 
entrance  and  the  other  for  the  exit,  the  width 
of  the  single  stair  should  be  sufficient  to  allow 
of  two  persons  passing  one  another.  The  top 
step  should  be  so  placed  as  not  to  come  within 
a  distance  of  about  3  ft.  from  the  carriage- 
way, so  as  to  prevent  a  person  stepping  directly 
in  front  of  the  traffic.  The  staircase  should 
be  formed  with  easy  steps  and  as  few  winders 
as  possible,  but  owing  to  their  narrowness  and 
the  great  amount  of  traffic,  the  treads  will  be 
subject  to  considerable  wear,  unless  some  of 
the  various  patent  treads  are  used,  such  as 
are  to  be  found  on  the  market,  but  whichever 
form  is  adopted  they  should  be  so  fixed  as 
to  be  capable  of  renewal  expeditiously  and 
without  much  damage  to  the  surrounding 
work.  A  considerable  amount  of  water  will 
flow  down  the  steps  both  during  rain  and 
when  washing  down.  A  channel  with  a 
grating  over  it  should  therefore  be  fixed  at 
the  bottom,  having  a  pipe  connected  to  the 
manhole  so  as  to  carry  away  any  water  that 
may  flow  down.  The  staircases  are  usually 


86 


protected  with  ornamental  pailings  about  5  ft. 
high,  having  a  padlocked  gate  at  the  entrance. 
To  screen  the  interior  of  the  convenience  it  is 
customary  to  cover  the  pailings  with  wired 
rough  plate  glass.  Owing  to  conveniences 
being  frequently  burgled  at  night-time,  either 
for  the  sake  of  the  brass  fittings  or  the  money 
in  the  automatic  locks,  it  has  been  found 
necessary  to  construct  a  collapsible  gate  at  the 
foot  of  the  staircase  and  also  a  horizontal 
grating,  level  with  the  top  rail  of  the  palings, 
having  a  portion  so  made  as  to  slide  backward 
and  forwards,  and  when  drawn  towards  the 
gate  and  locked  it  forms  an  effectual  cage, 
entirely  covering  in  the  staircase  and  pre- 
venting people  climbing  over  for  unlawful 
purposes. 

VENTILATION. — Various  methods  are  adopted 
to  ventilate  the  inside  of  the  convenience.  A 
ventilating  column  may  be  fixed  on  the  wall 
dividing  the  male  from  the  female  sections, 
having  a  revolving  fan,  driven  by  electricity 
or  water.  In  the  latter  case  the  waste  water 
may  be  used  for  flushing  the  urinals.  The 
column  is  generally  utilised  as  a  lamp-post 
for  lighting  purposes,  and  may  be  of  an 
ornamental  character.  Another  method  of 
ventilating  may  be  by  a  continuous  iron 
grating  about  6  in.  or  9  in.  wide  fixed  level 
with  the  top  of  the  prismatic  lights,  thus 
forming  an  opening  all  round  the  structure. 
Ptain  and  dirt  which  will  go  through  are 
caught  in  a  heavy  pattern  cast-iron  gutter, 
and  the  water  is  delivered  into  the  drains 
through  a  square  section  rainwater  pipe, 
chased  into  the  wall.  Splashing  of  water  and 
a  direct  line  of  vision  into  the  convenience 
from  the  outside  is  prevented  by  a  6  in.  to  9  in. 
width  of  zinc  or  sheet  iron  placed  at  a  suitable 
angle  so  as  to  drip  into  the  gutter.  Fre- 
quently both  methods  of  ventilation  are  used 
in  conjunction  with  one  another. 

SANITARY  FITTINGS. — The  sanitary  fittings 
for  a  convenience  are  made  in  many  designs 
and  of  various  shapes,  and  it  must  be  left  to 
the  fancy  of  the  engineer  to  choose  for  himself. 
It  is  preferable  to  adopt  a  design  that  can  be 
easily  cleaned  in  all  its  parts  and  renewed  if 


CON 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


CON 


broken.  The  urinals  may  be  formed  with  an 
open  channel  attached,  the  latter  being  covered 
with  a  galvanised  or  brass  grating.  The 
division  between  each  stall  may  be  St.  Anne's 
or  other  marble  or  even  polished  and  oiled 
slate,  or  it  may  be  of  the  same  material  and 
colour  as  the  urinal  itself,  and  the  urinals 
should  be  24  in.  from  centre  to  centre.  The 
w.c.  pans  should  be  quite  self-cleansing,  with 
one  flush,  the  "  wash  down  "  type  being  the 
best.  The  w.c.  compartments  generally 


the  opposite  direction  to  a  w.c.  Some  of  the 
patterns  also  have  a  perforated  grating  on  the 
trapped  outlet  instead  of  the  free-way  of  a  w.c. 
trap.  As  a  rule  the  purpose  and  method  of 
using  a  urinette  is  not  understood  by  those 
who  enter  a  women's  convenience,  and  they 
are  frequently  put  to  the  purpose  of  a  w.c., 
hence  their  existence  becomes  either  useless 
or  a  nuisance.  In  many  of  the  conveniences 
where  urinettes  have  been  fixed,  the  usual 
wooden  door  has  been  dispensed  with,  and 


-Plcuz 


Vertical  damp  f>r°°f  ccu,rs0 

RJ "ATlgel  M/HST.CE.- 


of  Feet . 

FlG.  3. 


measure  about  6  ft.  by  3  ft.,  and  are  divided 
by  marble  divisions  1^  in.  or  1J  in.  thick  and 
7  ft.  to  7  ft.  6  in.  high.  An  addition  to  the 
women's  section  has  been  made  recently  in 
the  form  of  a  "  Urinette."  This  has  been  an 
attempt  to  do  away  with  the  objection  that  a 
man  may  use  a  urinal  free,  while  a  woman 
has  to  pay  for  a  similar  purpose.  These 
urinettes  are  in  form  similar  to  a  w.c.  pedestal ; 
some  patterns  are  narrower  than  the  w.c.  pan, 
the  intention  being  that  the  users  may  stand 
over  it  with  their  face  towards  the  wall  or  in 


waterproof  sheeting  hung  as  a  curtain  in  place 
thereof. 

PLUMBING,  &c. — The  plumbing  and  fittings 
should  be  of  the  best  and  simplest  of  their  kind. 
The  water  supply  to  each  section  should  be 
separately  under  control  to  enable  any  par- 
ticular part  to  be  shut  off  for  repairs.  A  tap 
should  be  provided  inside  each  of  the  con- 
veniences with  nozzle  for  a  hose  pipe,  likewise 
a  hydrant  should  be  fixed  outside  and  suited 
to  the  same  hose  pipe  for  washing  down  the 
roof  and  steps.  Hot  water  should  be  provided 


87 


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ENCYCLOPEDIA   OF 


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in  each  of  the  lavatories  by  a  geyser.  Also 
the  attendant  should  have  a  stove  for  warming 
and  cooking. 

ATTENDANT'S  CABIN. — The  attendant's  cabin 
should  be  made  as  large  and  airy  as  possible, 
and  so  placed  as  to  command  a  view  of  the 
whole  of  the  convenience  and  the  staircases, 
and  be  provided  with  a  wooden  floor.  Much 
more  space  ought  to  be  given  to  the  attendant 
than  is  usually  done.  We  frequently  find  that 
he  is  provided  with  so  small  a  compartment 
that  he  experiences  the  greatest  discomfort 
when  in  it. 

FRAMING. — The  general  framing,  doors,  &c., 
of  the  inside  should,  for  preference,  be  of  teak, 
as  owing  to  its  nature  it  is  non-absorbent  and 
proof  against  damp.  The  w.c.  doors  may  be 
made  so  as  to  leave  a  few  inches  of  space  at 
the  bottom  above  the  ground,  or  the  bottom 
panel  may  be  in  the  form  of  louvres,  so  as  to 
allow  a  current  of  air  to  circulate  within. 
Items  not  to  be  forgotten  are  the  provision  in 
the  w.c.'s  of  toilet-paper  holders  and  hooks  for 
coats.  In  the  lavatories — mirrors,  towel  rails, 
coat-hooks,  brushes  and  combs.  In  the  atten- 
dant's cabin — cupboards  for  personal  articles, 
storage  for  towels,  soap,  &c.,  and  safe  drawers 
for  money,  &c.  A  speaking  tube  should  con- 
nect the  attendant  in  the  male  and  female 
sections. 

LOCKS. — The  locks  to  the  w.c.  doors  may  be 
either  of  automatic  penny-in-the-slot  type,  or 
else  locks  having  a  registering  number,  in 
which  case  the  user  pays  the  attendant  and 
the  lock  indicates  the  number  of  times  the 
door  has  been  opened.  Bent  coins  have  caused 
considerable  inconvenience  and  damage  to  the 
former  type  of  lock. 

LIGHTING. — If  the  illumination  of  the  con- 
venience is  by  gas,  care  should  be  taken  not 
to  place  the  brackets  too  close  to  the  prismatic 
lights,  as  the  latter  have  been  known  to  chip 
owing  to  the  heat.  The  placing  of  the  lights 
over  the  w.c.'s  may  be  economically  done  by 
making  one  bracket  serve  two  closets.  Should 
electricity  be  used,  it  may  be  found  convenient 
to  so  arrange  the  switches  which  are  controlled 
from  the  cabin  that  certain  of  the  lights  may 


be  switched  off  when  not  required.  The  stair- 
cases should  be  well  lighted  and  an  illuminated 
sign  is  sometimes  fixed  over  the  entrance.  It 
is  also  desirable  if  the  convenience  be  lit  by 
electricity  to  also  have  at  least  one  gas  bracket 
available  in  case  of  the  current  failing. 

COST. — The  convenience  illustrating  this 
article  cost,  without  diversion  of  mains,  ,£2,500, 
or  '6s.  6d.  per  foot  cube.  R.  J.  A. 

"  Coombs  "   Pneumatic  Ejector.— (See 

"  EJECTORS.") 

Cosham  Precipitating  Tank.  -  -  This 
form  of  preliminary  preparation  tank  of  the 
"Natural"  Purification  Company  was  first 
adopted  at  Nuneaton.  It  may  be  constructed 
either  on  a  circular  or  rectangular  plan,  and 
consists  of  a  series  of  seven  or  eight  separate 
compartments  through  which  the  sewage 
flows  successively  on  its  way  to  the  outlet. 
The  communications  between  the  compart- 
ments are  formed  by  "  flocculent  flues  "  or 
submerged  exits,  the  object  of  which  is  to 
hold  back  floating  matter.  These,  together 
with  a  number  of  cross  walls,  assist  the 
precipitation  within  the  tank  and  economise 
the  chemicals  employed.  The  sludge  is 
removed  from  the  bottom  of  the  tank  by  a 
siphon  terminating  a  little  below  the  top 
water  level  within  the  tank. 

Cremator  (Jones'). — This  consists  of  a 
small  independent  high  temperature  furnace 
used  in  connection  with  town  refuse  destructors 
for  the  purpose  of  cremating  and  rendering 
harmless  the  objectionable  fumes  known  as 
the  empyreumatic  vapours  which  arise 
during  the  earlier  stages  of  the  process  of 
burning  town's  refuse.  It  was  introduced  in 
1885  by  Mr.  C.  Jones,  M.I.C.E.,  of  Baling, 
but  since  that  date  considerable  advances  have 
been  made  in  the  process  of  disposal  of  refuse 
by  burning  mainly  by  the  adoption  of  high 
temperature  destructors  of  greatly  improved 
design,  thus  rendering  the  employment  of  an 
independent  cremator  unnecessary.  (See 
"  DESTRUCTORS.") 


88 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


CRE 


Crematoria  and  Columbaria.  —  General 
Survey —  Catafalque  —  Incinerating  Chamber — 
Chimney  Shaft — Furnaces — Columbaria — Site  of 
a  Crematorium — Cost  of  Crematoria. 

In  the  general  arrangement  of  the  plan  of 
these  buildings  it  is  of  the  utmost  importance 
that  due  regard  be  given  to  the  relative 
positions  of  the  chapel  and  the  incinerating 
chamber,  so  that  the  coffin  can  be  transported 
from  the  chapel  to  the  crematory  as  quickly 
as  possible.  The  chapel  or  hall  should  be 
planned  with  a  minimum  floor  area  of  1 ,200 
super,  feet.  It  will  be  found  that  this  is  the 
least  permissible,  for  when  the  catafalque  and 
necessary  seating  is  provided  there  will  remain 
little  waste  space.  Provision  should  be  made 
in  the  chapel  for  the  reception  of  urns ; 
they  may  be  stored  in  niches  in  the  walls,  in 
the  floor,  or  in  the  sides  of  the  catafalque.  In 
some  cases  a  columbarium  is  provided  under 
the  chapel  in  the  basement.  This  is  found  in 
the  Liverpool  Crematorium.  A  system  of 
electric  inter-communication  between  the 
chapel  and  the  incinerating  chamber  is 
necessary ;  a  bell-push  placed  either  on  the 
clergy's  desk,  or  in  the  floor  near  it.  This  is 
provided  so  that  he  may  inform  the  engineer 
in  charge  when  the  moment  arrives  for  the 
body  being  removed  from  the  chapel  to  the 
cremating  chamber. 

THE  CATAFALQUE. — The  catafalque  or  table 
upon  which  the  coffin  is  placed  during  the 
service  should  be  situated  near  the  cremating 
chamber.  In  most  of  the  English  crematoria 
it  is  situated  so  as  to  project  longitudinally 
into  the  chapel.  This  position  has  many  dis- 
advantages. It  is  far  preferable  to  place  the 
cremating  chamber  at  the  side  of  the  chapel, 
so  that  the  coffin  passes  out  at  the  side,  and 
the  opening  between  the  two  apartments  is  not 
facing  those  who  are  assembled  to  witness  the 
last  rites. 

The  catafalque  in  general  use  is,  in  size, 
about  12  ft.  long,  3  ft.  Sin.  wide,  and  4  ft.  high. 
The  top  is  fitted  with  an  apparatus  worked  by 
means  of  an  endless  chain,  which  conveys  the 
coffin  from  the  catafalque  to  the  carriage  in  the 
cremating  chamber.  The  coffin  is  transported 


to  the  furnace  upon  a  carriage  fitted  with  the 
same  apparatus.  The  opening  in  the  wall 
through  which  the  coffin  passes  should  be  the 
full  width  of  the  catafalque,  and  about  2  ft.  6  in. 
to  3ft.  high.  It  should  be  fitted  with  a  pair  of 
wrought-iron  doors,  grills,  or  curtains. 

INCINERATING  CHAMBER. — The  incinerating 
chamber,  which  adjoins  the  chapel,  is  governed 
in  size  by  the  number  and  type  of  furnaces  to 
be  installed.  When  provision  is  made  for  one 
furnace  only,  then  the  chamber  should  have  a 
minimum  width  of  20  ft.  and  25  ft.  in  length.  This 
will  be  found  sufficiently  large  for  any  furnace. 
When  two  or  more  furnaces  are  provided  then 
the  superficial  area  will  be  increased  in  pro- 
portion. The  cremating  chamber  should  be 
well  lighted  and  ventilated,  and  constructed  of 
such  materials  as  will  allow  of  it  being  kept 
perfectly  clean. 

CHIMNEY  SHAFT. — The  chimney  shaft  should 
be  situated  in  as  close  proximity  to  the 
cremating  furnaces  as  possible ;  the  internal 
measurements  at  the  base  being  at  least  2  ft. 
square.  The  shaft  should  be  erected  to  a 
minimum  height  of  60  ft.  A  pilot  fire  is 
necessary  at  the  base  of  the  chimney  shaft  for 
any  fumes  not  consumed  in  the  furnace,  to 
pass  over.  Many  forms  of  pilot  fires  have 
been  constructed,  but,  for  general  purposes,  if 
a  small  grid  is  formed,  having  open  bars  for 
holding  a  small  fire,  it  will  meet  the  purpose 
for  which  it  is  provided.  A  small  iron  door 
and  frame  will,  of  course,  be  provided  for  access 
to  the  pilot  fire. 

FURNACES. — There  are  two  types  of  furnace 
employed  for  burning  human  bodies — the 
reverberatory  and  the  regenerative.  In  the 
former  a  tongue  of  flame  coming  directly  from 
ihe  flue  is  deflected  on  to  the  body.  In  the 
latter,  gas  is  produced  from  coke,  and  then 
burnt  in  the  chamber  where  the  body  is  placed. 
Both  methods  are  equally  effective,  but  the 
latter  furnace  is  much  more  costly  to  con- 
struct. It  lends  itself,  however,  to  a  more 
satisfactory  means  of  collecting  the  ashes, 
and  is  in  keeping  with  popular  sentiment. 
There  are  four  patent  cremating  furnaces  on 
the  English  market,  three  of  which  are  in  use. 


89 


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ENCYCLOPEDIA  OF 


CRE 


They  are  the  "  Simon "  coke  furnace,  the 
"  Tousil  Fradet,"  a  gas  furnace,  and  the 
"  Carbon  Oxide  "  ;  another  patent  furnace  is 
that  of  Messrs.  Goddard,  Masey,  &  Warner, 


FIG.  1. — Design  by  M.  Formege,  Chief  Architect  Paris 
Municipality. 


consists  of  three  chambers,  the  two  lower  of 
which  are  surrounded  by  air  passages.  The 
lower  chamber  contains  a  coke  fire,  and  the 
upper  or  cremating  one  is  that  in  which  the 
body  is  reduced  to  ashes.  The 
fire  is  lit  some  time  before  the 
apparatus  is  to  be  used,  and  is 
supplied  with  air  in  the  usual  way. 
Before  the  introduction  of  the 
coffin  containing  the  body  the  air 
supply  to  the  coke  fire  is  greatly 
restricted,  and  after  the  body  has 
been  placed  in  the  furnace  a 
separate  supply  of  heated  air  is 
introduced.  Owing  to  the  re- 
stricted air  supply  under  the  fire 
the  product  of  combustion  is  largely 
carbonic  oxide,  which  immediately 
on  the  addition  of  hot  air  burns 
into  carbonic  acid.  The  incine- 
rating chamber  is  thus  filled  with 
gas  of  an  intensely  oxidising 
character,  in  a  state  of  incan- 
descence. The  process  occupies 
about  one  hour,  at  the  end  of 
which  time  there  remains  only  the 
residue  of  the  bones,  consisting  of 
grey  pumice-like  fragments.  As 
the  body  is  reduced  to  ashes,  the 
remains  fall  through  the  grid  into 
the  chamber  below.  At  the  com- 
pletion of  the  operation  they  are 
swept  by  an  asbestos  brush  into 
an  urn.  Two  inspection  holes  are 
provided  at  the  head  of  the 
furnace  ;  one  overlooking  the 
chamber  containing  the  body,  the 
other  the  chamber  which  receives 
the  ashes.  These  are  provided  so 
that  the  engineer  in  charge  may 
watch  the  progress  and  so  regulate 
the  working  of  the  furnace  to  suit 
the  progress  of  reduction.  This 
furnace  is  erected  in  two  storeys. 


Messrs.  Henry  Simon  &  Co.'s  furnace,  which 
is  in  use  in  the  principal  crematoria  of  this 
country,  is  made  in  two  distinct  types.  The 
older  one  is  of  the  regenerative  type,  and 


When  this  furnace  is  adopted  it  is  advisable 
to  form  an  opening  in  the  floor  clear  of 
the  same,  so  that  any  expansion  or  con- 
traction which  takes  place  will  in  no  way 


90 


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MUNICIPAL   AND    SANITAEY  ENGINEERING. 


CRE 


affect  the  main  structure.  In  the  later  type 
of  the  "Simon"  furnace  it  is  not  necessary 
to  have  a  basement,  the  whole  being  fixed  on 
one  level.  This  type  is  somewhat  longer  than 
the  former  owing  to  the  firing 
portion  being  at  the  end  instead 
of  below.  With  this  furnace  the 
fuel  used  is  coke  only,  and  the  heat 
is  brought  more  directly  into  con- 
tact with  the  body.  There  is 
consequently  a  saving  in  the  pre- 
liminary heating  of  the  brickwork 
and  flues  previous  to  the  operation. 
The  construction  is  simple,  and  the 
furnace  is  built  to  withstand  the 
contraction  and  expansion  which 
takes  place  in  all  intermittently- 
fired  furnaces.  This  furnace  can 
also  be  arranged,  with  slight  modi- 
fications, for  heating  with  coal  gas. 
The  Carbon  Oxide  Company's 
furnace,  which  is  heated  by  coke, 
is  fixed  in  the  Golder's  Green 
and  Woking  Crematoria.  Little 
information  can  be  obtained  of 
this  furnace,  but  judging  from 
inspection  it  appears  to  work  satis- 
factorily. The  construction  is 
similar  to  those  furnaces  pre- 
viously described.  Messrs.  Tousil, 
Fradet  &  Company's  furnace  is  in 
use  at  the  Leeds  and  Bradford  Cre- 
matoria. This  type  of  furnace  has 
been  in  operation  for  some  years  in 
the  crematoria  at  Paris,  Rouen, 
Rheims,  and  Lyons.  The  heating 
is  performed  by  gas,  introduced 
through  Bunsen  burners  at  the 
rear  of  the  chamber  containing 
the  corpse.  The  products  of  com- 
bustion pass  out  at  the  side  near 
the  front  or  entrance  of  the 
chamber.  The  hot  gases  are  then 
conveyed  along  flues  and  pipes  underneath 
the  furnace  in  such  a  way  as  to  highly 
heat  the  air  supply  to  the  burners,  as  well 
as  a  separate  air  supply  that  is  arranged 
to  enter  the  chamber  at  each  side  of  the 


body  at  the  later  stages  of  the  process, 
when  desiccation  has  been  completed  and 
inflammable  gases  are  being  given  off  from 
the  body.  The  air  supply  to  the  Bunsen 


91 


FIG.  2. — Crematoria,  Portland,  U.S.A. 

burners  is  controllable,  as  is  that  sup- 
plied separately  to  the  sides  of  the  in- 
cinerating chamber.  Messrs.  Tousil,  Fradet 
&  Company  also  use  a  special  mechanical 
apparatus  for  introducing  the  coffin  into  the 


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ENCYCLOPEDIA   OF 


CUL 


incinerating  chamber,  and  for  removing  the 
ashes. 

COLUMBARIA. — In  planning  a  columbarium 
provision  should  be  made  for  the  requirements 
of  the  poor  as  well  as  for  those  who  are  in  a 
position  to  pay  large  fees ;  little  distinction, 
however,  should  be  made  between  the  two. 
Where  the  former  niches  are  enclosed  with 
plain  stone  or  marble  slabs,  the  latter  will  be 
finished  with  wrought  iron,  copper,  silver,  or 
gold  grills.  The  niches  or  receptacles  should 
be  formed  to  hold  from  one  to  five  urns  in  a 


FIG.  3.— Columbarium,  Oddfellows'  Cemetery, 
San  Francisco. 

single  compartment.  In  constructing  the 
niches,  the  materials  employed  should  be  such 
as  will  occupy  the  least  amount  of  space.  The 
urns  in  use  are  known  as  the  "  Box "  or 
"Vase  "  shape;  the  first-mentioned  measures 
16  in.  by  8  in.,  and  is  8  in.  high.  The  box  urn 
being  generally  used,  provision  is  made,  with 
few  exceptions,  for  this.  The  fronts  of  the 
niches  are  enclosed  with  marble  or  glass  slabs, 
or  grills  made  of  iron,  copper,  or  other 
material.  Many  beautiful  examples  of  the 
latter  are  to  be  seen  in  the  columbarium  at 
Golder's  Green,  London.  These  grills  are 
held  in  position  by  detachable  copper  or  iron 


fittings.  The  interior  of  the  niches  may  be 
plastered,  distempered,  or  otherwise  artisti- 
cally decorated.  When  the  grill  of  the  niche 
is  fitted  with  a  lock,  then  the  superintendent 
of  the  columbarium  is  supplied  with  a  dupli- 
cate key,  so  that  he  may  periodically  clean 
the  compartment,  and  if  required,  cover  the 
urn  with  flowers. 

SITE  OF  A  CREMATORIUM. — The  Cremation  Act 
of  Parliament  (2  Ed.  VII.,  c.  8.),  states  that 
no  crematorium  shall  be  constructed  nearer 
to  any  dwelling  than  200  yds.,  except  with  the 
consent,  in  writing,  of  the  owner,  lessee, 
and  occupier  of  such  house,  nor  within 
50  yds.  of  any  public  highway,  nor  in  the 
consecrated  part  of  any  burial-ground  of 
any  burial  authority.  No  crematorium 
shall  be  erected  until  the  plans  of  the  site 
thereof  have  been  approved  by  the  Local 
Government  Board,  and  no  human  remains 
shall  be  burned  therein  until  such  time  as 
the  burial  authority  has  certified  to  the 
Home  Secretary  that  the  crematorium  is 
completed  and  properly  equipped  for  the 
purpose  of  the  disposal  of  human  remains 
by  burning. 

COST  OF  CREMATORIA. — The  cost  of  the 
crematoria  in  England  has  varied  con- 
siderably ;  that  at  Woking  cost  £5,022  ; 
Leicester,  including  a  chapel  for  inhuma- 
tion services,  and  various  other  buildings, 
£13,880;  Birmingham,  £5,000;  Liver- 
pool, £8,000;  Ilford,  £7,000;  while  the 
municipal  crematorium  at  Hull  cost 
£2,700  only.  A.  C.  F. 

"  Cultivation  Tank  "  (Scott-Moncrieff).— 
In  lieu  of  an  ordinary  septic  tank,  Mr.  Scott- 
Moncrieff  has  used  what  may  be  described  as  a 
tank  full  of  flints,  with  the  object  of  providing 
anchorages  for  the  cultivation  of  colonies  of 
anaerobic  bacteria  throughout  the  mass  of  the 
sewage.  In  such  a  tank  the  sewage  enters  at 
the  bottom  and  filters  upwards  through  the 
stones  which  are  carried  on  a  grating,  and 
escapes  at  the  top  by  means  of  a  suitable 
overflow,  near  the  level  of  the  inlet.  This 
tank  effluent  is  then  distributed  over  the 


92 


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MUNICIPAL   AND   SANITAKY  ENGINEERING. 


DAM 


uppermost  of  a  series  of  nitrifying  trays  of 
boxes  with  perforated  bottoms,  and  filled  with 
coke  of  the  size  of  beans.  The  system  was 
first  tried  on  a  practical  scale  at  Ashtead 
(1891),  and  has  been  adopted  at  the  Caterham 
Barracks,  and  many  other  places  at  home  and 
abroad.  The  separation  of  the  anaerobic  from 
the  aerobic  organisms  is  well  provided  for  by 
this  method  of  treatment,  and  importance  is 
attached  to  this  feature  as  forming  the  desired 
liquefaction  of  the  sewage,  and  the  satisfactory 
nitrification  of  the  final  effluent.  For  large 
installations,  however,  the  question  of  cost 
would  appear  to  be  an  important  factor,  inas- 
much as  it  is  cheaper  to  provide  a  given 
capacity  in  a  clear  tank  than  in  the  interstices 
of  materials  such  as  flints  filled  into  the  tank 
space ;  also,  any  undigested  matter  is  more 
readily  removed  from  the  ordinary  open  tank 
than  from  a  cultivation  tank.  The  sewage 
would,  in  most  cases,  doubtless  require  screen- 
ing and  rough  sedimentation  before  passing 
into  the  cultivation  tank. 

Dale's  Muriate  of  Iron  Process  of 
Sewage  Purification. — This  process  em- 
ploys a  concentrated  solution  of  perchloride 
of  iron  for  the  disinfection  and  deodorisation 
of  sewage. 

Damp  Buildings,  prevention  of, — The 

first  thing  is  to  obtain  a  fairly  dry  site,  or  to 
drain  it  as  described  further  on,  under  the 
heading  of  sub- soil  drainage.  If  the  soil  is 
retentive  of  moisture,  the  walls  should  rest 
on  lias  lime  or  Portland  cement  concrete,  to 
retard  the  rising  of  moisture,  and  the  whole 
site  between  the  outer  walls  should  be  covered 
with  similar  material,  6  in.  thick,  the  compo- 
sition of  which  has  already  been  described. 
It  is  generally  considered  advisable  before 
laying  the  concrete  to  put  3  in.  or  4  in.  of  good 
brick  rubbish  over  the  surface  of  the  ground 
and  lightly  ram  it  so  as  to  leave  it  in  a  perma- 
nent porous  layer,  but  there  is  some  doubt  as 
to  its  actual  utility.  The  inner  cross  walls 
and  sleeper  walls  may  be  built  on  this  layer 
of  concrete. 


WALLS. — The  basement  or  semi-basement 
walls  may  be  protected  from  the  external  earth 
in  contact  with  them  by  a  layer  of  bitumen, 
or  asphalte,  or  even  by  tarring,  as  in  Fig.  1, 
or  by  making  a  cavity  wall  as  Fig.  2.  Where 
there  is  no  basement,  a  horizontal  damp- 
proof  course  is  inserted  6  in.  above  the  ground 
level  as  in  Fig.  3.  The  horizontal  damp-proof 
course  may  be  Callender's  pure  bitumen, 
Robinson's  roll  asphalte,  patent  asphalted 
sheet  lead,  a  double  course  of  slates  in  cement, 
or  horizontally  perforated  glazed  tiles.  Where 
the  walls  are  subject  to  spray,  or  a  very  moist 
atmosphere,  they  are  built  hollow,  a  4J  in. 
skin  being  placed  outside  the  ordinary  wall 
and  bonded  to  it  as  in  Fig.  4.  At  the  window 
and  door  openings,  bricks  must  be  bonded 
across  the  cavity  in  the  wall ;  and  over  the  top 
of  the  door  and  sash  frames,  sheet  lead  must  be 
built  in  and  carried  beyond  the  woodwork  on 
each  side  to  prevent  moisture  dropping  on  it. 
The  cavity  must  in  all  cases  be  ventilated  by 
air-bricks,  or  perforated  tiles,  as  shown  at  the 
bottom,  and  similar  openings  at  the  top  of  the 
wall.  The  brickwork  should  be  composed  of 
thoroughly  well-burnt  bricks  and  good  mortar. 
An  ordinary  building  brick  should  not  absorb 
more  than  one-sixth  of  its  weight  of  water 
when  left  in  for  24  hours,  and  a  foundation 
brick  of  best  quality  should  not  absorb  more 
than  6  %.  Other  means  of  preventing  damp 
from  passing  through  a  wall  are  covering 
it  with  hanging  tiles  or  slates,  coating  it 
with  Szerelmey  liquid  or  with  Fluate,  or 
painting  it.  At  the  top  of  a  wall  the  moisture 
is  prevented  from  travelling  downwards  by  an 
impervious  covering  of  stone  coping,  Portland 
cement  coping,  blue  brick  lumps,  or  brick-on- 
edge  in  cement,  having  underneath  it  a  layer  of 
slates  or  tile  creasing.  Projecting  copings, 
cornices,  window-sills,  &c.,  must  be  throated 
on  the  under-side  to  throw  off  the  drips  of 
water  clear  of  the  walls. 

ROOFS. — The  most  usual  coverings  for  roofs 
are  slates  and  tiles.  Slates  are  split  off  from 
a  naturally  formed  clay  rock  with  cleavage 
planes,  and,  when  of  good  quality,  absorb 
very  little  moisture.  Stood  in  a  pail  of  water 


93 


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ENCYCLOPEDIA  OF 


DAM 


over-night  to  half  their  depth,  the  water 
should  not  have  risen  1  in.  on  the  face  in  the 
morning.  Slates  are  of  various  sizes,  the 
most  general  being  Countesses  20  in.  by 
10  in.,  laid  with  a  lap  of  3  in.,  and  a  visible 
margin  or  gauge  of  8  in.  if  head  nailed,  and 

FIG.  1. 


10  in.  or  10^  in.  by  6  in.  by  £  in.,  are 
generally  used  for  house  roofs.  They  should 
be  slightly  curved  in  the  length  so  as  to  lie 
closely  at  the  ends,  and  be  laid  with  a  lap  of 
not  less  than  2|  in.  and  margin  of  3^  in.  to 
4  in.,  as  shown  in  Fig.  6.  The  pitch  of  a 

FIG.  3. 


FIG.  2. 


FIG.  4. 


FIG.  1.— External  Damp-Course.        FIG.  2.— Cavity  Wall. 
FIG.  3. — Horizontal  Damp-proof  Course.         FIG.  4. — Hollow  Wall. 


8J  in.  if  centre  nailed.  The  slates  are  laid 
to  break  joint,  and  the  lap  is  the  amount  the 
tail  of  a  slate  overlaps  the  head  of  those  in 
the  course  next-but-one  below,  as  in  Fig.  5. 
Corrugated  pantiles  are  only  used  on  common 
sheds  as  they  absorb  much  water  and  are 
very  heavy.  Hard  burnt  plain  tiles,  about 


slated  roof  may  be  from  25°  to  30°,  but  a 
tiled  roof  should  be  from  45°  to  60°,  as  owing 
to  the  less  lap  there  would  be  more  tendency 
for  moisture  to  get  in,  unless  the  pitch  were 
increased. 

PLUMBERS'  WORK. — The  plumbers'  work  of 
a   roof    is   of   the   utmost   importance.     The 


94 


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MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


DAM 


ridges  and  hips  should  be  covered  with,  say  layer  boards  on  each  side.  When  a  gable 
6  Ib.  lead  dressed  over  2  in.  rolls,  and  the  wall  stops  at  the  roof,  the  slates  or  tiles  should 
wings  secured  by  tingles.  The  valleys  should  overlap  the  verge  by  1J  in.,  and  have  a 


CC/ps  to 
o/otvn  flashing 
at  each  anq/Le 


FIG.  10. 


FIG.  7. 


FIG.  5. — Section  through  Slate  Covering  to  Roof.  FIG.  6. — Section  through 
Tiled  Eoof.  FIG.  7.— Stepped  Flashing  to  Chimney  Stack.  FIG.  8.— Plan 
of  Lead  Parapet  Gutter.  FIG.  9.— Section  through  Lead  Parapet  Gutter. 
FIG.  10. — Section  through  Drip  of  Lead  Gutter. 

have  5  Ib.  soakers  laid  with  laps  between  the  cement  fillet  underneath.  When  the  gable  is 
slates  on  each  roof  plane,  or  a  secret  gutter  carried  up  to  form  a  parapet  wall  above  the 
should  be  formed  with  5  Ib.  lead  over  the  roof  4  Ib.  lead  flashing  should  be  laid,  6  in. 

95 


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ENCYCLOPAEDIA   OF 


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on  the  slates  and  4  in.  up  the  wall,  with  an 
apron  cover  of  4  Ib.  lead  1^  in.  clear  of  the 
roof,  and  the  top  edge  stepped  into  the  courses 
of  the  brickwork.  Similar  flashing  should 
be  carried  round  chimney  stacks,  where  they 
penetrate  the  roof,  with  a  small  gutter  behind, 
as  Fig.  7.  The  eaves  of  a  roof  behind  a 
parapet  wall  are  finished  with  a  7  Ib.  lead 
gutter  on  gutter  boards  and  bearers,  with  a 
maximum  width  of  6  in.,  a  fall  of  1|  in.  in 
10  ft.,  a  drip  at  the  end  of  every  sheet,  and 
roll  at  the  highest  part,  when  the  gutter  falls 
both  ways.  The  plan  will  be  as  shown  in 
Fig.  8,  the  cross  section,  to  a  larger  scale,  as 
Fig.  9,  and  the  section  through  a  drip  as  in 
Fig.  10.  H.  A. 

Dams:  Earthen,  Masonry  and  Con- 
crete.— Earthen — Masonry —  Concrete  —  Ferro- 
Concrete. 

EARTHEN  DAMS  are  used  when  a  valley  is 
to  be  converted  into  a  natural  or  impounding 
reservoir.  The  valley  should  be  as  high  as 
possible  above  the  sea  level,  with  a  large 
gathering  ground,  and  with  a  narrow  neck 
between  the  hills,  where  the  embankment  to 
act  as  a  dam  could  be  placed.  The  subsoil 
should  be  an  impervious  rock  such  as  granite, 
not  chalk  or  limestone  which  is  subject  to 
fissures,  or  gravel  which  is  freely  pervious. 
In  the  latter  cases,  the  reservoir  would  have 
to  be  lined  with  puddled  clay.  Borings  or 
trial  pits  are  necessary  to  ascertain  the 
depth,  nature  and  configuration  of  the  subsoil 
and  adjacent  strata.  Any  surface  material 
that  can  be  excavated  to  deepen  the  valley 
may  be  used  to  help  in  the  formation  of  the 
dam.  The  essential  part  of  the  dam  is  a 
central  wall  of  clay  puddle,  punned  in  thin 
layers,  carried  down  sufficiently  into  the  strata 
below  to  prevent  any  leakage  underneath,  and 
extended  well  into  the  sides  of  the  valley 
with  the  same  object.  The  material  for  the 
embankment  must  be  selected  with  care,  and 
if  it  can  be  obtained  from  the  bottom  of  the 
reservoir,  this  method  has  the  advantage  of 
increasing  the  capacity  of  the  reservoir  and 
reducing  the  cost  of  transit  of  the  material. 


An  earthen  dam  is  usually  cheaper  than  one 
of  masonry  or  concrete,  but  it  occupies  a  very  . 
large  area  of  ground,  and  requires  a  very 
large  quantity  of  material.  It  must  be  not 
less  than  5  ft.,  and  often  8  ft.  to  10  ft.  above 
the  highest  water  level,  surmounted  by  a 
roadway  20  ft.  to  30  ft.  wide  in  all,  and  the 
side  slopes  will  depend  upon  the  material 
used;  generally  they  are  3  to  1  inside  and 
2  to  1  outside.  The  puddled  clay  wall  stops 
short,  say.  4  ft.  below  the  surface  to  prevent 
the  changes  of  atmospheric  conditions  affect- 
ing it,  and  particularly  to  prevent  it  from 
drying  and  cracking.  At  the  level  of  the  bed 
of  the  reservoir  the  puddle  should  be  about 
one-third  the  maximum  depth  of  water  in 
thickness,  tapering  off  to  say  half  of  this  at 
the  top  and  three-fourths  at  the  bottom. 
The  puddle  should  be  well  rammed  in  layers 
not  exceeding  2  ft.  thick,  and  in  dry  weather 
must  be  watered  to  secure  adhesion  between 
the  different  layers.  Next  to  the  puddle  wall 
must  be  placed  selected  material  retentive 
of  moisture,  and  on  the  outside  the  best 
remaining  material  deposited  in  layers  in- 
clining towards  the  central  wall.  The  outer 
slope  is  always  covered  with  grass,  either  sods 
or  seeds,  to  bind  the  material  and  prevent 
disintegration  by  the  weather,  and  drained 
to  prevent  slips.  If  the  top  is  not  required 
to  be  finished  as  an  ordinary  roadway  it  may 
be  turfed,  with  a  slight  fall  each  way  to  throw 
off  the  water.  The  inner  slope  may  be  turfed 
to  the  mean  water  level,  but  is  more  often 
covered  with  coarse  flint  ballast  or  stone 
pitching.  The  stone  pitching  varies  from 
rough  rubble  set  on  end  to  properly  squared 
sets,  the  chief  use  being  to  prevent  damage 
by  the  wash  of  waves  in  a  large  exposed 
reservoir.  The  same  slopes  are  kept  through- 
out the  dam,  but  the  depth  and  bottom  width 
decrease  as  the  ends  are  approached.  The 
outlet  from  a  reservoir  is  the  most  difficult 
part  to  arrange,  a  pipe  through  an  embank- 
ment is  extremely  liable  to  cause  failure  from 
water  creeping  along  its  outside  surface  and 
washing  away  some  of  the  material;  the  leak- 
age may  be  very  slight  at  first,  but  will  rapidly 


96 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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increase  if  neglected.  The  overflow  from  the 
reservoir  must  be  by  means  of  a  masonry  weir 
or  bye-wash.  The  accompanying  illustration, 
Fig.  1,  shows  a  section  through  an  earthen 
dam  of  the  Glasgow  Waterworks.  The  cost 
of  the  embankment  of  a  reservoir  may  be  from 


mediate  layer  of  bitumen,  as  in  Fig.  2,  and 
with  no  puddle  wall.  In  these  cases  the  great 
difficulty  is  to  prevent  cracks  in  the  con- 
tinuous surface  of  the  concrete  which  may  be 
due  to  imperfect  junctions  between  the  work 
of  different  days,  contraction  of  the  cement 


9'0" 
top  or  e/noanffmertt 

7b/o  Mfater  LeveL 


"orc/ngr    I 2" Chi 


Whir/stone 
D&Cum  i/ne   2OOfC.   above 


•Same/ ,  yravet    ar/Tof  bouiders 


Oroffcrnce    datum 


FIG.  1. — Section  through  Earthen  Dam. 


6d.  to  Is.  per  cube  yard.  The  approximate 
cost  of  the  whole  reservoir,  including  every 
expense  of  earthwork,  paddling,  pitching, 
waste- weirs,  valves,  &c.,  but  exclusive  of  land 
will  be  given  in  £  per  million  gallons  by 
25,000 


the  formula 


where  m  =  contents  in 


25  +  m' 

millions    of    gallons.      Under    unfavourable 
circumstances  it  may  be  10%  to  25%  more, 


in  setting,  different  qualities  of  cement  used 
on  the  same  job,  or  slips  or  subsidences  in 
the  earth  backing  due  either  to  insufficient 
consolidation,  too  steep  an  angle,  or  improper 
filling. 

MASONRY  DAMS. — An  earthen  dam  resists 
the  pressure  of  water  by  mere  mass  without 
any  scientific  disposition  of  the  material  being 
possible,  but  it  is  so  extravagant  of  space  that 


CariLena/er's    pure 


EMBANKMENT 
"to  €"  concrete     under    sheeting 


FIG.  2. — Keservoir  Lined  with  Waterproofed  Concrete. 


but  favourable  circumstances  may  reduce  the 
cost  to  from  25%  to  50%  less.  Sometimes 
the  inner  face  of  the  dam  is  protected  from 
the  percolation  of  water  by  a  bed  of  puddled 
clay  under  the  protective  covering,  and  in 
smaller  reservoirs  the  banks  are  lined  with 
concrete  alone,  or  concrete  with  an  inter- 
M.S.E. 


numerous  cases  arise  where  a  solid  structure 
must  be  built  that  shall  have  the  minimum 
bulk.  A  masonry  wall  of  parallel  thickness 
is  not  suitable  where  the  material  must  be 
economised.  Under  the  thrust  due  to  the 
pressure  of  the  water  the  wall  acts  as  a 
cantilever,  the  stress  increasing  from  top  to 
97  H 


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ENCYCLOPEDIA   OF 


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bottom,  the  resistance  must  therefore  be 
increased  by  adding  to  the  thickness  towards 
the  base.  In  French  practice  a  masonry 
wall  with  plain  straight  batter  is  considered 
sufficient,  the  top  width  three-tenths  of  the 
height,  the  inner  face  vertical  and  the  outer 
face  with  such  batter  that  the  width  of  the 
base  is  seven-tenths  of  the  height.  In 
English  and  American  practice  the  distribu- 
tion of  material  is  more  nearly  proportioned 


Water    ievei 


\*      -  20'.  O*- 


these  points  will  be  the  curve  of  stability 
when  the  reservoir  is  empty.  When  the 
reservoir  is  full  the  method  will  be  as  follows: 
taking  the  part  down  to  line  A  the  pressures 
due  to  the  head  of  water  will  be  in  the  form 
of  a  triangle  with  a  base  at  A  of  62'5  X  20 
=  1,250  Ibs.  The  total  pressure  will  then  be 

-  =  12,500  Ibs.  acting  at  right  angles 

2> 

to  back  of  wall  through  the  centre  of  gravity 
of  the  triangle.  This  pressure  must 
be  combined  with  the  weight  of  the 
part  considered,  and  where  the  re- 
sultant cuts  line  A  will  be  one  point 
in  the  curve.  The  part  from  A  to 
B  must  next  be  considered,  and  the 
pressures  due  to  the  head  of  water 
will  now  vary  from  1,250  Ibs.  at  A  to 
62-5  X  40  =  2,500  Ibs.  at  B.  The 
total  pressure  acting  through  the 
centre  of  gravity  of  the  quadrilateral 
1,250  +  2,500 


will    be 


X     20     = 


}*----  62'.6'  ----- 

FIG.  3. — Principles  of  designing  Modern  Dam. 

to  the  stress,  allowing  for  the  weight  of  the 
superincumbent  parts  as  well  as  for  the 
increasing  thrust  of  the  water  as  a  greater 
depth  is  reached.  The  principle  of  designing 
and  calculating  the  main  stresses  of  a  modern 
masonry  dam  is  exemplified  in  Fig.  3,  which 
shows  a  conventional  section  of  a  dam  70  ft. 
high.  The  curve  of  stability  when  the 
reservoir  is  empty  will  be  found  by  first 
dividing  the  section  into  any  convenient 
number  of  parts  as  shown  by  the  dotted  lines 
A,B,  C,  and  D.  Find  the  centre  of  gravity  of 
each  part,  and  through  each  centre  of  gravity 
drop  a  vertical  line  to  cut  the  assumed  base 
line  of  each  part.  The  curve  drawn  through 


37,500  Ibs.,  and  this  amount  must 
be  combined  with  the  resultant  from 
the  first  portion.  The  resultant  thus 
formed  is  then  combined  with  the 
weight  of  wall  from  A  to  B,  and 
another  point  in  the  curve  will  be 
given  where  the  resultant  of  the  last 
step  cuts  line  B.  In  a  similar  manner 
the  other  divisions  of  the  wall  may  be 
worked  out  and  other  points  found, 
through  which  the  curve  of  stability  when 
reservoir  is  full  may  be  drawn.  Other 
information  may  be  given  upon  the  same 
diagram,  such  as  the  maximum  com- 
pression produced  in  the  masonry  at  each 
level  where  the  position  of  the  curve  has 
been  found.  Fig.  4  shows  a  cross  section 
through  the  Vyrnwy  dam  with  the  principal 
figures  of  the  stresses,  and  a  pressure 
diagram  below  it  showing  the  distribu- 
tion of  the  load  upon  the  foundations. 
This  masonry  dam  with  a  flood  water  head 
against  it  of  129  ft.  is  a  magnificent  piece 
of  engineering  with  considerable  claim  to 
architectural  merit.  Besides  the  main  stresses 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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referred  to  above  two  others  have  received 
considerable  attention  in  recent  years,  viz., 
the  shear  stresses  and  the  upward  pressures 
due  to  penetration  of  water  below  the  masonry. 
The  most  important  contribution  to  the  subject 
of  shear  in  masonry  dams  was  given  by  Prof. 
Unwin  in  a  series  of  articles  in  Engineering 


T 


dam  about  34  ft.  high  in  the  Hudson  Water- 
works, New  York.  This  dam  was  built  in 
alternate  50-ft.  sections  at  one  time,  with  a 
tongue-and-groove  tar  joint  between  the  sec- 
tions. After  the  first  lift  of  the  forms  had 
been  filled,  a  3-ft.  layer  of  concrete  was  placed 
in  one  section  on  one  day,  then  permitted  to 


FIG.  5. 


FIG.  4. — Section  of  Vyrnwy  Dam.        FIG.  5. — Section  of  Spillway  of  Dam. 


for  April  21,  May  12,  and  June  30,  1905, 
and  the  upward  pressures  have  been  discussed 
somewhat  fully  by  correspondents  in  The 
Engineering  Record  during  June  and  July, 
1908.  In  consideration  of  the  enormous 
stake  in  life  and  property  connected  with  the 
design  of  dams,  these  matters  are  of  very 
serious  import,  but  they  are  rather  beyond 
the  scope  of  the  present  work. 

CONCKETE    DAMS. — Fig.    5    shows    a    cross 
section  through   the  spillway   of  a   concrete 


set  a  day  while  a  3-ft.  layer  was  placed  in  an 
alternate  section,  after  which  another  3-ft. 
layer  was  placed  in  the  first  section,  and  so 
on.  The  surface  of  each  layer  was  thoroughly 
brushed  and  cleaned,  then  wetted  and  covered 
with  a  thin  coat  of  1  :  2  Portland  cement 
mortar  before  the  next  layer  was  placed.  The 
concrete  used  in  the  dam  was  mixed  quite  wet 
in  the  proportion  of  1  part  of  Hudson  Port- 
land cement,  2'8  parts  sand,  and  5£  parts 
broken  stone,  these  proportions  having  been 
99  H  2 


DAM 


ENCYCLOPEDIA   OF 


DES 


found  to  give  a  slight  excess  of  fine  material. 
The  sand  was  found  to  contain  from  6  to  8  °/0 
of  loam.  Thorough  tests  were  made  to 
discover,  if  possible,  the  effect  of  the  presence 
of  the  loam,  and,  as  good  results  were  obtained 
in  the  tests,  the  sand  was  used.  In  the  early 
part  of  the  work  the  broken  stone  was  screened, 
but  the  greater  part  of  the  concrete  was  made 
with  crusher-run  broken  stone,  in  which  the 
largest  pieces  did  not  exceed  2^  in.  in  their 
greatest  dimension. 

FEREO  -  CONCRETE  DAMS.  —  The  Ambursen 
Hydraulic  Construction  Co.  of  Boston,  Mass., 
give  a  remarkable  section  of  a  reinforced 


FIG.  6. — Section  of  Ferro-Concrete  Dam  in 
Pleasure  Park. 

concrete  dam  erected  by  them  in  a  pleasure 
park,  shown  in  Fig.  6.  The  principal 
promenade  leads  right  through  the  dam,  in  at 
one  end  and  out  at  the  other ;  the  interior  of 
the  dam  is  treated  as  a  grotto,  being  decorated 
with  rock-work,  moss,  ferns,  &c. ;  the  stiffen- 
ing division  walls  are  perforated  by  arches, 
seats  are  placed  in  each  bay,  and  the  whole  is 
lighted  by  electricity.  The  main  point  about 
such  work  is  that  it  must  be  not  only  strong, 
but  must  be  waterproof;  to  obtain  this  the 
mixture  must  be  rich  in  cement,  not  leaner 
than  1:2:4,  with  fine  aggregate  and  plenty 
of  water.  Lime  has  been  added  to  the  cement 
used  in  mixing  concrete  for  reservoir  walls 
with  the  view  of  preventing  the  percolation  of 


moisture  and  rendering  the  wall  waterproof. 
There  is  some  evidence  that  it  is  efficient,  but 
until  more  is  known  about  the  action  of  free 
lime  in  cement  it  would  be  wiser  to  adopt 
more  usual  means,  such  as  using  a  richer 
mixture  of  cement  towards  the  face,  or  pro- 
tecting it  with  one  of  the  bituminous  com- 
pounds, externally  or  a  little  way  in  from  the 
face.  H.  A. 

Deacon's  Meter. — (See "  WATER  SUPPLY.") 

Deep  Well  Water. — (See  "  UNDERGROUND 
WATER,"  "WELLS,"  and  "WATER  SUPPLY.") 

Deodorants,  or  substances  which  re- 
move smells,  must  be  carefully  dis- 
tinguished from  true  disinfectants,  many 
of  which,  however,  are  also  deodorant. 
To  get  rid  of  a  bad  odour  or  to  mask  it 
by  a  stronger  one  does  not  necessarily 
indicate  that  disease-producing  organisms 
are  at  the  same  time  affected,  and  mere 
deodorants  are  often  an  evil  by  causing 
a  false  sense  of  security.  Charcoal  and 
dry  earth  absorb  most  odours,  but  have 
little  or  no  action  on  bacteria.  On  the 
other  hand  many  perfumes  and  aromatic 
bodies  not  only  mask  bad  smells  but 
also  cause  oxidation  and  are  inimical  to 
bacteria,  and  therefore  may  act  as  real 
disinfectants,  but  not  in  proportion  to 
their  odour.  In  chlorine  and  oxone  the 
two  powers  are  strongly  developed.  (See 
"DISINFECTANTS.") 

Destructors.  —  General :  the  "  Destructor 
System  "  of  dealing  with  Refuse — The  Variable 
Composition  of  Refuse — Quantity  of  Refuse- 
Different  Types  of  Destructors — Accessory  Plant 
— Dust-Catcher,  Boilers,  Economisers — Thermal 
Storage — Remarks  on  the  Design  of  Destructor 
Plants — Recent  Improvements  in  Destructors — 
Production  of  Steam  Power — Money  Value  of 
Refuse  Fuel  at  Combined  Destructor  and 
Electric  Stations  —  Total  Costs  of  Burn- 
ing Refuse,  including  Capital  Charges. —  The 
term  "destructor"  is  applied  to  a  high 


100 


DES 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


DES 


temperature  furnace  specially  designed  for  the 
disposal  of  town  refuse  by  burning.  The 
system  was  introduced  about  the  year  1870, 
and  has  since  been  subjected  to  great  modi- 
fication and  improvement.  It  may  be  said 
that  during  the  past  40  years  the  destructor 
system  has  had  its  birth,  has  grown  into 
maturity,  and  has  latterly  been  pursued  to 
an  extent  which  has  enabled  the  practice  to 
be  reduced  to  certain  well-understood  general 
principles.  Many  years  of  practical  experience 
has  led  to  the  design  of  efficient  types  of 
destructors,  has  shown  what  is  the  true 
calorific  value  of  average  town  refuse,  so  that 
manufacturers  are  now  able  to  give  definite 
and  reliable  guarantees  of  performance  such 
as  both  users  and  makers  may  with  a  reason- 
able degree  of  certainty  expect  to  realise. 
The  mere  disposal  of  the  refuse  is  not,  as  a 
rule,  the  only  consideration  kept  in  view  in  a 
modern  refuse  destructor  station.  A  com- 
plete installation  for  a  population  of,  say, 
50,000  persons  may  cost  from  ,£5,000  to 
£6,000  to  erect,  according  to  local  circum- 
stances, and,  in  addition  to  the  destructor  cells 
proper,  usually  includes  machinery  and  plant 
for  the  removal  and  disposal  of  the  residual 
clinker,  for  its  crushing  and  manufacture  into 
paving  slabs,  bricks,  mortar,  or  other  saleable 
products,  also  steam  and  engine  power  for 
actuating  the  various  plant  required  at  such 
a  station.  It  will,  therefore,  be  evident 
that  the  working  expenses,  maintenance,  and 
depreciation  of  a  fully  equipped  installation 
must  necessarily  be  considerable,  and  that 
with  the  view  of  reducing  this  annual  expense 
to  a  minimum  it  becomes  necessary  to  turn 
to  account  any  and  every  by-product  or  resi- 
dual material  which  can  be  really  diverted  to 
profitable  use. 

THE  VARIABLE  COMPOSITION  OF  TOWN  REFUSE. 
—The  material  dealt  with  in  destructors  is 
of  variable  composition.  It  not  only  varies 
widely  in  different  localities,  but  the  summer 
and  winter  supplies  of  refuse  in  any  town  is 
rarely  of  the  same  calorific  value.  A  destructor 
installation  must  therefore  be  adapted  to  cope 
with  this  unavoidable  fluctuation  where  a 


fairly  steady  and  uniform  demand  for  the 
surplus  heat  available  for  motive  power  pur- 
poses exists.  The  constituents  commonly  met 
with  in  the  refuse  include,  ashes  and  cinders, 
small  pieces  of  coal,  dust,  waste  paper  and 
cardboard  boxes  and  packings,  straw,  shavings, 
rags,  vegetable  and  animal  matter,  scullery 
and  kitchen  wastes,  bottles  and  preserved 
food  tins,  broken  crockery,  glass,  bones,  &c. 
The  amount  of  cinders,  ashes,  and  coal  is  not 
large,  and  has  a  tendency  to  decrease  of  recent 
years,  owing  to  the  extended  use  of  gas  fires, 
and  the  consumption  of  ready-made  artificially 
preserved  tinned  and  bottled  foods.  Contrary 
to  what  may  be  expected,  the  house  refuse  of 
the  poorer  districts  of  a  town  very  usually 
contains  the  largest  proportion  of  cinders  and 
coal,  which  obviously  formed  the  most  valuable 
parts  of  the  refuse  from  a  calorific  standpoint. 
This  is  probably  due  to  the  greater  extrava- 
gance or  want  of  care  of  the  poorer  classes  in 
the  sifting  out  of  cinders  from  their  household 
refuse,  and  its  retention  for  further  use,  and 
also  to  the  fact  that  the  refuse  from  these 
quarters  is  more  strictly  household  refuse 
with  a  much  smaller  admixture  of  garden  and 
vegetable  waste.  As  may  be  anticipated,  the 
refuse  of  the  coal  mining  districts  of  the 
northern  and  Midland  towns  possesses  greater 
calorific  value  than  that  of  the  southern  and 
eastern  counties,  but  the  distinction  is  not 
always  so  marked  as  might  be  supposed  hav- 
ing regard  to  the  relative  prices  of  coal  in 
different  quarters. 

The  quantity  of  refuse  to  be  dealt  with  from 
a  given  population  is  a  matter  requiring 
investigation  when  designing  a  destructor 
installation.  In  London  this  amounts  to  from 
4  to  5  cwt.  per  head  per  annum,  or  to  from 
200  to  250  tons  per  1,000  of  the  population 
per  annum.  In  the  neighbourhood  of  the 
Metropolis  varying  amounts  have  been 
reported,  viz  :  2J  cwt.  per  head  per  annum  at 
Leyton,  3^  cwt.  at  Hornsey,  and  as  much  as 
7  cwt.  at  Baling.  In  the  north  of  England 
the  total  collected,  exclusive  of  street  sweep- 
ings, has  been  put  at  8  cwt.  per  head  per 
annum.  On  the  average  from  5  to  10  cwt. 


DES 


ENCYCLOPEDIA  OF 


DES 


per  head  per  annum  must  be  allowed  for. 
The  weight  of  refuse  is  also  variable,  and 
great  discrepancy  will  usually  arise  in 
estimates  based  upon  so  many  "  loads "  col- 
lected per  annum.  The  "  load  "  may  range 
from  10  cwt.  to  1  ton,  though  from  12  to  14 
cwt.  is  commonly  about  the  weight  of  an 
ordinary  good  one-horse  load  of  average 
house  refuse  weighed  in  fine  weather.  Much 


employed  be  of  the  most  perfect  type  for  the 
primary  purpose  of  burning  the  refuse,  without 
thereby  giving  rise  to  nuisance  or  incon- 
venience to  the  neighbouring  public.  The 
secondary  object  of  the  plant  must  be  to  take 
the  fullest  possible  advantage  of  the  heat 
given  out  by  burning  the  refuse  for  the 
generation  of  steam.  In  that  way  the  cost  of 
collecting  and  disposing  of  the  material  may 


PIG.  1. — Section  of  Fryer's  Destructor. 


depends  on  whether  the  refuse  is  wet  or 
dry,  and  whether  it  is  collected  from  shop 
properties,  or  residential  quarters.  Shop 
refuse  is  usually  of  a  light  character  and 
consists  largely  of  paper,  shavings,  boxes 
and  packings,  and  is  of  but  little  calorific 
value. 

A  population  of,  say,  50,000  persons  will 
produce  domestic  household  refuse  at  the  rate 
of  about  40  tons  per  day.  As  it  is  essential 
that  this  material  should  be  satisfactorily  and 
economically  disposed  of  day  by  day,  it  is  of 
first  importance  that  the  furnaces  and  plant 


be  reduced.  Some  general  idea  of  what  may 
be  regained  in  this  connection  may  be  gathered 
from  the  following  calculation : — Forty  tons 
of  refuse  per  day,  or  about  12,500  tons  per 
annum,  giving  an  evaporative  efficiency  at  the 
rate  of  1  Ib.  of  water  per  pound  of  refuse  (a  result 
readily  obtained  in  practice),  will  develop 
a  steam-power  of  1,400,000  I.H.P.  hours 
annually,  calculating  upon  a  steam  con- 
sumption for  condensing  engines  of  20  Ibs. 
of  steam  per  I.H.P.  per  hour.  Then,  allowing 
3  Ibs.  of  coal  as  the  fuel  consumption  per 
I.H.P.  hour,  this  gives  an  equivalent  of  about 


102 


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MUNICIPAL   AND   SANITAEY   ENGINEEEING. 


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1,880  tons  of  coal  per  annum,  showing  the 
refuse  in  this  case  to  be  from  one-seventh 
to  one-sixth  the  value  of  coal  for  steam-raising 
purposes. 

DIFFERENT  TYPES  OF  DESTRUCTORS. — Since 
Mr.  Fryer  erected  his  destructor  in  Man- 
chester, in  1876,  many  different  designs  of 
furnace  have  been  introduced,  as  experience 
has  directed  attention  to  numerous  important 
points  where  improvements  could  be  intro- 
duced. The  principal  furnaces  to  which 
attention  should  be  directed  are  those  of 
"Fryer,"  "Warner,"  "Horsfall,"  "  Meldrum," 
"Beaman  &Deas,"  the"Heenan" 
twin-cell,  and  the  "  Sterling" 
destructor. 

FRYER'S  DESTRUCTOR  (Fig.  1), 
as  already  mentioned,  is  one  of 
the  earliest  types,  and  for  a  long 
time  formed  the  basis  of  several 
subsequent  designs.  It  consists 
of  a  block  of  cells  or  furnaces, 
usually  arranged  "back  to  back" 
in  pairs.  Each  cell  measures  in- 
ternally about  9  ft.  by  5  ft.,  and 
is  covered  by  a  fire-brick  arch 
3  ft.  6  in.  in  height  above  the 
grate  area.  The  furnace  floor 
slopes  at  an  inclination  of  about 
1  in  3,  and  the  area  of  the  fire 
grate  is  25  sq.  ft.  This  destructor 
ordinarily  deals  with  from  4  to 
6  tons  of  refuse  per  cell  per  24 
hours,  and  is  known  as  a  low 
temperature  destructor.  The  outlets  for  the 
products  of  combustion  are  at  the  back  of  the 
cells  near  the  refuse  feed-opening,  which  is  an 
undesirable  arrangement. 

WARNER'S  DESTRUCTOR  (Fig.  2)  is  similar 
to  Fryer's  in  general  arrangement,  but  differs 
therefrom  in  many  points  of  detail.  It  pro- 
vides special  charging  hoppers,  dampers  in 
the  Hue,  dust-catching  arrangements,  rocking 
fire-bars,  and  a  modified  position  of  the 
outlets  for  the  escape  of  the  products  of 
combustion.  The  cells  are  5  ft.  wide  by  11  ft. 
deep,  the  rearmost  portion  consisting  of  a 
fire-brick  drying  hearth.  The  grate  area  is 


25  sq.  ft.,  and  the  amount  of  refuse  consumed 
varies  from  5  to  8  tons  per  cell  per  24  hours. 
HORSFALL'S  DESTRUCTOR  (Figs.  3,  4,  5)  has 
been  on  the  market  for  a  great  many  years,  and 
is  well  known  both  in  this  country  and  on  the 
Continent  of  Europe.  It  was  probably  the 
earliest  type  to  work  at  really  high  tempera- 
tures, and  many  improvements  have  been 
made  in  its  design  where  experience  has 
shown  them  to  be  necessary.  It,  will  be  seen 
from  the  illustration  that  the  general  arrange- 
ment of  the  Fryer  type  has  been  followed  in 
the  Horsfall  design  ;  but  that  there  are  many 


FIG.  2. — Warner's  Destructor  and  Boiler. 

important  modifications,  such,  for  example, 
as  those  of  the  arrangement  of  flues  and  flue 
outlets  for  the  products  of  combustion  and 
the  introduction  of  a  blast  duct  through 
which  air  is  conducted  to  the  closed  ashpit. 
The  feed  holes  are  placed  at  the  back  of  the 
furnace,  whilst  the  flue  openings  for  the 
removal  of  gases  are  situated  at  the  front  of 
the  cell,  so  that  the  gases  from  the  drying 
refuse  pass  on  their  way  to  the  main  flue  over 
the  hottest  parts  of  the  fire  and  through  a  red- 
hot  reverberatory  arch.  The  steam  jet,  a 
feature  in  the  Horsfall  furnace,  forces  air  into 
the  closed  ashpit  at  a  water-gauge  pressure  of 


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about  f  in.  to  1  in.,  thus  producing  a  tempera- 
ture of  from  1,500°  to  2,000°  F.  The  blast 
air  is  conveyed  on  its  way  to  the  grate  through 
cast-iron  boxes  at  the  sides  of  the  furnaces, 
as  shown  in  the  figure,  the  boxes  also  having 
the  further  object  of  preventing  the  clinker 
adhering  to  the  sides  of  the  cells,  the  removal 
from  which  causes  damage  to  the  brickwork 
by  the  clinkering  tools.  The  Horsfall  furnace 
deals  with  from  8  to  10  tons  per  cell  per 
24  hours.  Considerable  improvements  and 
additions  in  accessory  details  have  been  made 


removing  the  fine  ash.  and  two  Meldrum 
steam  jet  "  blowers "  are  provided  to  each 
furnace  capable  of  supplying  any  pressure  of 
blast  up  to  6  in.  water  column.  The  pressure 
usually  used  does  not  exceed  1^  ins.  The 
furnaces  are  arranged  for  hand  feeding  from 
the  front,  but  hopper  feeding  of  the  customary 
type  can  be  adapted  if  preferred.  The  flue 
gases  pass  away  to  the  boilers  and  from 
thence  are  further  utilised  in  an  air-heater 
or  continuous  regenerator  consisting  of  cast- 
iron  pipes  from  which  the  air  is  delivered 


FIG.  3. — Section  of  HorsfalPs  Destructor. 


in  connection  with  this  type  of  furnace  during     through  the  Meldrum  "  blowers  "  at  a  tem- 


recent  years. 

MELDRUM'S  DESTRUCTOR  (Fig.  6)  differs  in 
general  arrangement  from  the  types  already 
referred  to.  It  is  a  modern  high-temperature 
destructor,  now  widely  adopted,  and  capable 
of  giving  good  steam-raising  results.  This 
destructor  is  practically  one  long  cell,  fed  and 
clinkered  at  four  or  five  different  furnace 
mouths,  according  to  the  number  of  grates 
installed,  and  by  this  means  an  approximately 
uniform  temperature  is  maintained  through- 
out. The  ashpits  are  each  closed  air-tight 
by  a  cast-iron  plate  and  air-tight  doors  for 


perature  of  about  300°  F.,  thus  assisting  to 
keep  up  the  temperature  of  the  furnace  and 
facilitate  combustion.  High-pressure  Lanca- 
shire boilers  of  large  capacity  are  usually 
provided  for  the  accumulation,  during  periods 
of  light  demand,  of  a  reserve  of  steam.' 
Storage  is  obtained  by  using  the  difference 
between  the  maximum  and  minimum  working 
steam  pressure  and  the  permissible  fluctua- 
tion of  water-levels  in  the  boiler.  From  50  to 
60  Ibs.  of  refuse  per  square  foot  of  grate  area 
per  hour  are  consumed  by  the  Meldrum 
furnaces,  as  compared  \vith  about  22  Ibs.  per 


104 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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square  foot  in  the  low  temperature  destructors. 
Installations  of  the  Meldrum  type  have  been 
largely  adopted  where  a  special  feature  of  the 
destructor  station  has  been  to  produce  the 


FIG.  4.— Section  of  4-Cell  Tub  Fed  Plant  by  Horsfall 
Destructor  Co.,  Ltd. 


utmost  steam  power  possible  for  purposes 
of  sewage  or  water  pumping,  or  for  electric 
light  or  power  generation. 

BEAMAN  &  DEA'S  DESTRUCTOR  is  another 
high-temperature  furnace,  the  patents  of 
which  are  now  in  the  hands  of  Messrs. 
Meldrum  Bros.,  of  Manchester.  The  special 
features  are  the  flat  grate  area  of  25  sq.  ft., 
and  the  sloping  drying  and  feeding  hearth 
immediately  below  the  feed  hopper  on  the 
tipping  platform.  At  the  back  of  the  cells  is 
a  high  temperature  combustion  chamber, 
placed  between  the  cell  proper  and  the  main 
flue.  A  secondary  air  supply  also  meets  the 
fumes  as  they  pass  over  the  fire-bridge.  The 
destructor  is  fitted  with  a  powerful  air  blast, 
and  is  generally  installed  in  conjunction  with 
Babcock  &  Wilcox  water-tube  boilers.  This 
destructor  will  consume  about  20  tons  of 
refuse  per  cell  per  24  hours,  and  is  a  good 
steam  generator. 

"  HEENAN  "  TWIN-CELL  DESTRUCTOR  (Figs.  7, 
8,  and  9)  is  one  of  the  most  recent  destructors, 
and  is  built  by  Messrs.  Heenan  &  Froude,  of 
Manchester.  The  standard  arrangement  of 


this  destructor,  with  Lancashire  boiler  and 
regenerative  apparatus,  is  shown  in  the  plan 
(Fig.  7).  In  the  section  (Fig.  8)  a  water- 
tube  boiler  and  hot-air  duct  leading  to  the 
regenerator  is  shown.  A  plant  of  this 
type  is  in  use  at  Gloucester,  consisting 
of  two  "twin-cells."  A  "twin-cell" 
comprises  two  furnace-grates,  each  of 
39  sq.  ft.  in  area,  with  a  fire-bridge 
between.  Each  pair  of  cells  are 
capable  of  cremating  25  tons  of  refuse 
in  24  hours,  and  are  worked  together. 
A  maximum  amount  of  clinker  of  25  % 
of  the  refuse  is  guaranteed.  The 
furnaces  work  at  a  temperature  of  over 
2,000°  F. :  that  of  the  flues  before  the 
boilers  is  from  1,400°  to  1,800°,  and 
after  the  boilers  from  400°  to  700°. 
One  Babcock  &  Wilcox  boiler  is  pro- 
vided to  each  pair  of  cells,  and  the 
weight  of  water  evaporated  from  and 
at  212°  F.  per  pound  of  refuse  burned 
is  from  T25  Ibs.  to  2  Ibs.  Forced 
draught  is  produced  by  an  electric  fan  of 
12  B.H.P.,  running  at  950  revolutions 
per  minute.  About  125  H.P.  is  obtained 
from  the  refuse  when  burning  150  tons 
weekly.  The  cells  are  fed  through  an  iron 


FIG.  5.— Section  of  4-Cell  Tub  Fed  Plant  by  Horsfall 
Destructor  Co.,  Ltd. 

shoot  at  the  back,  and  the  clinkering  is  done 
from  the  front  of  the  furnace.  The  cost  of 
the  destructor  was  about  £4,150. 


105 


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ENCYCLOPEDIA  OF 


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THE  "  STERLING  "  DESTRUCTOR  has  of  recent 
years  been  installed  at  Hackney,  Bermondsey, 
Gravesend,  Heston  and  Isleworth,  and  other 
places.  The  destructor  and  electricity  works 
inaugurated  at  Hackney  in  1901  are  amongst 
the  largest  combined  destructor  and  electric 
stations  yet  put  down.  The  estimated  cost  of 
the  destructor  alone  was  £22,000  for  dealing 
with  about  38,000  tons  of  refuse  yearly.  The 
plant  consists  of  twelve  cells  arranged  in  three 
groups,  each  group  having  a  central  supple- 
mentary combustion  and  dust-depositing 


careful  attention,  both  from  a  sanitary  as  well 
as  an  economical  point  of  view.  The  whole 
of  each  day's  refuse  is  burned  within  the 
24  hours.  The  electric  energy  consumed  by 
the  elevators  and  distributors  is  about  "35  of 
a  kilowatt-hour  per  ton  of  refuse  elevated,  and 
the  amount  of  the  lift  is  43  ft.  from  ground 
level  to  the  storage  bins.  The  forced  draught 
is  obtained  from  three  centrifugal  fans  driven 
by  15  H.P.  "  Rhodes  "  motors.  The  guaranteed 
capacity  of  the  destructor  is  1  60  tons  of  refuse 
per  day  of  24  hours.  The  "Sterling" 


FIG.  6. — Meldrum's  Destructor. 


chamber,  three  Babcock  &  Wilcox  water-tube 
boilers,  fired  by  heat  from  the  destructors, 
and  built  for  a  working  pressure  of  250  Ibs. 
per  square  inch ;  three  fans,  each  driven  by 
an  electric  motor,  for  providing  the  necessary 
forced  draught ;  three  elevators,  also  driven 
by  electric  motors,  for  raising  the  refuse  and 
delivering  it  into  high-level  refuse  storage 
bins,  whence  it  is  drawn  down  as  required 
into  the  cells ;  a  large  Green's  economiser ; 
and  a  complete  range  of  flues  and  by-passes 
which  permit  the  gases  to  be  taken  through 
the  boilers  and  economiser,  through  the 
boilers  alone,  through  the  economiser  alone, 
or  direct  to  the  chimney  shaft  without  passing 
through  either  boilers  or  economiser.  The 
best  means  of  handling  the  refuse  has  received 


destructor  may  be  generally  described  as  a 
compound  furnace,  having  at  least  two  cells, 
each  with  a  drying  hearth,  a  grate,  and  a 
closed  air-tight  ashpit,  combined  with  a 
special  chamber  placed  between  the  cells. 
This  chamber  serves  the  purpose  of  a  supple- 
mentary combustion  and  dust-depositing  cell, 
and  is  made  large  enough  for  the  reception  of 
infected  mattresses,  bedding,  and  even  of 
an  entire  ox.  Calculating  upon  the  basis 
of  1  Ib.  of  steam  per  pound  of  refuse  fed 
into  the  cells,  the  "  Sterling "  furnace 
(two  cells),  burning  2,800  Ibs.  of  refuse  per 
hour,  will  give  140  I.H.P.  continuously 
per  pair  of  cells  at  20  Ibs.  steam  per 
I.H.P.  Steam-blast  is  not  recommended 
by  the  makers,  and  the  furnaces  of  this  type 


106 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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are  assisted  by  forced  draught   produced  by 
a  fan. 

ACCESSORY  PLANT  AT  DESTRUCTOR  INSTAL- 
LATIONS.— Much  auxiliary  plant  is  now  in  use 
for  the  complete  equipment  of  a  modern 
destructor  station.  Such  accessories  are 
mainly  designed  to  ensure  the  following 
points  : — (1)  The  complete  combustion  of  the 
refuse  and  gases  given  off ;  (2)  The  avoidance 
of  all  possibility  of  nuisance  in  carrying  on 
the  working  of  the  destructor  ;  (3)  the  reduc- 
tion of  working  expenses  by  labour-saving 
devices,  and  the  introduction  of  means  of 
utilising  the  residuals 
produced  on  the  works, 
including  the  profitable 
employment  of  the  sur- 
plus heat;  (4)  and  the 
reduction  of  wear  and 
tear  and  maintenance  ex- 
penses generally.  The 
utilisation  of  clinker  from 
destructors  has  given 
scope  for  a  variety  of 
plant,  such  as  mortar 
mills,  crushers,  slab- 
making  machinery,  for 
example,  as  that  of 
Messrs.  C.  &  A.  Musker, 
Ltd.,  of  Liverpool,  and 
artificial  stone  -  plant  as 
made  by  Messrs.  Field- 
ing &  Platt.  Messrs.  Musker  have  also 
introduced  a  brick-making  plant,  as  now  used 
by  Bradford  and  Liverpool  Corporations. 
The  approximate  cost  of  a  6,000-brick  plant 
is  £1,900,  and  of  a  10,000-brick  plant 
£2,300.  The  cost  of  production  of  the  bricks 
averages  from  12s.  to  14s.  per  1,000.  For  the 
purpose  of  manufacture  of  clinker  into  bricks, 
slabs,  &c.,  the  material  as  it  leaves  the 
furnaces  must  first  be  crushed  to  suitable 
sizes.  A  suitable  machine  for  this  purpose  is 
the  Cox  &  McTaggart  clinker-crushing  plant, 
consisting  essentially  of  a  pair  of  grooved 
rollers  with  removable  faces  made  of  specially 
hard  metal  and  chilled,  driven  by  heavy  and 
powerful  gearing. 


At  Kensington  a  plant  costing  about  £6,000 
has  been  installed  for  making  road-paving 
blocks.  The  treated  clinker,  after  crushing, 
is  mixed  with  15  %  of  Trinidad  asphalte  and  a 
certain  proportion  of  fine  dust,  and  then 
pressed  under  two  tons  to  the  square  inch  into 
paving  blocks  8  in.  by  3  in.  by  3  in.  and 
4  in.  deep,  for  use  upon  secondary  roads. 

At  Liverpool,  trials  have  been  carried  out 
in  the  construction  of  labourers'  dwellings  of 
crushed  clinker  steel  armoured  concrete  for 
walls,  roofs,  and  floors.  After  mixture  with 
cement  the  materials  are  filled  into  moulds  to 


PIG.  7. — Heenan's  Destructor. 

form  large  slabs  representing  a  complete  side, 
floor  or  roof  of  a  room. 

At  Fulham  a  plant  was  put  down  by 
Messrs.  Fielding  &  Platt  at  a  cost  of  £2,365 
for  the  manufacture  of  bricks  and  flags  in  con- 
nection with  a  12-cell  "  Horsfall "  destructor 
completed  in  the  year  1900.  The  materials 
manufactured  have  been  sold  to  the  various 
departments  at  the  following  prices  : — bricks 
35s.  per  1,000 ;  paving  flags  4s.  per  square 
yard;  mortar  10s.  6d.  per  cubic  yard,  at  the 
works. 

Artificial  slabs,  concrete  bricks,  mortar, 
&c.,  are  also  made  on  a  large  scale  at  the 
Bradford  Corporation  Works,  where  nearly 
60,000  tons  of  refuse  are  dealt  with  annually 


107 


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ENCYCLOPEDIA   OF 


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by   the  destructors,  at  a  cost    for  labour    of 
about  ll|rf.  per  ton. 

An  improved  system  for  the  easier  removal 


the    objectionable    quenching     of     the     hot 
material  within  the  building  is  avoided. 

The  use  of  forced  draught  is  an  important 


HEENAN     REFUSE    DESTRUCTOR 
5    CELL.    PLANT 

FIG.  8. — Heenan's  Destructor. 


of  clinker  from  the  furnaces  has  been  adopted 
at  Blackpool,  Bradford,  Hanley,  Fulham, 
and  several  other  places.  The  arrangement 
consists  of  an  overhead  railway  with  clinker 


and  essential  detail  in  all  destructor  stations. 
In  the  "Meldrum"  system  the  air  is  delivered 
into  a  closed  ashpit  by  means  of  a  steam  jet 
blower  of  special  construction,  used  in  con- 


CROSS     SECTION     THROUGH     CELI 

FIG.  9. — Heenan's  Destructor. 

buckets  suspended  upon  a  rail  leading  direct  junction  with  special  made  fire  bars  spaced 
from  each  furnace  to  the  cooling  space  or  only  -fa  in.  apart,  and  thus  enables  steam  to 
crushing  machine.  The  handling  of  the  be  economically  raised  with  materials  contain- 
clinker  is  thus  reduced  to  a  minimum,  and  ing  only  a  small  percentage  of  combustibles. 

108 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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The  proportion  of  steam  used  in  the  forced 
blast  is  about  15%  of  the  total  raised. 
At  the  set  of  six  new  cells  built  at  West 
Hartlepool  in  1903  was  installed  a  system  of 
forced  draught  on  the  Horsfall  new  "  hot- 
blast  system,"  in  which  each  side  air  box  in 
every  cell  contains  its  own  separate  steam 
blower,  so  that  no  condensation  of  the  steam 
in  the  passages  is  possible.  The  air  tem- 
perature in  the  ashpits  is  increased  to  over 
400°  F.,  which  materially  quickens  com- 
bustion. A  special  form  of  superheater  has 
also  been  adopted  for  heating  the  steam  to 


of  the  site,  some  form  of  top-feed  closed 
hopper  system  is,  on  the  whole,  preferable, 
provided  the  mechanical  devices  adopted 
are  quite  simple  in  construction  and  work 
smoothly  in  daily  use.  The  fires,  however, 
should  not  be  too  suddenly  fed  with  large 
charges  of  green  refuse,  otherwise  the  diffi- 
culty of  maintaining  a  steady  steam  pressure 
will  be  increased,  and  some  risk  of  imperfect 
combustion  of  gases  incurred.  With  hand- 
feed  at  the  furnace  mouth  the  cost  of  an 
inclined  roadway  and  raised  tipping  platform 
is  dispensed  with,  and  there  is  also  an  advan- 


FIG.  10. — Ley  ton  Destructor.     Section  throiigh  Cell  and  Boiler. 


the  jets,  increasing  the  efficiency  of  the 
blast  and  reducing  the  quantity  of  steam 
consumed. 

Improvements  have  been  made  of  late  years 
in  the  feeding  arrangements  to  destructor 
cells  in  order  to  avoid  the  handling  or  storage 
of  the  refuse,  to  avoid  nuisance,  and  to  save 
cost  of  labour.  Of  these  arrangements  may 
be  cited  the  apparatus  of  Boulnois  and  Brodie, 
the  "  feeding  hoppers  "  of  the  Horsfall  Destruc- 
tor Co.,  and  the  special  feeding  arrangement 
adopted  by  Messrs.  Meldrum  Bros,  for  dealing 
with  fish  and  slaughter-house  offal.  Unless 
there  is  some  special  local  reason  for  adopting 
a  hand-fed  arrangement,  such  as  the  exigencies 


tage,  when  combined  with  the  continuous 
grate  and  divided  ashpit  arrangement,  that 
the  feeding  in  of  small  quantities  of  refuse 
does  not  very  materially  affect  the  tempera- 
ture of  the  cell,  as  in  the  case  of  a  large 
charge  such  as  a  ton  or  a  load. 

The  "  dust  catcher "  is  an  important 
feature  in  installations  of  the  Horsfall  type, 
and  has  for  its  object  the  prevention  of  the 
escape  of  fine  dust  from  the  chimney  shaft 
into  the  atmosphere.  It  consists  of  an  outer 
annular  chamber  and  an  inner  well.  The 
flue  gases  enter  the  outer  chamber  and  swirl 
rapidly  round  it,  thereby  throwing  off  the 
suspended  dust  against  the  outer  wall. 


109 


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ENCYCLOPAEDIA  OF 


DES 


Clearing  doors  are  provided  for  periodically 
removing  the  dust  thus  deposited  within  the 
chambers. 

Other  accessory  details  connected  with 
destructor  plants  include  counterbalanced  fur- 
nace fronts,  back-feeding  or  charging  doors, 
water-sealed  feed-opening  doors,  dampers,  and 
furnace  lining  blocks. 

The  principal  accessories  for  heat  utilisa- 
tion include  various  forms  and  settings  of 
boilers,  regenerators,  economisers,  and  super- 
heaters. 

BOILEES. — The  boilers  mostly  used  are  of 
the  Lancashire  and  the  water-tube  type. 
The  Lancashire  boiler,  where  there  is  a  fairly 
uniform  demand  for  steam,  is  a  reliable  steam 
raiser,  and  for  steady  work  has  much  to 
recommend  it.  The  thermal  capacity  is 
large,  and  a  steady  steam  pressure  can  be 
maintained.  Water-tube  boilers,  are,  how- 
ever, largely  used  in  connection  with  destruc- 
tors, as  the  steam  power  is  very  generally 
applied  to  the  generation  of  electricity,  in 
which  connection  the  water-tube  boiler  is 
well  adapted  for  coping  with  the  sudden 
demands  for  steam  often  required  in  the 
generation  of  energy  for  lighting  and  motive 
power.  Water-tube  boilers  have  a  small 
water  capacity,  a  relatively  large  heating 
surface,  and  are,  therefore,  quick  steaming 
boilers,  but  their  small  thermal  capacity 
tends  to  unsteady  steam  production,  and  this 
class  of  boiler  is  liable  to  smoke  with  bitu- 
minous coal,  so  that  smokeless  fuel  must  be 
used.  The  use  of  pure  water  is  also  neces- 
sary to  avoid  incrustation  in  the  tubes.  The 
Babcock  &  Wilcox  water-tube  boiler  has  been 
largely  used  in  connection  with  destructor 
stations,  and  has  been  found  well  suited  to 
the  work.  The  Stirling  boiler  is  also  em- 
ployed in  a  similar  connection. 

ECONOMISEKS,  EEGENERATORS,  &c.  —  To 
secure  the  full  value  of  available  heat  in  the 
flue  gases,  in  addition  to  using  boilers  of 
large  heating  surface  as  compared  with  their 
water  capacity,  it  is  necessary  to  provide 
"  economisers  "  and  "  regenerators  "  through 
which  the  gases  pass  on  their  way  to  the 


chimney  shaft.  This  cooling  of  the  gases 
must  not,  however,  be  carried  too  far,  other- 
wise the  chimney  draught  will  be  impaired. 
A  temperature  of  some  350°  to  450°  F.  on 
entering  the  chimney  may  be  regarded  as 
satisfactory. 

"  Economisers "  are  placed  in  the  main 
flue  leading  to  the  chimney  shaft,  and  the  hot 
flue  gases  thus  utilised  to  heat  the  feed-water 
to  the  boilers.  Green's  and  Hudson's  econo- 
misers are  much  used  for  this  purpose.  The 
Green  economiser  is  a  flue-heated  feed-water 
heater,  by  means  of  which  the  hot  gases  may 
be  reduced  in  temperature  from  650°  F.  to 
350°  F.,  and  the  feed-water  heated  some 
150°  to  250°  F. 

In  the  Meldrum  system  as  installed  at 
Sheerness,  a  Sugden  superheater  is  placed  in 
the  down-take  immediately  behind  the  boiler, 
and  arranged  to  give  about  125°  F.  of 
superheat  to  the  steam.  Beyond  the  super- 
heater is  provided  a  Meldrum's  "  regenerator," 
or  continuous  air-heater,  so  that  in  addition 
to  actual  steam-raising  the  hot  gases  are 
further  utilised  for  superheating  the  steam, 
and  then  for  heating  the  air  supply  for 
combustion  up  to  a  temperature  of  about 
350°  F. 

THERMAL  STORAGE. — The  object  sought  in 
the  storing  of  heat  energy  is  to  accumulate 
surplus  heat  during  hours  of  light  load,  as,  for 
example  in  electric  central  station  work,  so  as 
to  utilise  this  stored  energy  through  the  hours 
of  towering  peak  load.  The  thermal  storage 
installation  originally  put  in  at  the  Shoreditch 
combined  destructor  and  electric  light  station 
was  subsequently  altered  to  store  the  hot 
feed-water  instead  of  storing  the  actual  steam, 
as  was  originally  intended,  and  in  this  modified 
form  has  done  good  service.  In  1904  an 
installation  of  thermal  storage  was  put  down 
by  the  Kensington  and  Knightsbridge  and  the 
Netting  Hill  Electric  Light  Companies  for  the 
purpose  of  increasing  the  capacity  of  their 
plant  at  their  joint  station  at  the  Wood  Lane 
Works.  Large  hot  water-feed  cylinders  were 
placed  over  the  steam  drums  of  the  existing 
water-tube  boilers  and  immediately  below  the 


110 


DES 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


DES 


water  storage  tanks.  The  main  idea  of  the 
system  is  to  increase  the  rating  of  the  boilers 
at  the  hours  of  peak  load  by  feeding  the 
boiler  with  water  at  boiler  temperature  during 
those  hours,  this  water  having  been  previously 
heated  to  the  desired  temperature  by  live 
steam  during  the  hours  preceding  the  peak. 

REMAKES  ON  THE  DESIGN  OF  DESTRUCTOR 
PLANTS. — The  proper  design  and  capabilities 
of  the  refuse  destructor  and  its  accessory 
plants  have  not  been  well  understood  until 
within  comparatively  recent  years.  The 
utilisation  of  refuse  as  fuel  is  an  essentially 
practical  subject  and  one  in  which  every 
"  improvement "  must  be  submitted  to  a 
prolonged  practical  test  before  it  can  be 
pronounced  as  good.  The  best  results  of 
to-day  are  obtained  through  a  knowledge  of 
the  failures  and  defects  of  the  past.  Like 
most  mechanical  apparatus  and  inventions, 
that  destructor  plant  is  best  which  is  simple, 
strong,  and  easily  worked,  if  combined,  of 
course,  with  efficiency.  It  would  be  unwise 
to  lay  down  any  hard  and  fast  rule  as  to  a 
particular  type  of  plant  as  being  absolutely 
the  best  for  all  cases  and  localities.  Due 
regard  must  be  had  to  the  conditions  of  the 
case  and  local  requirements.  The  choice  of 
plant  and  the  general  design  of  a  station 
requires  to  be  entrusted  to  an  engineer 
experienced  in  such  matters  in  order  to  ensure 
the  best  results.  The  following  general  obser- 
vations, however,  will  be  a  guide : — 

The  temperature  in  the  cells  must  be 
sufficiently  high  to  reduce  the  refuse  to  an 
entirely  innocuous  clinker,  and  all  vapours 
given  off  should  pass  through  an  adjoining 
red-hot  cell,  or  through  a  chamber  whose 
heat  is  maintained  by  the  ordinary  working 
of  the  furnaces  themselves  to  a  temperature 
of  from  1,500°  to  2,500°  F.,  so  as  to  pre- 
vent the  escape  of  noxious  gases. 

To  maintain  a  uniformly  high  temperature, 
the  destructor  requires  to  be  so  worked  that 
whilst  one  set  of  cells  is  recharging,  another 
set  is  at  a  full  red  heat. 

The  furnaces  and  plant  require  to  be  strong, 
simple,  and  easily  worked  without  stoppages, 


111 


and  should  contain  no  mechanical  complica- 
tions. The  installation  should  withstand 
variations  of  temperature  and  readily  admit 
of  being  repaired.  The  plant  must  admit  of 
being  understood  and  worked  by  stokers  of 
average  intelligence,  so  that  its  continuous 
working  may  be  ensured,  and  that  the  cost  of 
working  may  be  kept  as  low  as  possible. 

Clinkering  and  recharging  requires  to  be 
done  as  speedily  as  possible  to  prevent  the 
inrush  of  cold  air,  which  would  reduce  the 
temperature  of  the  main  flues  and  the  calorific 
efficiency  of  the  refuse.  Where  boilers  are 
provided  for  stoking  with  both  refuse  and 
coal,  a  system  of  dampers  should  be  arranged 
so  that  when  coal  fuel  is  in  use  only  the 
refuse  cells  may  be  shut  off  from  the  boilers ; 
otherwise  the  cold  air  passing  through  the 
cells  and  into  the  coal  furnaces  will  materially 
reduce  the  calorific  efficiency  of  the  coal. 

The  chimney  draught  must  always  be 
assisted  by  forced  draught  from  fans  or 
steam  jet  to  the  extent  of  from  1-5  in.  to  2  in. 
of  wafcer-gauge  pressure  in  the  ashpit. 

In  districts  where  the  question  of  nuisance 
from  the  chimney  shaft  is  of  importance, 
boilers  must  not  be  placed  immediately  over 
a  furnace  in  such  a  way  as  to  present  a  large 
cooling  surface  to  the  gases,  for  then  their 
temperature  would  be  reduced  before  they 
have  been  rendered  wholly  innocuous. 

If  steam  power  is  an  important  part  of  the 
system,  ample  boiler  capacity  and  hot-water 
storage  feed  tanks  should  be  provided ;  also 
the  flue  gases  may  be  utilised  in  heating  the 
air  supply  to  the  grates  and  the  feed  water  to 
the  boilers.  For  a  high  fuel  efficiency  a  large 
proportion  of  C02  should  be  sought  in  the 
cells,  with  as  little  excess  of  air  or  free  oxygen 
as  possible. 

Considering  the  somewhat  trying  nature  of 
the  work,  a  destructor  station  should  be 
worked  in  three  eight-hour  shifts  where  the 
plant  is  running  continuously.  A  bath-room 
in  connection  with  the  works  will  be  found 
not  only  a  boon  by  the  workmen,  but  a 
hygienic  necessity. 

In  order  to  derive  the   full   advantage  of 


DES 


ENCYCLOPAEDIA   OF 


DES 


good  points  of  design,  it  is  necessary  that  the 
furnaces  and  plant  be  carefully  and  intelli- 
gently worked,  and  the  efforts  of  the  firemen 
should  be  towards  obtaining  a  good,  hard 
vitreous  clinker,  and  perfect  cremation  of  the 
whole  of  the  refuse  without  the  escape  of 
unconsumed  vapours  of  any  kind ;  also  the 
inrush  of  cold  air  into  the  cells  and  flues 
must  be  avoided  as  much  as  possible,  other- 
wise the  calorific  results  obtained  will  be  low. 
The  great  improvements  which  have  taken 
place  in  the  design  and  management  of 
destructor  plants  have  contributed  materially 
to  the  carrying  on  of  such  works  in  the  midst 
of  populated  districts  with  a  minimum  of 
inconvenience  to  the  neighbouring  inhabitants. 

The  introduction  of  a  good  forced  draught 
and  high  temperature  furnaces  has  enabled 
larger  quantities  of  material  to  be  dealt  with, 
and  with  less  risk  of  allowing  unconsumed 
vapours  to  escape  into  the  atmosphere. 

THE  COST  OF  BURNING  EEFUSE  differs  widely, 
according  to  local  circumstances ;  at  Battersea 
the  cost  is  as  much  as  2s.  lOd.  per  ton,  whilst 
at  Bradford  it  is  burned  for  about  6d.  per  ton. 
Under  ordinary  circumstances  a  cost  of  Is. 
per  ton  for  labour,  supervision  and  small 
repairs  is  a  fair  average  figure.  The  amount 
of  refuse  burned  per  cell  per  hour  materially 
affects  the  cost  of  burning.  For  purposes  of 
comparison  the  best  way  of  stating  the  duty 
of  different  types  of  furnaces  is  to  state  the 
performance  of  the  furnace  in  pounds  per 
square  foot  of  grate  area  per  hour,  as  the 
furnaces  have  varying  grate  areas,  and  to 
give  the  consumption  in  tons  per  cell  is  some- 
times apt  to  mislead.  The  ordinary  low  tem- 
perature destructor,  working  without  forced 
draught,  deals  with  about  20  Ibs.  of  refuse 
per  square  foot  of  grate  area  per  hour,  and 
this  gives,  for  a  grate  area  of  25  sq.  ft.  each 
furnace,  a  duty  of  between  5  and  6  tons  per 
cell  per  day  of  24  hours.  This  consumption 
is  low,  and  with  forced  draught  may  be  greatly 
increased.  The  Beaman  &  Dea's  furnace  at 
Canterbury  has  been  found  to  deal  with  as 
much  as  77'5  Ibs.  per  sq.  ft.  of  grate  area 
per  hour,  and  the  same  type  cell  at  Llandudno 


deals  with  71'7  Ibs.  per  sq.  ft.  per  hour. 
The  consumption  in  the  Meldrum  furnaces  at 
Rochdale  is  66  Ibs.  per  square  foot  per  hour. 
The  amount  passed  through  the  furnaces 
depends  largely,  however,  on  the  mode  of  stok- 
ing, upon  the  degree  to  which  the  material  is 
thoroughly  cremated,  and  the  frequency  of 
the  removal  of  clinker.  The  amount  of 
residue  clinker  produced  is  usually  between 
25  %  and  33  %  of  the  material  dealt  with. 
Its  ultimate  disposal  is  a  question  of  consider- 
able importance  in  built-up  districts,  where 
the  ordinary  outlets  for  the  material  are  not 
available,  as  the  cost  of  cartage  or  barging 
to  the  suburbs  of  the  town  is  almost  pro- 
hibitive in  many  districts,  as  is  the  case  in 
Shoreditch,  where  the  total  residue  amounts 
to  32-8  %. 

RECENT  IMPROVEMENTS.  —  Some  of  the 
principal  improvements  made  in  destructor 
installations  during  recent  years,  include : — 

1.  The  use  of  high  temperatures  within  the 
cells  and  combustion  chambers  and  the  reduc- 
tion of  cold  air-leakage  into  the  furnaces. 

2.  Increased    durability    of    the    furnaces 
under  high  temperatures,  and  the  avoidance 
of  defects  caused  by  contraction  and  expansion 
owing  to  frequent  variations  of  temperature. 

3.  The  employment  of  hot-blast  and  forced 
draught,  and  the  reduction  of  power  used  in 
its  working. 

4.  The  extraction  of  the  full  calorific  value 
from    the  refuse,  and   the    interception   and 
utilisation  by  means  of  boilers,  economisers, 
or   feed-water   heaters,    superheaters,    regen- 
erators, hot-blast   draught,    &c.,    of  all  heat 
given  off  by  its  combustion,  and  its   fullest 
possible   application   to   the   performance    of 
profit-yielding  work. 

5.  Improvements  in  the  uniform  mainten- 
ance  of   steady  steam  pressures  and  in  the 
generation  of  high-pressure  steam. 

6.  The  practical  application  of    "thermal 
storage  "  in  the  employment  of  hot  water-feed 
cylinders,  thus  affording  a  certain  elasticity  of 
output  of  power. 

7.  Improvements  in    the   handling  of   the 
raw  refuse,  in  the  stoking  and  charging  of  the 


112 


DES 


MUNICIPAL   AND     SANITAEY  ENGINEERING. 


DES 


furnaces,  and  in  the  removal  and  disposal  of 
clinker,  line  ash,  &c. 

8.  The  reduction  of  working  and  mainten- 
ance costs  by  the  employment  of  the  various 
improvements  mentioned ;  also,  some  reduc- 
tion of  initial  capital  for  a  given  capacity  of 
plant. 

9.  The  employment  of  all  possible  means  of 
full    utilisation    of  residuals    created   at   the 
works  and  of  any  marketable  material  occur- 
ring in  the  refuse. 

10.  Various      sanitary     improvements     in 
connection  with  the  handling  and  storage  of 
the   refuse,    and   the   prevention   of   dust   or 
smells  from  the  chimney  shaft  and  destruc- 
tor station  generally. 

PRODUCTION  OF  STEAM-POWER.  —  Various 
recent  destructor  installations,  where  the 
production  of  steam-power  is  an  important 
consideration,  show  that,  on  the  whole,  an 
evaporation  of  from  1  Ib.  to  2  Ibs.  of  water 
per  pound  of  refuse  represents  the  full  avail- 
able calorific  value  of  town  refuse  for  power 
production,  and  it  is  not  usual  that  this 
average  can  be  maintained  over  long  periods 
of  working  under  ordinary  conditions.  A  few 
of  the  comparatively  recent  power-using 
installations,  taken  at  random,  are — (1)  the 
"  Horsfall  "  system  at  West  Hartlepool  Elec- 
tricity Works,  Fulham  Electricity  Works, 
Accrington  Electricity  Works,  and  Beckenham 
Electricity  Works;  (2)  "Meldrum's"  system  at 
Cleckheaton,  Burnley,  Darwen,  Port  Glasgow, 
Wandsworth,  and  Plumstead  ;  (3),  the  "  Hee- 
nan  "  system  at  Blackburn,  Gloucester,  and 
Wakefield;  (4),  the  "Sterling"  destructor 
system  at  Bermondsey  and  Hackney.  The 
amount  of  power  obtained  per  ton  of  refuse 
varies  with  the  character  of  the  material 
collected  in  the  particular  district  concerned. 
Taking  the  average  of  the  mean  results  of  six 
towns  in  the  vicinity  of  coal-producing  areas 
in  the  North  of  England  an  evaporation  of 
1'6  Ibs.  of  water  per  pound  of  refuse  is  shown, 
as  against  1'32  Ibs.  average  evaporation  of  six 
destructors  in  the  South-east.  The  difference 
is,  however,  often  much  more  marked,  as  the 
refuse  in  some  towns  is  of  an  unusually  rich 


character.  At  Warrington  the  Beaman  & 
Deas  furnaces  are  reported,  after  prolonged 
test,  as  generating  3  Ibs.  of  steam  per  pound  of 
refuse  throughout  the  year,  owing  to  the 
refuse  containing  some  60  %  to  70  %  of  cinders. 
At  King's  Norton  the  average  refuse  has  been 
analysed  and  found  to  contain  36'8  %  of 
carbon,  7'3  %  of  oxygen,  and  12'12  %  moisture, 
and  yielded  4,500  British  thermal  units  of 
heat  per  pound,  or  nearly  one-third  the  value 
of  average  Welsh  coal.  Ordinarily,  average 
town  refuse  is  found  to  contain  from  1,500  to 
3,000  British  thermal  units  per  pound,  and  to 
possess  a  calorific  value  of  from  one-tenth  to 
one-fifth  that  of  average  good  coal.  At  Llan- 
dudno,  the  refuse  is  of  very  low  calorific 
value,  especially  during  summer,  and  here 
the  Beaman  &  Deas  furnaces  (as  used  at 
Warrington  above  mentioned)  give  an  evapora- 
tion of  only  about  '7  Ib.  of  water  per  pound  of 
refuse.  A  low  value  was  also  obtained  at 
Royton  (Lancashire)  where,  upon  careful 
calorimeter  test,  only  997  British  thermal 
units  were  obtained  per  pound  of  refuse. 

MONEY  VALUE  OF  REFUSE  FUEL  AT  COMBINED 
DESTRUCTOR  AND  ELECTRIC  STATIONS.  —  For 
many  years  past  there  has  been  a  growing 
confidence  in  the  utility  of  modern  destructors 
as  power  producers  in  addition  to  being  mere 
destroyers  of  refuse  as  evidenced  by  recent 
combined  installations  at  such  districts  as 
Liverpool,  Nottingham,  Wolverhampton, 
Preston,  Hackney,  Bermondsey,  Fulham, 
Plumstead,  Woolwich,  and  others.  From 
recent  results  of  several  London  combined 
destructor  and  electric  stations  it  appears  that 
the  money  value  of  the  refuse  fuel  per  unit  of 
electric  current  generated  varies  from  about 
'Id.  to  "9d.  per  unit,  and  that  under  ordinary 
working  conditions  from  20  to  40  units  per 
ton  of  refuse  are  at  present  obtainable,  but 
that  over  limited  periods  much  higher  outputs 
have  been  generated.  However,  in  the  investi- 
gation of  the  value  of  destructors  to  electric  or 
other  power  stations  one  of  the  main  difficulties 
is  that  of  procuring  trustworthy  statistics  on 
a  uniform  basis  such  as  can  be  usefully 
compared  one  with  another. 


M.S.E. 


113 


DET 


ENCYCLOPAEDIA   OF 


DIS 


TOTAL  COSTS  OF  BURNING  REFUSE,  INCLUDING 
CAPITAL  CHARGES. — The  quantity,  or  rate,  at 
which  refuse  is  burned  by  a  modern  destructor 
commonly  lies  between  50  Ibs.  to  60  Ibs.  per 
square  foot  of  furnace  grate  area,  and  the 
cost  of  dealing  with  the  refuse  on  this  system 
varies  on  the  average  as  follows: — 

Per  ton  of  refuse, 
s.     d.  s.     d. 

Labour  of  burning  and  handling, 
including  stokers,  feeders,  yard- 
men, &c 0  8  to  1  10 

Supervision,  repairs,  removal  of 
clinker,  stores,  water,  rates  and 
taxes 0  6  to  0  9 

Capital  charges  (interest  and  redemp- 
tion)   0  6  to  1  9 


Per  ton  of  refuse  burned 


to     4     4 


ADVISABILITY  OF  COMBINING  DESTRUCTOR  AND 
ELECTRIC    OR    OTHER     POWER-USING    UNDER- 
TAKINGS.— There  has  been  much  difference  of 
opinion  in  many  quarters  as  to  the  advisability 
of  installing  refuse  destructors  in  conjunction 
with  power-using  stations  of  various  kinds ; 
but  generally  speaking,  it  may  be  stated  that, 
where  there  is  refuse  which  must  be  disposed 
of  and  works  to  which  some  form  of  motive 
power  must  be  supplied,  experience  has  shown 
that   the   modern   refuse  destructor   is   of   a 
certain    real   commercial   value   as   a   power 
producer,  and  that,  where  suitable  conditions 
exist,  the  outlay  involved  in  its  application  to 
that   duty   is   fully   justified   by   the   results 
obtainable,  not  forgetting  at  the  same  time, 
its    useful    sanitary    function    as    a    means 
of    refuse    disposal.      .(See    also    articles    on 
"  REFUSE   DISPOSAL,"   and    "  REFUSE  COLLEC- 
TION.") W.  H.  M. 

Detritus  Tank.—  (See  "SEWAGE  DISPOSAL.") 

Disconnecting  Trap. — A  trap  fixed  upon 
the  outlet  end  of  a  house  drain  to  break  aerial 
communication  between  the  drain  and  the 
public  sewer,  or  other  sewage  outlet.  Discon- 
necting traps  are  best  fixed  in  manholes,  in 
order  that  they  may  be  readily  reached.  In 
the  alternative  a  shaft  reaching  to  the  surface 
of  the  ground  may  be  provided.  It  is  desirable 


also  that  a  sweeping  eye  be  available  on  the 

outlet  end  of  the  trap,  to  afford  access  to  the 

drain    between    the 

trap  and  the    sewer, 

&c.       The     standing 

level  of  the  water  in 

disconnecting      traps 

should    be     at    least 

3  in.  below  the  inlet 

drain,  in   order   that 

a    cascade    may     be 

formed     by     sewage 

•    j      •.       mi  •  Disconnecting  Trap, 

passing  into  it.    This 

will  have  a  tendency  to  break  up  accumula- 
tions in  the  trap,  and  greatly  assist  in  keeping 
it  clean. 

Disinfectants. — Disinfection    in  the  mo- 
dern sense  may  be  regarded  as  having  had 
its  origin  in  the  year  1862,  when  Pasteur,  in 
response  to  an  offer  of  the  Academy  of  Science 
of  Paris  of  a  prize  for  "  an  attempt  by  means 
of  suitable  experiments  to  throw  new  light  on 
the    question    of    spontaneous    generation," 
demonstrated  the  possibility  of  sterilising  any 
substance  whatsoever.     Previous  to  the  work 
of  Pasteur  in  France  and  Koch  in  Germany 
little  had  been  done  in  investigating  the  life 
cycles  of  bacteria  with  a  view  to  ascertaining 
their  relation  to  disease.     Koch's  method  of 
isolating   pure   cultures   of    micro-organisms 
published  in  1881,  and  his  discovery  of  the 
tubercle  bacillus  in  the  following   year,  in- 
augurated a  new  era  in  preventive  medicine, 
and  for  the  first  time  in  the  history  of  that 
subject  made  the  study  of  disinfection  rational. 
In  the  light  of  the  knowledge  furnished  by 
this  and  later  bacteriological  work  the  mode 
of  action  of  disinfectants  became  plain ;  heat, 
whether    dry   or   moist,    destroyed    infective 
bacteria;    the    problem  of   the  resistance   of 
spores    was    solved ;    and    a  significant    dis- 
tinction was  drawn  between  antiseptics  which 
inhibit  the  growth  of    microbes  without  de- 
stroying  them   and   disinfectants  which   kill 
them  outright.     It  was  also  found  that  deodo- 
rants for  the  most  part  which  merely  mask  or 
absorb   odorous   gases   and   vapours    possess 


114 


DIS 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


DIS 


neither  the  properties  of  disinfectants  nor  of 
antiseptics. 

In  order  to  successfully  carry  out  the  work 
of  disinfection  it  is  clear  that  the  life  history, 
source,  environment,  and  specific  properties 
of  the  infective  agent  must  be  fully  known, 
as  also  the  nature  and  mode  of  interaction, 
chemical  or  physical,  which  obtains  between 
it  and  the  disinfectant. 

The  germicidal  efficiency  of  a  chemical 
disinfectant  is  often  determined  as  much  by 
physical  conditions  as  by  chemical  structure  ; 
and  to-day  an  efficient  disinfectant,  in  addition 
to  such  germicidal  efficiency,  must  be  capable 
of  penetrating  various  forms  of  organic  matter 
containing  bacteria,  must  be  free  from  corro- 
sive action  on  the  skin  and  on  metals,  must 
be  innocuous  to  man  and  the  higher  animals, 
must  be  homogeneous  in  all  conditions  of 
dilution  or  emulsion,  and  must  largely  retain 
its  germicidal  properties  in  the  presence  of 
organic  matter. 

Chemical  disinfectants  in  the  liquid  state 
are  obviously  much  more  effective  than  in  the 
gaseous  or  solid  condition.  The  efficiency  of 
a  disinfectant  liquid  depends  to  a  degree  on 
the  concentration  of  its  active  principle,  and 
also  on  the  particular  form  in  which  the  active 
principle  occurs.  In  the  present  state  of 
knowledge  it  is  impossible  to  state  exactly 
how  the  micro-organism  is  killed.  In  certain 
instances  it  is  probable  that  death  occurs 
through  coagulation  of  the  protein  of  the  cell, 
in  others  through  its  disruption.  In  solutions 
the  degree  of  ionisation,  and  in  emulsions  the 
viscosity  and  size  of  the  particles,  influence 
the  rate  and  completeness  of  penetration  of 
the  cell,  and  thus  of  the  germicidal  efficiency. 
The  temperature  of  the  disinfectant,  within 
certain  limits,  influences  directly  the  efficiency. 
Attempts  have  been  made  to  reduce  rate  and 
efficiency  of  disinfection  to  mathematical  form, 
but  until  very  much  more  is  known  of  the 
chemical  and  physical  factors  involved  in  this 
complex  problem  such  work  must  remain 
unsatisfactory. 

In  the  case  of  simple  and  stable  acids 
efficiency  is  approximately  proportional  to  the 


115 


degree  of  acidity.  In  alkalies  the  nature  of 
the  metal  forming  the  base  and  not  the 
degree  of  alkalinity  appears  to  govern  germi- 
cidal efficiency.  The  efficiency  of  certain 
organic  acids  has  been  found  to  be  inversely 
proportional  to  the  molecular  weight. 

Sulphurous  acid  obtained  from  burning 
sulphur  in  a  moist  atmosphere,  or  from  the 
liquefied  gas,  produces  a  slow  disinfection  of  a 
very  uncertain  character,  even  in  laboratory 
experiments.  Although  a  committee  of  Ger- 
man experts  unanimously  condemned  this 
disinfectant  nearly  a  quarter  of  a  century  ago, 
certain  British  sanitarians  still  employ  it,  for 
what  reason  one  cannot  conceive  other  than 
that  of  the  ancient  witch  doctor,  that  the 
more  abominable  the  potion  the  more  certain 
the  cure. 

Of  the  halogens  and  their  compounds, 
chlorine  is  most  commonly  employed.  It  may 
combine  directly  with  the  protoplasm  of  the 
organism,  thereby  coagulating  and  killing  it, 
at  the  same  time  decomposing  offensive  gases 
of  putrefaction,  such  as  sulphuretted  hydro- 
gen, phosphoretted  hydrogen,  and  ammonias  ; 
or,  which  is  the  more  common  and  important 
action  of  chlorine,  in  the  presence  of  water  it 
combines  with  hydrogen  to  form  hydrochloric 
acid  and  liberates  oxygen  ;  this  nascent  oxygen 
kills  bacteria  and  burns  up  putrescent  organic 
matter.  In  a  fluid  like  urine,  which  consumes 
large  quantities  of  chlorine,  excess  must  be 
maintained  until  the  last  germ  is  destroyed, 
that  is,  the  smell  of  chlorine  must  be  per- 
ceptible and  persistent  for  some  time.  The 
age  and  vitality  of  the  organism  influence  the 
length  of  time  required  for  sterilisation.  Inti- 
mate contact  between  the  gas  and  the  centre 
of  the  infected  mass  must  be  assured,  and  in 
this  requirement  chlorine  in  common  with 
all  gases  largely  fails  as  a  disinfectant.  In 
chloride  of  lime  and  hypochlorites  the  avail- 
able or  active  chlorine  is  that  present  in  the 
free  state  or  as  hypochlorite.  Chloros  is  a 
solution  of  sodium  hypochlorite  said  to  con- 
tain 10%  by  weight  of  chlorine.  In  the 
process  of  disinfection  by  these  bodies  hypo- 
chlorous  acid  is  formed  from  hypochlorite  by 


i  2 


BIS 


ENCYCLOPEDIA  OF 


DIS 


the  addition  of  an  acid  or  by  spontaneous 
action  of  atmospheric  carbon  dioxide ;  the 
hypochlorous  acid  splits  into  hydrochloric  acid 
and  nascent  oxygen,  which  latter  acts  as  the 
disinfectant.  The  great  fall  of  germicidal 
power  which  the  hypochlorites  experience  in 
the  presence  of  organic  matter  militates 
greatly  against  them  as  disinfectants. 

Hermite  solution  may  be  regarded  as  the 
magnesian  equivalent  of  chloride  of  lime. 
Sommerville  and  Walker  (see  Lancet,  Octo- 
ber 27,  1906)  conclude  that  the  available 
chlorine  in  this  fluid  diminishes  on  standing, 
is  rapidly  destroyed  in  the  presence  of  organic 
matter,  and  does  not  later  reappear.  The 
Eideal-Walker  co-efficient  of  the  fluid  was 
found  to  be  0'6  ;  using  urine  as  the  diluent, 
with  a  minute's  contact  0*075;  and  with  urine 
as  the  diluent  and  an  hour's  contact,  less  than 
O'Ol.  The  hypochlorites  of  this  fluid,  like  all 
other  hypochlorites,  are  unstable,  and  in 
presence  of  organic  matter  untrustworthy 
disinfectants. 

Perchloride  of  mercury  has  been  largely 
used  in  surgery,  and  is  a  powerful  disinfec- 
tant ;  but  it  is  also  a  powerful  poison,  doses  of 
0'2  gramme  per  diem  rapidly  causing  disas- 
trous effects.  It  dissolves  in  fifteen  parts  of 
water,  and  in  less  alcohol  and  ether.  If  the 
dissociation  of  metallic  ions  in  a  solution  of 
mercuric  chloride  be.  reduced  by  the  addition 
of  a  salt,  such  as  sodium  chloride,  its  germi- 
cidal power  is  likewise  reduced.  A  dilution 
of  1  in  1,000  is  recommended  for  non-sporing 
bacteria,  and  1  in  500  for  sporing  bacteria. 
The  biniodide  of  mercury  is  also  used  in 
surgery,  is  less  poisonous  than  the  per- 
chloride,  and  is  said  to  be  of  higher  germicidal 
efficiency.  Other  salts  of  mercury  in  use  are 
mercuric  cyanide,  mercuric  salicylate,  and 
mercuric  thymolate — all  poisonous,  difficult 
of  solution,  and,  as  they  coagulate  albumin, 
unable  to  penetrate  albuminous  envelopes. 

Where  the  organism  is  enclosed  in  a  protein 
or  fatty  envelope  those  disinfectants  which 
can  be  suspended  in  liquid  soaps  are  to  be 
selected,  and  it  should  ever  be  borne  in  mind 
that  the  solution  or  penetration  of  the  protein 


or  fatty  envelope  may  require  a  much  larger 
expenditure  of  energy  on  the  part  of  the 
disinfectant  than  the  killing  of  the  micro- 
organisms within.  In  all  such  work  it  is 
obvious  that  the  "oxidising"  disinfectants 
(permanganates,  peroxides,  hypochlorites,  &c.) 
are  undesirable.  In  a  set  of  experiments 
carried  out  by  Sommerville  and  Walker  a 
20%  solution  of  permanganate  of  potassium 
which  gave  a  co-efficient  of  50  in  water 
dropped  to  1'3  in  a  1%  solution  of  peptone, 
and  a  10%  solution  of  chloros,  acting  under 
the  same  conditions,  fell  from  21  to  0'2. 
Oxygen,  ozone,  and  peroxide  of  hydrogen 
labour  under  like  disadvantages. 

Oxygen,  the  natural  disinfectant,  burns  all 
organic  matter  into  carbon  dioxide,  water, 
&c.,  and  in  the  ordinary  or  molecular  form 
acts  slowly.  It  is  highly  active  when  liberated 
in  the  nascent  state  from  permanganates, 
peroxides,  &c.  The  intensity  of  its  action, 
however,  militates  against  its  disinfectant 
properties  when  the  bacteria  which  it  is 
intended  to  kill  are  embedded  in  organic 
matter,  seeing  that  it  spends  its  energy  on  the 
latter.  Ozone  readily  decomposes  into  mole- 
cular oxygen  and  nascent  oxygen,  and  is 
mostly  prepared  for  disinfection  purposes 
from  air  by  the  passage  of  an  electric  dis- 
charge. Peroxide  of  hydrogen  is  readily 
prepared  from  a  peroxide  of  an  alkaline  earth 
and  an  acid :  Ba02  +  H2S04  =  BaS04  +  H202 
This  is  a  syrupy  liquid  which  readily  decom- 
poses into  water  and  nascent  oxygen. 

Of  organic  bodies  the  paraffin  and  aromatic 
series  furnish  the  disinfectants  most  impor- 
tant in  practice.  Formalin,  a  40%  aqueous 
solution  of  formic  aldehyde,  is  the  most 
important  of  the  paraffin  group.  It  may  be 
used  in  liquid  or  gaseous  form,  but  the  gas 
is  practically  useless  unless  precautions  are 
taken  to  obtain  in  the  room  to  be  disinfected 
the  necessary  degree  of  moisture,  tempera- 
ture, quantity  of  formaldehyde  (which  should 
be  not  less,  perhaps,  than  100  grammes  per 
1,000  cu.  ft.),  and  complete  sealing  from  the 
outside  atmosphere. 

Of  the  aromatic  series  the  best  known  is 


116 


DIS 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


DIS 


phenol.  It  is  generally  stable  in  the  presence 
of  organic  matter,  but  is  poisonous  and  caustic, 
and  for  the  disinfection  of  spores  useless. 
Crude  carbolic  acid  consists  of  cresols  and 
higher  phenols  in  various  proportions,  depen- 
dent on  the  source  of  the  tar.  Cresols  are 
with  difficulty  soluble  in  water,  and  in  alcohol 
or  oil  have  little  germicidal  power ;  they  are 
much  depreciated  in  efficiency  by  proteins. 
The  addition  of  salt  solution  or  mineral  acid 
enhances  the  disinfectant  values  of  phenol  and 
cresols,  and  the  latter  may  be  conveniently 
dissolved  in  alkalies.  A  number  of  saponified 
neutral  tar  oils,  known  commercially  as 
soluble  carbolic  acid,  soluble  creosote,  &c.,  is 
met  with  in  practice,  but  the  efficiency  in  all 
cases  is  low.  Lysol  appears  to  be  a  solution 
of  cresols  in  fatty  acid  saponified  with  addition 
of  alcohol.  It  produces  a  clear  solution  in 
water.  Izal  is  described  as  a  preparation  of 
oxidised  hydrocarbons  obtained  from  coke 
ovens.  It  is  much  less  poisonous  and  caustic 
than  phenol,  and  has  a  much  greater  germi- 
cidal power.  Cyllin  is  described  as  prepared 
from  certain  members  of  a  new  series  of 
oxidised  hydrocarbons  extracted  from  coal-tar, 
and  is  emulsified  so  as  to  be  miscible  in  all 
proportions  in  water.  Its  toxicity  is  extremely 
low,  and  germicidal  efficiency  high. 

Cofectant,  a  still  more  modern  preparation, 
is  exquisitely  emulsified  and  of  high  and  con- 
stant efficiency.  Its  toxicity  is  negligible. 

Disinfectant  powders  may  have  some  value 
when  they  possess  a  soluble  base,  otherwise, 
except  as  deodorants,  they  are  useless.  The 
only  practicable  base  is  lime,  and  as  this  is 
incompatible  with  phenol,  it  is  necessary  to 
use  a  high  class  disinfectant  of  different  type ; 
such  disinfectant  may  be  found  in  the  aroma- 
tic group.  It  must  not  be  forgotten,  however, 
that  the  germicidal  powers  of  the  best  possible 
powders  are  necessarily  small  when  compared 
with  liquids. 

Experimental  work  on  the  bacteriological 
standardisation  of  disinfectants  during  the 
past  five  years  has  brought  to  light  the 
superior  efficiency  of  certain  emulsified  coal- 
tar  products.  It  is  possible  to  prepare  such 


emulsions  so  as  to  possess  a  germicidal 
efficiency  fifteen  or  sixteen  times  that  of 
phenol,  when  tested  by  the  Rideal-Walker 
method,  or  ten  to  twelve  times  that  of  phenol, 
when  subjected  to  the  Sommerville- Walker 
test. 

Until  recently  the  merest  empiricism  has 
characterised  the  use  of  disinfectants.  In 
future,  discrimination  will  be  used  in  selecting 
a  suitable  type  of  disinfectant  for  a  particular 
form  of  work,  and  in  order  to  obtain  the  best 
results  all  the  conditions  attaching  to  the 
work  to  be  done  will  be  intimately  studied. 
It  has  been  amply  demonstrated  that,  except 
in  a  very  few  cases,  the  quantitative  estima- 
tion of  the  so-called  active  chemical  principle 
furnishes  little  information  concerning  germi- 
cidal efficiency.  Previous  to  1903,  when 
Rideal  and  Walker  brought  forward  their 
bacteriological  method  of  testing  disinfectants, 
too  much  attention  had  been  paid  to  the 
quantity  of  chemically  active  principle  present 
in  disinfectants,  whilst  the  form  in  which  it 
existed  was  practically  ignored  ;  chemical 
analysis  was  accordingly  the  main  criterion 
by  which  the  value  of  a  preparation  was  esti- 
mated. In  bacteriology,  as  in  all  sections  of 
biology,  the  estimation  of  effects  produced  on 
any  unit  or  set  of  units  by  external  conditions 
involves  the  careful  consideration  of  a  number 
of  variable  factors.  But  if  in  a  given  series  of 
experiments  one  observer  considers  the  time 
of  application  of  the  agent  the  only  important 
factor,  a  second  the  proportion  of  culture  to 
disinfectant,  and  so  on  throughout,  no  two 
results  can  be  compared.  Uniformity  of  pro- 
cedure in  every  step  of  the  investigation  must 
be  a  sine  qua  non  where  comparison  of  results 
is  required.  Rideal  and  Walker  in  their 
method  lay  it  down  as  axiomatic  that  in 
selecting  any  particular  process  to  be  employed 
as  a  standard  the  following  factors  must  be 
considered  : — (1)  Time  of  medication  and 
incubation.  (2)  Age  of  the  bacterial  culture  ; 
the  resistance  of  different  micro-organisms 
varies  in  different  degrees  according  to 
age.  (3)  Choice  of  medium  and  its  reaction  ; 
broth  cultures  possess  certain  advantages 


117 


DIS 


ENCYCLOPAEDIA  OF 


DIS 


over  cultures  raised  on  solid  media ;  the 
standard  broth  used  for  the  growth  of  the 
B.  typhosus  possesses  an  acidity  of  +  1'5%. 
(4)  Temperature  of  medication;  within  certain 
limits  the  higher  the  temperature  at  which 
disinfectants  act  the  greater  the  germicidal 
efficiency.  (5)  Temperature  of  incubation ; 
all  organisms  have  an  optimum  temperature 
of  growth  at  which  temperature  they  are  most 
vigorous.  (6)  Variations  in  vital  resistance 
of  the  same  species ;  sub-cultures  of  organisms 
on  different  media  possess  different  degrees  of 
resistance,  as  do  also  cultures  obtained  from 
different  sources.  (7)  Variations  in  vital 
resistance  of  different  species  ;  for  the  most 
part  disinfectants  give  different  co-efficients 
when  tested  against  different  organisms.  (8) 
Proportion  of  culture  to  disinfectant  ;  the 
slightest  deviation  from  uniformity  in  this 
factor  makes  the  test  worthless. 

The  efficiency  of  the  disinfectant  is  expressed 
in  terms  of  phenol  doing  the  same  work  as  the 
Kideal-Walker  co-efficient.  Whilst  much  has 
been  written  on  methods  of  estimating  avail- 
able chlorine  in  bleaching  powders,  crystallis- 
able  phenols,  cresols,  tar  oils,  and  water  in 
preparations  of  carbolic  acid,  &c.,  &c.,  it 
cannot  be  too  emphatically  stated  that  all 
such  tests  are  vain,  and  that  direct  appeal  to 
bactericidal  powers  alone  avails.  (See  section 
dealing  with  Bacteriological  Examination  of 
Disinfectants.) 

With  a  view  to  imitating  conditions  that  ob- 
tain in  practical  disinfection,  Sommerville  and 
Walker,  in  1906,  attempted  to  grow  the  B.  typho- 
sus in  various  forms  of  sterile  organic  matter, 
such  as  urine,  blood,  blood  serum,  mucin, 
gelatin,  pus,  &c.,  and  then  to  add  the  various 
disinfectants  in  suitable  dilutions  to  measured 
quantities  of  these  organic  media,  and  finally 
to  plant  out  in  broth  after  the  manner  of  the 
Eideal-Walker  method.  But  several  trials 
demonstrated  that  the  B.  typhosus  grew  so 
feebly  in  these  media  that  it  was  impossible 
to  obtain  uniform  results.  Later  they  pointed 
out  that  uniform  results  could  be  obtained  by 
diluting  the  disinfectants  under  test  with  an 
emulsion  of  "5%  gelatin  and  '5%  rice  starch. 


The  starch  was  used  to  meet  the  influence  of 
adsorption.  The  presence  of  this  amount  of 
animal  and  vegetable  matter  lowered  the  co- 
efficients of  different  disinfectants  to  different 
degrees,  but  in  each  case  always  to  the  same 
degree. 

It  is  not  to  be  concluded  that  the  figure 
obtained  (Sommerville  -  Walker  co  -  efficient) 
indicates  in  any  measure  the  quantity  of 
disinfectant  to  be  used  in  any  given  case ;  it 
merely  shows  the  relative  fall  of  co-efficient 
of  a  disinfectant  under  the  conditions  of 
admixture  with  organic  matter  described,  as 
compared  with  phenol  under  the  same  con- 
ditions. In  this,  as  in  many  other  problems 
in  which  exact  quantitative  data  cannot  be 
obtained,  a  liberal  use  must  be  made  of  "  the 
factor  of  safety."  D.  S. 

Disinfection  Stations  and  Appliances. 

— 1.  Local  authorities  have  power  to  provide 
and  equip  disinfection  stations  and  to  disinfect 
free  of  charge  any  articles  brought  there  for 
the  purpose.  They  must  exercise  their  power 
to  disinfect  or  destroy  any  articles  as  to  which 
the  Medical  Officer  of  Health  or  any  other 
legally  qualified  medical  practitioner  certifies 
that  their  disinfection  or  destruction  would 
tend  to  prevent  or  check  the  spread  of  any 
dangerous  infectious  disease,  unless  the  master 
or  owner  of  the  house  undertakes  the  duty 
within  24  hours  from  receiving  notice  from 
the  local  authority  and  carries  out  his 
undertaking.  For  the  purpose  of  such  disin- 
fection the  local  authority  may  enter  any 
premises  by  day  (6  a.m.  to  9  p.m.).  The 
disinfection  must  be  carried  out  at  the  cost  of 
the  local  authority,  under  the  superintendence 
of  its  Medical  Officer  of  Health,  and  compen- 
sation must  be  given  to  the  master  or  owner 
of  articles  which  have  been  damaged  unneces- 
sarily in  the  process  of  disinfection.  On  the 
application  of  any  person,  local  authorities 
may  pay  the  expenses  of  disinfecting  any 
bedding,  clothes,  or  other  things  which  have 
been  exposed  to  infection,  provided  such  disin- 
fection is  carried  out  by  the  local  authority 
or  under  its  direction. 


118 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


DIS 


On  notification  from  any  person  that  a  book 
in  his  possession  belonging  to  a  public  or 
circulating  library  has  been  exposed  to  notifi- 
able infectious  disease,  the  local  authority 
must  cause  such  book  to  be  disinfected  or 
destroyed,  paying  to  the  proprietor  the  value 
of  any  book  destroyed.  When  a  person 
suffering  from  a  notifiable  infectious  disease 
has  been  driven  in  a  public  vehicle  without 
the  knowledge  of  the  owner  or  driver  that  the 
person  was  so  suffering,  the  owner  or  driver 
may  require  the  local  authority  to  disinfect 
the  vehicle  and  its  contents  free  of  charge. 
The  local  authority  may  provide  apparatus 
for  destruction  of  vermin,  and  allow  it  to  be 
used  free  of  charge  by  any  persons  declaring 
themselves  to  be  infested  with  vermin.  Such 
apparatus  consists  essentially  of  a  steam  disin- 
fector  for  clothing  and  baths  for  persons. 

Ships  or  boats  in  rivers,  harbours,  or  other 
waters  within  the  jurisdiction  of  a  local 
authority,  are  reckoned  for  disinfection  pur- 
poses as  houses,  the  master,  or  other  officers 
in  charge,  being  deemed  the  occupier.  If  not 
within  the  district  of  a  local  authority  the 
Local  Government  Board  may  prescribe  a 
district  to  undertake  the  duty,  and  in  default 
of  such  prescription  it  must  be  undertaken  by 
the  nearest  district.  Admiralty  and  War 
Office  property  are  exempt  from  the  jurisdic- 
tion of  the  local  authority,  unless  by  consent. 
The  Local  Government  Board  may  authorise 
or  require  any  two  or  more  local  authorities 
to  combine  for  the  purpose,  inter  alia,  of 
disinfection. 

In  addition  to  the  normal  powers  and  duties 
of  a  local  authority,  of  which  the  effect  is 
summarised  above,  special  regulations  may 
be  made  by  the  Local  Government  Board  on 
the  occurrence  of  cholera  or  any  other 
epidemic,  endemic,  or  infectious  disease,  or 
on  any  part  of  England  appearing  to  be 
threatened  or  being  affected  by  any  formid- 
able outbreak.  These  regulations  may  be 
revoked  or  modified,  and  the  period  of  their 
application  extended  or  abridged ;  and  the 
local  authority  of  any  district  within  which 
or  part  of  which  such  regulations  are  declared 


to  be  in  force  must  superintend  and  see  to 
their  execution,  and  appoint  and  pay  any 
necessary  medical  or  other  officers,  and  do  all 
things  necessary.  For  practical  purposes,  a 
local  authority  has,  therefore,  to  provide  for 
the  disinfection  of  all  articles  liable  to  retain 
infection,  whether  in  normal  times  or  during 
epidemics  ;  and  in  view  of  the  difficulty  of 
ensuring  proper  disinfection  of  goods,  such  as 
rags  used  for  industrial  purposes,  they  may 
find  it  expedient  to  undertake  such  disinfection 
for  themselves. 

2.  The  construction  of  a  disinfection-station 
should  fulfil  the  following  conditions  :  (a)  The 
disinfection  room  should  be  divided  into 
separate  chambers  for  infected  and  dis-infected 
material  respectively.  No  direct  passage  of 
men  or  material  from  the  infected  to  the  dis- 
infected side  should  be  possible  except  through 
the  steam  disinfector  itself.  For  this  purpose 
the  room  is  divided  by  a  solid  wall  or  parti- 
tion through  which  the  disinfector  projects  in 
each  direction.  A  window  may  be  let  into 
this  wall  to  enable  persons  employed  on  one 
side  to  see  and  signal  to  those  on  the  other. 
The  best  means  of  providing  access  from  the 
infected  to  the  disinfected  side  is  to  arrange 
exits  on  the  side  wall  of  each  space  leading 
into  lobbies  which  communicate  through  doors 
with  a  bath-room  fitted  with  a  water-basin. 
Each  of  the 'lobbies  has  a  set  of  overalls  and 
felt  slippers  for  each  man,  which  he  puts  on 
as  he  passes  into  the  corresponding  side  of 
the  disinfection  room,  and  takes  off  as  he 
passes  out  from  it,  washing  his  hands  and 
face  as  he  passes  through  the  bath-room.  At 
the  end  of  the  day  the  clothes  and  slippers  are 
passed  through  the  disinfector  and  returned 
to  their  proper  places.  The  use  of  overalls 
and  of  washing  is  of  some  importance  in 
reducing  the  risk  of  disinfected  objects  becom- 
ing reinfected.  Its  chief  value,  however,  lies 
in  the  fact  that  at  the  cost  of  comparatively 
little  trouble  it  is  an  automatic  drill  for  the 
disinfector  attendants  in  the  caution  which 
they  must  exercise  if  their  work  is  to  be 
effective,  (b)  The  space  allotted  to  the 
infected  side  should  be  no  greater  than  will 


119 


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ENCYCLOPEDIA  OF 


DIS 


accommodate  the  goods  to  be  treated,  facilities 
for  storing,  and  thus  delaying  their  treatment, 
being  undesirable.  The  disinfected  side,  in 
which  the  working  fittings  of  the  disinfector 
should  be  arranged,  should  be  of  ample  size, 
with  convenience  for  airing  and  storing  dis- 
infected objects,  (c)  The  internal  facings  of 
all  walls,  floors,  and  ceilings  should  be  smooth, 
impervious,  free  from  angl'es  and  as  far  as 
possible  from  joints,  unaffected  by  damp,  and 


separate  as  in  the  case  of  the  infected  and 
disinfected  sides  of  the  disinfection  room.  All 
surfaces  in  a  collection  van  should  be  water- 
proof and  free  from  seams  and  angles,  so  that 
it  can  be  thoroughly  washed  with  a  strong 
soap-disinfectant  at  the  end  of  each  day. 
Where  only  one  van  is  used,  or  no  separation 
is  maintained  between  vans  for  collection  and 
for  delivery,  the  van  after  disinfection  at  the 
end  of  the  day  should  be  kept  on  the  disinfected 


H.  J.  MUH  T£N .  (A.  M.  ha.  C.E.  I 
Survtyor, 

fir.  BOM.  fHNOSWOHTH . 


I         I  Steaai  Tra/t.  . 
]  Steam  Treyt. 

' -,  r 


FIG.  1. — Disinfecting  Station,  Tooting,  S.W. 


reely  guttered  and  drained  so  as  to  allow  of 
copious  flushing,  (d)  All  parts  of  the  building 
should  be  well  lighted ;  skylights  should  pre- 
ferably be  double  to  avoid  the  risk  of  condensa- 
tion and  dripping.  The  windows,  &c.,  should 
be  arranged  to  give  thorough  ventilation,  but 
to  avoid  draughts  in  the  neighbourhood  of  the 
disinfector  and  the  disinfected  clothes.  It  is 
convenient  as  well  as  desirable  on  other 
grounds  to  have  two  vans,  one  being  reserved 
for  collection  of  infected  goods  and  the  other 
for  delivery  of  disinfected  goods.  Where  this 
is  practicable,  the  stables  should  be  kept 


side.  Where  the  van  does  more  than  one 
journey  in  the  day,  it  must  be  washed  with 
strong  soap-disinfectant  after  each  journey. 
The  courtyards  should  be  asphalted  or  con- 
creted to  allow  of  free  flushing. 

3.  The  most  important  equipment  in  a 
disinfection-station  is  the  steam-disinfector. 
Considerable  use  was  made  of  steam-disinfec- 
tion before  the  facts  which  affect  their 
efficiency  were  known  ;  and  very  many  stations 
are  equipped  with  steam-disinfectors  which 
give  no  certainty  of  real  disinfection,  and  are 
probably  doing  some  mischief  through  the 


120 


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MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


DIS 


false  confidence  which  they  engender.  Com- 
plete disinfection  of  all  organisms  in  practical 
conditions  can  be  obtained  only  by  the  use  of 
saturated  steam,  free  from  air  and  applied  at 


originally  in  the  disinfector  must  be  displaced 
by  or  blown  out  with  the  steam  which  enters ; 
that  is  to  say,  the  steam  must  be  applied  as  a 
current  until  the  air  in  the  chamber  has  been 


a  pressure  of  10  to  20  Ibs.  per  square  inch  for  a  removed.  The  use  of  what  is  sometimes 
period  which  for  ordinary  objects  varies  from  called  a  "vacuum,"  but  in  fact  is  a  partial 
15  to  30  minutes.  The  omission  of  any  of  vacuum  only,  removes  a  part  of  the  air.  A 


faoM    PIT  AT 
LOWEST          END 


2. — Showing  Plan  of  Disinfecting  Machine  and  arrangement  of  Steam  Pipes. 


these  conditions  may  at  any  time  cause 
failure  of  disinfection.  This  danger  is  the 
more  serious  because,  when  failure  occurs,  it 
is  seldom  possible  to  trace  the  return  case  to 
the  real  cause  ;  and  expense  may  be  incurred 
through  continuance  of  an  epidemic  and 
through  precautions  against  some  innocent 
assumed  cause,  which  might  have  been  spared 
by  correct  design  of  the  disinfector. 

To    obtain   steam   free   from    air,    the   air 


"  good  vacuum  "  of  this  character  corresponds 
to  some  20  in.  of  mercury,  and  thus  leaves 
one-third  of  the  air  in  the  disinfector ;  a  mix- 
ture much  less  efficient  for  disinfection  than 
pure  steam.  Apart  from  the  air  in  the  dis- 
infector, a  certain  amount  will  remain  in  the 
pores  of  the  mattresses  and  other  thick  objects  ; 
this  air  is  removed  by  periodically  blowing  off 
steam  from  the  disinfector  after  it  has  been 
allowed  to  reach  the  necessary  pressure  and 


121 


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ENCYCLOPAEDIA   OF 


DI8 


has  remained  at  it  for  a  few  minutes.  Satu- 
rated steam  is  usually  obtained  from  an 
ordinary  vertical  boiler.  It  should  be  passed 
through  a  separator  before  being  admitted  to 
the  disinfector,  so  as  to  avoid  the  admission  of 
pre-formed  water,  which  retards  the  penetra- 
tion of  heat  and  the  ultimate  drying  of  the 
objects  under  treatment.  When  the  boiler 


in  each  operation  should  always  be  secured 
independently  of  the  attendant.  While  involv- 
ing no  sensible  addition  to  the  cost  of  working 
and  not  much  to  the  first  cost  of  the  plant, 
the  use  of  this  precaution  is  convenient  to  the 
attendant  in  giving  him  a  record  of  what  he 
is  doing.  It  is  still  more  convenient  to  the 
officer  responsible  for  the  station,  not  only  in 


DlS/ffFECTED 

GOODS 


INFECTED     GOODS 


CLOSED 

//V     0/V£ 
fJXED      4  '.  6  "  Ff>  OAf 
CftOU/VO      LEVEL 


WOOD      Off   IKON    COVE  ft 
P/T        NOT    Suf-^LlED    BY 
M  A  &    C°Lf 


FIG.  3. — Plan  of  Disinfecting  Machine. 


forms  part  of  the  disinfector,  care  must  be 
taken  to  see  that  the  steam  is  not  superheated 
by  excessive  transmission  of  heat  from  the 
furnace-gases  through  the  shell  of  the  steam- 
space.  This  defect  occurs  in  many  self- 
contained  disinfectors,  and  prevents  uniform 
heating  and  complete  disinfection.  It  also 
gives  rise  to  scorching  of  goods,  which  subjects 
the  authority  to  claims  for  compensation. 

The  assurance  that  all  the  necessary  con- 
ditions for  true  disinfection  have  been  attained 


giving  him  direct  proof  that  the  disinfector 
has  been  worked  efficiently,  but  also  in 
enabling  him  to  exhibit  this  proof  to  others. 
The  most  satisfactory  way  of  obtaining  this 
control  is  to  connect  a  by-pass  from  the  dis- 
infector to  a  gauge  which,  when  the  steam  in 
the  disinfector  is  free  from  air,  permits  the 
steam  in  the  by-pass  to  enter  a  recording 
pressure-gauge,  on  which  it  traces  a  curve 
indicating  the  pressure  attained  and  the 
period  of  exposure.  When  the  operation  is 


122 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


DIS 


interrupted,  as,  for  instance,  on  blowing  off 
for  the  ejection  of  air  from  the  pores  of  mat- 
tresses, the  by-pass  closes  automatically,  and 
the  freedom  of  the  steam  from  air  has  to  be 
verified  again  before  the  steam  can  pass  to  the 
recording  gauge  and  give  credit  for  further 
disinfection.  The  apparatus  is  usually 
arranged  to  be  worked  merely  by  pushing  or 


detached  and  the  pores  to  be  filled  with  dry 
air  more  readily  than  after  they  have  cooled. 
Where  considerable  variations  are  likely  to 
occur  in  the  amount  of  work  to  be  done  at  a 
station,  it  is  possible  to  economise  in  steam 
by  installing  two  disinfectors,  of  which  one 
serves  to  do  the  normal  work  and  the  other 
the  excess.  In  such  installations  it  is  usually 


AfOTE .    AFTER    DISINFE.CTOR 
POSITION     THE    SPACE 
ARCHWAY     <&    OISINFECTOR    TO  B£ 
FILLED    /M   WITH    BRICK,    W/TH   A 
LAYER     of    f£LT  PLACED  BE 

D/SlMFECTOf*    «£     BRICKWORK 


FIG.  4.  —  Section  of  Disinfecting  Machine. 


pulling  a  button,  and  its  use  involves  no  skill 
whatever.  In  most  disinfectors  means  are 
provided  for  drying  thick  objects,  and  it  is 
very  important  that  they  should  be  rapid  and 
efficient,  so  as  to  avoid  scorching  and  damp- 
ness. Immediately  on  removing  the  objects 
from  the  disinfector  they  should  be  thoroughly 
shaken  and  hung  up  or  laid  out  to  air,  as 
their  relative  high  temperature  enables  the 
film  of  steam  which  hangs  about  them  to  be 


better  to  have  two  sizes  of  disinfector,  say 
7  ft.  6  in.  by  4  ft.  3  in.  diameter  and  9  ft.  by 
6  ft.  diameter.  An  alternative  method  of 
getting  excess  of  work  out  of  a  disinfector  is 
to  have  an  auxiliary  drying  closet,  which  is 
used  to  relieve  the  disinfector  for  the  period 
ordinarily  occupied  in  drying.  With  this 
arrangement  the  drying  closet  must  be  larger 
than  the  volume  of  the  disinfector  which  it 
relieves,  as  the  transfer  of  goods  from  the 


123 


DI3 


ENCYCLOPAEDIA   OP 


DIS 


disinfector  to  the  closet  entails  a  certain 
amount  of  condensation  and  a  proportionately 
longer  period  of  drying.  Given  such  a  closet, 
the  work  done  by  a  good  disinfector  may  be 
approximately  doubled  when  it  is  relieved 
from  the  duty  of  drying.  A  drying  closet 
may  be  worked  with  a  fan  or  by  natural 
ventilation,  and  is  best  furnished  with 
"  horses  "  to  draw  out  as  in  laundry  practice. 
The  disinfector  should  drain  into  a  steam 
trap,  to  avoid  nuisance  and  loss  from  escaping 
steam.  If  drying  coils  are  used  with  steam 
at  a  higher  pressure,  a  separate  steam-trap 
will  be  required.  If  the  exhaust  from  the 
disinfector  is  a  nuisance,  it  may  be  fitted  with 
a  condensing  silencer.  The  disinfector  and 
boiler  should  be  thoroughly  well  lagged  to 
reduce  the  loss  and  inconvenience  due  to 
escape  of  heat.  A  disinfector  should  always 
be  warm  before  goods  are  put  in  it  for  treat- 
ment, and  they  should  be  removed  as  soon  as 
the  operation  is  over.  Where  the  funds 
necessary  for  a  disinfector  for  absolute  dis- 
infection are  not  available,  a  low-pressure  or 
a  non-pressure  disinfector  must  be  used.  The 
design  of  such  a  disinfector  must  be  such  as 
to  drive  the  fastest  possible  current  of  steam 
through  the  disinfecting  chamber.  Longer 
time  must  be  allowed  both  for  disinfection 
and  for  drying  them  in  disinfectors  working 
at  higher  temperatures.  Such  disinfectors 
are  perfectly  sufficient  for  dealing  with  enteric 
fever,  diphtheria,  cholera,  and  certain  other 
diseases  associated  with  sporeless  organisms. 
There  is  no  evidence  that  they  can  be  depended 
on  to  disinfect  from  small-pox,  scarlet-fever, 
or  measles.  Steam  for  a  disinfector  may  be 
derived  from  a  neighbouring  destructor  station. 
In  this  and  other  cases  in  which  steam  is 
brought  to  the  disinfector  from  a  distance  the 
efficiency  of  drying  and,  to  some  extent,  of 
disinfection  depends  largely  on  the  pipe-run 
being  well  designed  arid  the  pipes  thoroughly 
lagged. 

4.  The  accessory  appliances  needed  for  a 
disinfection  station  are :  (a)  convenient  racks 
for  airing  and  stacking  disinfected  objects. 
The  best  airing  racks  are  of  steam-heated 


tinned  copper  pipes.  They  are  more  costly  than 
wood,  but  take  less  labour  to  keep  clean,  last 
longer,  and  are  much  more  rapid  in  operation. 
(b)  A  small  tank  for  chemical  disinfectant, 
such  as  permanganate  of  potash,  so  that  spots 
of  organic  matter  may  be  damped  before  steam- 
disinfection,  to  prevent  them  from  leaving 
fixed  stains,  (c)  A  boiling  tank  for  objects 
too  stained  with  organic  matter  to  make  it 
desirable  to  go  over  them  with  cold  disin- 
fectant. Such  a  tank  is  preferably  made  in 
two  parts,  one  over  the  other,  communicating 
by  two  tubes  which  enter  the  lower  tank  at 
different  levels,  and  arranged  so  that  the 
liquid  contents  of  the  lower  tank  boil  up  into 
the  upper  tank  and  there  steep  the  clothes, 
&c.,  circulating  continuously  from  lower  to 
upper  tank,  and  ultimately  falling  back  into 
the  lower  tank  at  the  end  of  the  operation. 
This  construction  ensures  the  constant  expo- 
sure of  the  clothes  to  boiling  water  ;  and  by 
putting  washing  soda  in  the  lower  vessel  both 
the  temperature  of  the  boiling  water  and  its 
cleansing  power  are  raised  to  a  very  valuable 
extent.  Where  practicable  the  tank  should 
be  arranged  like  the  disinfector  through  the 
partition  wall,  the  goods  being  slid  in  under 
water  from  the  infected  side  and  taken  out  on 
the  disinfected  side,  (d)  A  spray  disinfector 
for  dealing  with  objects  such  as  furs,  leather, 
&c.,  which  cannot  stand  steam,  (e)  Hose  and 
flushing  apparatus  enabling  all  parts  of  the 
station  to  be  flushed  down.  (/)  Bath  and 
basins  for  attendants  with  hot  and  cold  water. 
If  cleansing  of  persons  is  undertaken,  two 
other  separate  baths,  for  men  and  women 
respectively,  should  be  provided  in  a  room 
adjacent  to  the  disinfector  room,  so  that  the 
clothes  of  persons  may  be  disinfected  and 
deverminised  while  they  are  in  the  bath. 
(g)  A  store  for  the  utensils  (spray-disinfectors, 
brushes,  bottles,  soap,  &c.),  served  out  to  the 
house-disinfectors  in  their  daily  rounds,  (h) 
An  incinerator  for  burning  objects  not  worth 
disinfection.  W.  D. 


Distemper.  —  A    water    paint    made    by 
mixing   refined   chalk    with    water    and   an 


124 


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MUNICIPAL   AND   SANITAKY  ENGINEERING. 


DIS 


agglutinant  such  as  ordinary  size,  colour 
being  added  when  desired.  Ordinary  white- 
wash is  an  example  of  a  distemper.  Of  late 
years  ordinary  distempers  are  being  used  less 
than  formerly,  their  place  being  taken  by 
washable  water  paints  or  distempers.  (See 
"  PAINTS  AND  PAINTING.") 

Distributors,  for  Sewage.— An  essential 
feature  of  the  "  percolation  bed  "  for  the  dis- 
posal of  sewage  lies  in  distributing  the  liquid 
uniformly,  and  at  a  suitable  rate,  over  the 
whole  of  the  surface  of  the  bed,  so  that  it 
may  percolate  through  by  dripping  slowly 
from  particle  to  particle  of  the  filtering 
material  and  thus  become  thoroughly  exposed 
to  the  air  and  the  nitrifying  influences  of  the 
bed.  This  object  is  accomplished  in  a  variety 
of  ways,  that  most  generally  adopted  being 
distribution  by  means  of  a  continuous  rain- 
like  shower  from  revolving  "  sprinklers " 
working  in  a  horizontal  plane  on  the  Barker's 
mill  principle,  or  by  means  of  "jets"  or 
nozzles  placed  in  rows  of  fixed  pipes  carrying 
the  sewage  under  a  head  of  from  5  to  about 
10  ft.  In  some  cases  the  same  object  is 
sought  by  the  employment  of  distributors 
travelling  on  rails  and  carrying  a  series  of 
buckets  or  nozzles  arranged  to  embrace  the 
full  width  of  the  bed.  At  small  works  distri- 
bution has  also  been  affected,  with  varying 
degrees  of  success,  by  means  of  balanced 
trays  or  tippers,  and  sheet-iron  gutters  or 
troughing.  Whatever  form  of  distributor  is 
adopted,  it  is  important  that  it  should  distri- 
bute the  liquid  uniformly  without  interrup- 
tions from  wind,  frost,  or  other  atmospheric 
conditions,  that  it  should  not  easily  stop 
through  clogging  of  small  holes  and  that  it 
should  be  easily  and  quickly  cleaned.  It 
should  be  self-adjusting  to  variations  of  flow, 
and  the  bearings  and  central  moving  parts 
through  which  the  sewage  is  admitted  should 
be  of  special  and  appropriate  design.  The 
means  first  adopted  for  distributing  sewage 
over  percolating  filters  consisted  in  the  use  of 
a  fine  surface  material  over  which  the  sewage 
was  flushed  and  distributed  by  flooding.  The 


result,  however,  was  not  satisfactory  as  the 
top  layer  and  coating  greatly  impeded  aera- 
tion and  led  to  unevenness  of  distribution. 
Trials  were  also  made  with  both  wooden  and 
iron  troughs  provided  with  holes  and  notches 
placed  over  the  surface  of  the  bed  at  intervals 
of  2  or  3  ft.,  but  the  difficulties  of  keeping 
these  level  and  the  notches  clear  contributed 
largely  to  unevenness  and  cost  of  distribution 
insomuch  that  the  system  is  found  almost 
impracticable  except  for  small  installations. 
A  greatly  improved  iron  trough  and  tipper 
arrangement  has  been  introduced  by  W.  E. 
Farrer,  of  Birmingham.  "With  the  object  of 
securing  more  constant  and  uniform  distribu- 
tion than  is  obtained  by  troughs,  a  distributor, 
constructed  of  a  special  form  of  corrugated 
iron  sheets,  was  introduced  by  F.  Stoddart, 
of  Bristol,  and  over  this  the  sewage  runs 
from  the  main  carrier  into  small  channels 
formed  by  the  corrugations.  The  sheets 
are  punched  with  numerous  holes  to  allow  the 
sewage  to  drip  through  uniformly  on  to  the 
beds  from  a  great  number  of  small  points  thus 
provided.  It  is  necessary,  however,  that  the 
sheets  should  be  absolutely  level  and  the  holes 
kept  clear  from  obstruction  by  frequent 
brushing.  At  Lichfield,  about  the  year  1898, 
a  system  of  perforated  pipes,  working  under 
pressure  as  suggested  by  Mr.  Garfield,  was 
introduced  and  has  since  been  working  satis- 
factorily. The  "  jets  "  work  under  a  head  of 
7  ft.,  and  the  sewage  is  discharged  in  fine 
sprays  by  the  use  of  small  metal  plates  placed 
over  each  jet  upon  which  the  liquid  impinges 
and  is  thus  scattered  over  a  wide  area.  The 
whole  series  of  distributing  pipes  are  so 
arranged  that  they  can  be  turned  through  an 
angle  of  45°  and  the  jets  thrown  first  on  one 
side  of  the  tube  and  then  on  the  other,  thus 
securing  a  good  and  even  distribution.  A 
somewhat  similiar  arrangement  is  in  use  at 
Chesterfield,  but  here  the  quantity  of  sewage 
is  varied  from  time  to  time  by  an  automatic 
ejector.  The  liquid  as  it  impinges  on  the  iron 
plates  over  the  holes  in  the  distributing  pipes 
is  thrown  in  a  circle  all  around,  the  radius  of 
which  narrows  as  the  head  or  pressure  from 


125 


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DIS 


the  ejector  diminishes,  so  that  each  part  of 
the  filter  is  alternately  sprinkled.  Perforated 
distributing  pipes  are  also  used  successfully 
at  Brownhills  and  Pelsall  in  Staffordshire. 
Here  the  available  head  is  less  than  a  foot 
and  no  effort  is  made  to  spray  the  jets,  but 
the  surface  of  the  filter  is  formed  into  low 


iron  distributing/ 
pipe  drilled 
for  rwzzles 


FIG.  1. — Gjer's  &  Harrison's  Nozzle 
used  at  Salford. 


ridges  between  which  the  distributing  pipes 
are  placed.  At  Salford,  sprinkling  filters 
were  first  constructed  in  1899,  and  have  been 
added  to  from  time  to  time.  The  precipi- 
tating tank  liquor  is  passed  through  roughing 
filters  of  2  in.  to  \  in.  mixed  gravel,  to  hold 
back  suspended  matters  find- 
ing their  way  through  the 
tanks,  and  is  then  distributed 
over  percolation  beds  of 
clinkers  of  an  average  depth 
of  about  5  ft.,  by  means  of 
4  in.  fixed  pipe  distributors 
in  which  sprinkling  "  jets  " 
are  placed  working  under  a 
4  ft.  head.  Figs.  1  and  2 
illustrate  the  description  of 
nozzles  used.  The  Salford 
aerating  filters  deal  with  the 
roughing  bed  liquor  at  the 
rate  of  500  gallons  per  square 
yard  on  filters  5  ft.  deep,  or 
equal  to  278  gallons  per  cubic  yard  of  filtra- 
tion material ;  in  some  cases  this  rate,  though 
large,  has  been  exceeded. 

FIXED  SPRAY  JETS. — The  best  example  of 
the  extensive  use  of  fixed  spray  jets  of  good 
pattern  is  on  the  works  of  the  Birmingham 


FIG.  2. 
Sewage    Spray 
Nozzle,  used 
at  Salford. 


Tame  and  Eea  Drainage  Board  at  Curd- 
worth  and  Minworth.  Here  large  areas  of 
rectangular  filters  have  been  constructed  over 
which  the  tank  liquor  is  distributed  by  means 
of  fixed  pipes  fitted  with  Bryan's  jets  (Fig.  3) 
as  supplied  by  Jones  &  Attwood,  Engineers,  of 
Stourbridge.  The  distributing  pipes  are  of 
3  in.  diameter,  spaced  9  ft.  apart,  and  carried 
by  cast-iron  chairs  on  the  surface  of  the 
clinker.  The  pipes  are  of  a  light  iron  hot 
water  weight  T^-  in.  thick,  with  bosses  for 
the  jets  cast  on  at  4  ft.  6  in.  centres.  These 


FIG.  3. — Bryan's  Fixed  Jets,  as  used  at 
Birmingham. 

bosses  carry  brass  sprinkler  jets.  The  head 
or  pressure  at  the  jet  is  about  7  ft.  6  in.,  giving 
a  discharge  of  400  gallons  per  square  yard 
per  day.  This  rate,  however,  is  reduced  by 
plugging  some  of  the  jets  or  by  regulating 
the  valve  on  the  main  supply  pipe.  In  some 
cases  there  is  an  arrangement  of  distributing 
pipes  and  sprinklers  suitable  for  working  with 
alternate  jets  (Fig.  4).  A  sprinkler  is  placed  in 
each  alternate  hole  and  the  intermediate  holes 
are  stopped  with  wood  plugs,  or  shut  off  by 
turning  the  centre  plug  in  the  adjustable  head 
form  of  the  jet.  The  dark  circles  represent 
the  distribution  when  working  one  set  of 
sprays,  and  the  light  circles  give  the  effect 
when  using  the  alternate  jets,  thus  securing 
good  and  uniform  distribution.  The  arrange- 
ment of  piping,  spacing,  &c.,  may  be  modified 


126 


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MUNICIPAL   AND    SANITAEY  ENGINEERING. 


DIS 


to  suit  any  shape  of  bed,  head  of  pressure 
available,  or  rate  of  distribution  required,  and 


this   limitation    does    not   obtain    and    other 
circumstances  are  favourable,  distribution  by 


4s?  VALVES      TO    WASHOUTS 


PIG.  4. — Diagram  of  Jones  &  Attwood's  Distributing  Pipes  and  Sprinklers. 


before  planning  a  system  of  piping  for  any 
given  scheme  of  beds,  the  safest  plan  is  to 
experiment  with  a  few  lengths  of  piping  and 
jets  under  the  actual  head  available  in  the 
permanent  works  so  as  to  accurately  arrive  at 
the  proper  spacing  of  pipes  required  and  the 
rate  of  discharge  per  square  yard  of  bed.  As 
the  liquid  descends  in  a  fine  spray  it  passes 
down  into  the  filter  and  induces  a  light  current 
of  air  to  follow,  thereby  maintaining  the 
aerobic  conditions  required  for  the  proper 
oxidation  of  the  sewage.  There  is  no  doubt 
that  the  fine  spraying  greatly  assists  the 
oxidation  of  the  liquid,  but  there  is  risk  of 
nuisance  from  smell  if  septic  sewage  is  used — 
a  danger  which  disappears  when  dealing  with 
average  domestic  sewage  treated  whilst  fresh. 
The  minimum  head  consumed  in  the  working 
of  the  jets  is  from  5  to  6  ft.  for  securing 
the  best  results,  a  consideration  which  may 
prohibit  the  use  of  this  system  in  situations 
where  the  available  fall  is  limited.  But  where 


this  means  has  many  advantages.  Under  suit- 
able conditions  it  is  economical  and  simple  in 
construction  as  compared  with  other  methods 


FIG.  o. — Arm  Jet  Sprinkler,  H.S.  Type,  Hinged 
Saddle  and  Clip,  with  Brass  Arm,  Cone,  and 
Nozzle. 

of  distribution,  requires  no  skilled  labour  in 
attendance,  possesses  no  working  or  moving 
parts,  and  where  the  sewage  undergoes 


127 


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proper  preliminary  preparation,  requires  but 
little    attendance     under    ordinary    working 
conditions.     In  addition  to  Birmingham,  this 
mode  of  distribution  is  used  by  the  Corpora- 
tions of  Tunbridge  Wells,  Darwen,  Carlisle, 
Crieff,  and  others.      Spraying  nozzles  were 
adopted    at    Birmingham,   after   careful 
comparison  of  various  methods,  as  being 
the  least  costly  system  of  distribution  for 
large  areas  of  niters.     There  is  practically 
no  reasonable  limit  to  the  size  or  shape 
of   beds  to  which   this  system   may  be 
applied,  but  there  is  a  certain  drawback 
in  the  necessity  of  workmen  walking  over 
the  surface  of  the  filter  to  attend  to  the 
jets.      The  "  Arm  jet  "  shown  in  Fig.  5 
is  the  most  effective  in  distribution,  and 
gives  no  trouble  as  regards  stoppage — 


type  of  distributor,  ingenious  application  has 
been  made  of  the  "  Barker's  Mill  "  principle. 
The  revolving  distributor  consists  of  a  number 
of  perforated  iron  pipes  radiating  from  a  central 
pillar  through  which  the  sewage  is  supplied. 
The  holes  in  the  distributing  pipes  being  all 

Candy  -  Whiff  a  Jeer 
Sfyr/'nJc/er 


FIG.  6. — Sewage  Spray  Nozzle,  adopted  at 
Columbus,  Ohio. 

this  latter  feature  being  a  great  advantage. 
A  solid  plug  of  sewage  water  issues 
through  the  "brass  nozzle  "  fixed  in  the 
distributing  pipe  and  impinges  upon  the 
"  brass  cone,"  held  in  any  desired  position 
by  an  adjustable  arm  so  as  to  regulate  the 
quantity  discharged  and  width  of  spread. 
These  jets  are  in  use  at  the  Birmingham 
sewage  works,  and  on  percolation  beds  at 
one  of  the  sewage  farms  of  the  Tunbridge 
Wells  Corporation.  A  "  jet  "  of  the  form 
shown  in  Fig.  6  has  been  adopted  at 
Columbus,  Ohio. 

The  rotary  and  travelling  systems  of  dis- 
tribution, whilst  overcoming  some  of  the 
drawbacks  attendant  upon  the  above-mentioned 
methods,  at  the  same  time  create  new  objections 
peculiar  to  these  systems.  With  a  view  of 
overcoming  the  difficulty  in  regard  to  the  pro- 
vision of  motive  power  for  driving  the  rotary 


FIG.  7.— Candy  Distributor. 

on  one  side  the  reaction  of  the  escaping  jets 
of  sewage  liquor  causes  the  pipes  to  revolve 
around  the  central  supporting  pillar  thus  dis- 
tributing the  liquid  over  the  circular  area 
commanded  by  the  length  of  the  arms  of  the 
distributor.  Much  care  is  required  in  properly 
apportioning  the  sizes  and  spacing  of  the 


128 


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MUNICIPAL  AND   SANITAEY  ENGINEERING. 


DIS 


discharge  holes  in  the  arms  in  order  to  secure 
uniform  distribution  over  the  whole  surface 
of  the  filters.  The  outer  ends  of  the  arms 
obviously  travel  over  a  much  greater  area 
than  those  parts  nearer  the  central  pillar, 
so  that  the  number  and  size  of  the  perforations 
must  be  proportionate  to  the  distance  from 
the  centre  in  order  to  secure  equity  of  dis- 
tribution as  far  as  possible.  The  difficulty  of 
uniformity  of  distribution  is  particularly 
marked  in  rotary  distributors  of  large  diameter 
as  the  rate  of  discharge  near  the  central  pillar 
differs  widely  from  that  at  the  outer  extremity, 
and,  in  order  to  meet  this  as  far  as  possible, 
the  perforations  near  the  centre  are  widely 
spaced,  whilst  those  at  the  outer  end  are  very 
close  together.  Another  attempt  to  meet  the 
same  difficulty  is  to  have  some  of  the  arms 
perforated  for  distribution  on  the  outer 
extremity  only  of  the  filter  with  a  lesser 
number  perforated  for  the  inner  or  central 
ring  only.  Even  with  these  adjustments 
some  portions  of  the  filter  will  be  sprinkled 
at  a  higher  rate  of  discharge  than  others. 
Another  point  requiring  careful  consideration 
arises  from  the  fact  that  the  sewage  is  ad- 
mitted through  the  fixed  pivot  at  the  centre  of 
the  filter,  and  difficulty  has  been  experienced 
in  providing  a  suitable  joint  between  this 
pivot  or  supply  pipe  and  the  arms  revolving 
around  it.  In  Adam's  "  Cresset "  distributor 
the  central  joint  or  coupling  is  a  simple  air- 
lock trap,  formed  by  the  locking  in  of  a  body 
of  air  between  the  outer  and  inner  annular 
spaces  of  the  lower  tank  and  the  body  of  the 
distributor  which  is  suspended  over  and  dips 
into  the  water  seal  below.  Thus  the  cylinders 
shown  revolve  in  water,  and  loss  by  friction  in 
the  centre  joint  is  reduced  to  a  minimum. 
The  illustration  also  shows  the  cross-head 
where  the  weight  of  the  distributor  is  mainly 
carried  by  independent  bearings  of  hardened 
steel  balls  running  in  steel  grooves.  These 
ball-bearings  and  races  may  be  removed  and 
replaced  without  dismantling  the  apparatus. 
The  distributor  is  well  balanced,  but  if  any 
settlement  should  occur  the  "  head"  may  be 
pushed  over  by  the  adjusting  screws,  thus 


avoiding  the  taking  down  and  re-setting  of 
the  distributor. 

A  simple  method  of  lifting  the  weight  of 
a  sewage  distributor  off  its  bearings  for  clean- 
ing or  repair  consists  in  the  provision  of  a 
vertical  screw  at  the  top  of  the  central 
standard.  Fig.  7  is  a  section  of  the  central 
pillar  of  the  "  Candy-Whittaker "  distributor 
of  the  Patent  Automatic  Sewage  Distributors, 
Ltd.,  London.  To  raise  the  weight  of  the 
distributor  clear  of  the  bearings  it  is  simply 
pushed  round  in  the  reverse  direction  to 
that  in  which  it  rotates  when  working,  when 
the  top  block  from  which  the  distributor  is 
suspended  raises  up  the  screw  and  so  clears 
the  bearings  accessible  for  repair,  cleansing, 
or  renewal.  The  ball-bearings  again  take 
the  weight  as  soon  as  the  distributor  is 
lowered  by  starting  to  revolve  in  its  ordinary 
working  direction.  Another  feature  of  this 
distributor  is  the  provision  of  a  "  mercury 
seal "  for  the  central  joint  which  is  quite 
water-tight  so  long  as  of  sufficient  depth.  A 
gun-metal  "check-ring"  is  also  provided  to 
prevent  the  forcing  out  and  loss  of  the  mercury 
through  any  sudden  increase  of  sewage  pres- 
sure beyond  the  weight  of  the  depth  of  seal 
provided.  A  "moisture-proof  oil  seal"  is 
arranged  at  the  top  of  the  central  pillar  for 
the  purpose  of  preserving  the  ball-bearings 
carrying  the  weight  of  the  distributor,  and  these 
bearings  again  are  run  in  an  oil  bath.  This 
distributor  is  very  extensively  used  by  a  great 
number  of  public  authorities,  and  the  results 
of  much  practical  experience  have  been  em- 
bodied in  its  design. 

In  the  circular  distributor  made  by  Geo. 
Jennings,  Ltd.,  the  centre  joint  is  above 
the  level  of  the  sewage  in  the  revolving  arms 
instead  of  below  as  in  the  previous  cases,  and 
the  sewage  is  discharged  from  the  central 
supply  pipe  into  an  annular  trough,  to  which 
the  distributing  arms  are  connected,  by  means 
of  siphons.  Farrer's  "Facile"  siphon  fed 
distributor  may  be  connected  direct  to  the 
septic  tank,  and  thus  works  with  a  minimum 
loss  of  head. 

The  construction  of  the  joint  with  the  central 


M.S.E. 


129 


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ENCYCLOPEDIA  OF 


BIS 


supply  pipe  in  the  circular  distributor  of  the 
Ames-Crosta  Sanitary  Engineering  Company 
is  shown  in  Fig.  8.  It  is  formed  of  two  gun- 
metal  rings  with  annular  grooves  and  projec- 
tions as  a  seal  against  the  escape  of  the  liquid. 
One  ring  is  fixed  to  the  supply  pipe  and  the 


FIG.  8. — Ames-Crosta  &  Co.,  Sectional 
Sprinkler  Pillar. 

other  to  the  revolving  distributor.  Between 
the  rings  is  placed  a  rubber  or  metal  dia- 
phragm. The  weight  of  the  distributor  is 
carried  on  ball  bearings  in  the  top  of  the 
centre  pillar,  which  are  readily  accessible  by 
means  of  a  raising  screw  for  lifting  the  dis- 
tributor off  its  bearings.  It  is  claimed  that 


the  distributor  will  work  with  so  small  a 
head  as  3  in.  Scott  Moncrieff's  circular 
power-driven  distributor,  erected  for  experi- 
mental purposes  at  Hanley,  produced  an 
excellent  effluent  owing  to  the  efficient  dis- 
tribution secured  by  its  means,  but  it  proved 
costly  to  maintain  and  was  replaced  by  a 
power-driven  distributor  of  a  lighter  design 
introduced  by  Hartley  &  Son,  of  Stoke-on- 
Trent. 

Hartley,  Causton,  &  Co.,  of  Stoke-on-Trent, 
have  introduced  a  power-driven  circular  sewage 
distributor  as  illustrated  in  Figs.  9,  10,  and  11, 
which  may  be  seen  in  use  at  the  Hanley 
sewage  works.  The  electric  motor  is  fixed 
at  the  end  of  the  distributor  as  shown,  and 
travels  on  a  rail  around  the  outside  wall  of 
the  bed :  the  arms  are  carried  at  the  centre 
on  ball-bearings.  The  sewage  flows  through 
a  stuffing-box  centre  tube  upwards  to  the 
balancing  arm  and  the  main  distributing  arm 
at  the  same  time.  The  sewage  is  distributed 
through  a  number  of  sectional  distributing 
tubes  arranged  in  echelon  to  facilitate  cleans- 
ing. The  horse-power  required  to  drive  the 
distributor  is  less  than  half-horse  power  per 
acre  of  bed,  and  the  apparatus  can  be  regu- 
lated to  increase  or  decrease  the  dose  of 
sewage  from  the  smallest  quantity  to  2,000,000 
gallons  per  acre  per  day.  Eotary  distributors 
are  also  made  by  Mather  &  Platt,  Ham,  Baker 
&  Co.,  and  others,  and  one  of  the  turbine 
ring-drive  type  is  manufactured  by  the  Septic 
Tank  Co.,  Ltd.  At  Worcester,  a  self-propelled 
Candy-Caink  sprinkler  (Fig.  12)  of  an  unusual 
type  is  in  use.  The  sewage  of  a  population  of 
50,000  persons  is  first  prepared  in  two  disin- 
tegrating tanks,  each  having  a  capacity  of  nine 
hours'  dry-weather  flow,  and  is  then  lifted  to  the 
filters  by  two  45  h.-p.  electric  motors  and  two 
90  h.-p.  gas  engines  fed  from  a  suction  gas 
plant.  The  tank  liquor  is  treated  on  six 
circular  percolating  filters,  each  of  200  ft. 
diameter,  upon  which  the  sewage  is  delivered 
by  means  of  Candy-Caink  distributors,  fitted 
with  Caink's  patent  jets.  These  filters  are  of 
washed  local  gravel  8  ft.  in  depth.  The 
storm  water  beds  can  also  be  used  as  straining 


130 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


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w 


131 


DIS 


DIS 


or  mechanical  filtration 
beds  for  removing  the 
fine  suspended  matter 
from  the  percolating  bed 
effluent,  and  there  are 
also  17  acres  of  land 
available.  The  sprinkler 
has  only  one  distributing 
arm  and  this  is  supported 
by  three  wheel  carriages 
running  on  three  con- 
centric tracks,  one  in  a 
small  well  at  the  centre, 
one  near  the  circumfer- 
ence of  the  bed,  and  one 
at  an  intermediate  posi- 
tion. The  distributor  is 
supplied  by  means  of  a 
siphon  from  a  stand-pipe 
at  the  centre  of  the  filter. 
The  siphons  from  all  the 
distributors  are  connected 
by  means  of  air  pipes 
carried  to  the  engine- 
room  where  they  connect 
with  a  vacuum  chamber, 
and  the  beds  are  thus 
readily  controlled  by 
opening  and  closing  the 
necessary  taps  or  valves 
in  the  engine-room  for 
the  purpose  of  starting 
the  siphon  feed  to  each 
bed  as  required.  The 
distributors  were  supplied 
by  the  Patent  Automatic 
Sewage  Distributors,  Ltd., 
of  Westminster. 

In  another  type  of 
rotary  distributor  for 
circular  beds  the  rotating 
arms  are  fitted  as  small 
water  wheels,  with  a 
number  of  buckets  or 
troughs  around  the  cir- 
cumference and  extending 
throughout  the  length  of 
the  arm.  The  apparatus 


132 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


DIS 


is  supplied  with  sewage,  by  means  of  a  feed  aerating  from  time  to  time.  The  water-wheel 
pipe  from  the  centre  of  the  filter  and  rotates  type  of  distributor  is  less  satisfactory  than 
upon  circular  rail  tracks  at  the  centre  and  the  rotary  and  fixed  spray  type  in  this  respect, 


FIG.  12. — Sewage  Distribution  at  Worcester  :  Self-propelled  Candy-Caink  Sprinkler. 


periphery  of  the  filter.  The  "  Fiddian " 
distributors  for  circular  filters  as  introduced 
by  Birch,  Killon,  &  Co.,  engineers,  Man- 
chester, are  of  this  type,  and  one  is  in- 
stalled at  Fazakerley  for  the  Liverpool 
Corporation. 

The  propelling  power  for  the  class  of 
distributor  shown  in  Fig.  13  is  also 
developed  on  the  principle  of  the  water 
wheel,  but  instead  of  taking  a  circular 
path  the  apparatus  travels  backwards  and 
forwards  over  filters  of  a  rectangular 
shape,  thus  securing  great  economy  of 
space  as  compared  to  the  circular  form  of 
bed. 

The  most  effective  method  of  applying 
sewage  to  bacteria  beds  is  in  the  form  of  a 
small  jet  or  fine  spray,  and  in  selecting 
a  distributor  it  should  not  be  one  of  the 
type  which  dashes  the  sewage  on  to  the 
bed  in  bucketfuls  so  as  to  cause  rapid  down- 
ward  flushes    through   the   bed.      The    dis- 
advantageous effect  of  this  is  minimised  by 
using  a  fine  top  layer  over  the  surface  of  the 


whilst  the  initial  cost  and  maintenance  is  also 
heavy.  Siphon ic  feeds  to  distributors  are 
oftentimes  troublesome  through  risk  of  "air- 
locking,"  and  the  introduction  of  mechanical 


FIG.  13. — Ham,  Baker's  Travelling  Distributors. 

joints  between  the  fixed  and  moving  parts  of 
such  apparatus,  as  by  means  of  an  ordinary 
stuffing-box  and  gland,  causes  much  friction 
and  resistance  to  the  rotary  movement  of  the 


bed,  but  this  will  usually  need  cleaning  and     distributor.     Efforts  have  also  been  made  to 


133 


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ENCYCLOPAEDIA  OF 


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develop  power  for  driving  distributors  by 
passing  the  sewage  through  a  turbine  inter- 
posed between  the  central  supply  pipe  and  the 
distributing  arms,  but  the  advantage  would 
appear  to  lie  with  the  "Barker's  mill" 
principle  inasmuch  as  the  reaction  of  a  jet 
issuing  from  the  distributor  arm  at  a  distance 
from  the  centre  of  rotation  must  be  more 
effective  than  a  similar  jet  escaping  close  to 
the  centre  and  with  a  very  short  leverage 
through  which  to  act. 

The  influence  of  the  wind  has  an  important 
effect  upon  the  working  of  moving  distributors 
propelled  by  a  small  head  only  of  sewage  liquor, 
and  in  some  cases  they  are  frequently  brought 
to  a  standstill,  thus  permitting  the  liquid  to 
pour  upon  the  filter  at  one  spot  and  stream 
through  the  bed  to  the  effluent  channel  in  an 
untreated  condition.  The  effects  of  continued 
severe  frost  and  snow  occasionally  derange 
the  working  of  distributors,  but  where  they 
can  be  kept  in  full  use  throughout  the  24 
hours  the  warmth  of  the  sewage  itself  is 
generally  sufficient  to  prevent  freezing.  If  the 
distributor  is  not  in  full  use  it  is  best  drained 
off  dry  to  avoid  bursting  of  pipes,  &c.,  should 
freezing  of  the  water  contained  therein  occur. 
The  distribution  of  the  sewage  by  all  existing 
forms  of  distributors  may  at  times  be  far  from 
perfect,  especially  where  only  a  limited  amount 
of  attention  is  given,  so  that  it  becomes  import- 
ant to  have  sufficient  depth  of  bed  to  distribute 
and  equalise  such  imperfections.  W.  H.  M. 

Dortmund  Settling   Tank.— This  is  a 

circular  conical-bottomed  precipitating  tank 
first  tried  at  Dortmund,  in  Germany,  by  Carl 
Kinebiihler,  and  afterwards  at  the  Chicago 
Exhibition.  The  sewage,  after  preliminary 
settling  in  an  ordinary  horizontal  tank,  passes 
down  a  vertical  central  downpipe  about  3  ft. 
6  in.  in  diameter,  to  a  depth  of  some  30  ft., 
where  the  sludge  settles  in  the  conical  shaped 
bottom.  Radial  arms  are  provided  at  the 
upper  end  of  the  conical  portion  of  the 
bottom  of  the  tank  for  the  purpose  of  dis- 
tributing the  sewage  evenly  throughout.  As 
it  consolidates  the  sludge  in  the  apex  of  the 


cone  is  pumped  out  by  a  6  in.  suction  pipe. 
This  type  of  tank,  like  others  which  are  off- 
shoots of  the  same  original  idea,  embodies  a 
good  principle  in  the  continuous  upward  flow 
of  the  sewage  with  a  downward  movement  of 
the  sludge,  but  in  practical  working  has  not 
given  the  satisfaction  first  contemplated  by 
many,  inasmuch  as  the  sludge  does  not  always 
gravitate  into  the  cone  but  floats  or  settles 
on  the  sides,  where  it  decomposes.  Colonies 
of  bacteria  also  form,  and  these  together  with 
the  putrid  sludge  pass  off  with  the  effluent. 
Matters  may,  however,  be  improved  by 
removing  the  sludge  daily,  by  adopting  a 
revolving  scraper  for  cleansing  the  internal 
surfaces  of  the  tank  walls,  and  by  having  the 
tanks  in  duplicate. 

Dosing  Tank. — The  name  "  dosing  tank  " 
is  applied  to  a  small  chamber  placed  between 
the  precipitating  or  settling  tanks  and  the 
contact  or  percolating  beds  for  the  purpose  of 
accumulating  a  sufficient  volume  of  liquid  for 
distribution  on  to  the  filters  in  cases  where 
the  flow  of  sewage  is  small  during  certain 
periods  of  the  24  hours.  Where  a  rotary 
distributor  is  used,  in  the  case  of  a  small 
works,  the  flow  may  fall  during  the  night  to 
such  an  extent  that  the  distributor  will  not 
revolve,  and  in  these  circumstances  the 
sewage  is  stored  in  a  "  dosing  tank  "  from 
which  it  is  discharged  in  bulk,  by  means  of  a 
siphon  or  other  suitable  contrivance,  on  to 
the  filter  beds,  which  are  thus  afforded  inter- 
mittent periods  of  rest. 

Drainage — Cast-iron. — Cast-iron  drain- 
age differs  from  ordinary  house  drainage  only 
as  regards  the  materials  of  which  the  under- 
ground drains  are  constructed.  It  has  many 
advantages  over  stoneware  drainage,  whereas 
only  one  drawback  may  fairly  be  urged  against 
it,  and  that  is  the  question  of  cost,  which  is 
about  30  %  more  than  that  of  stone-ware ; 
but  having  regard  to  the  security  obtained 
by  the  use  of  iron,  it  is,  doubtless,  the  most 
economical  material  in  the  long  run.  Apart 
from  having  a  longer  life  than  stone-ware 
drains,  in  itself  a  great  advantage,  cast-iron 


134 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


DRA 


drains  are  also  superior  in  other  respects.  In 
the  lirst  place  the  pipes  are  made  in  longer 
lengths,  there  being  a  joint  every  9  ft.  in  an 
iron  drain  as  against  every  2  ft.  in  a  stone- 
ware drain.  As  it  is  generally  accepted  that 
the  fewer  joints  there  are  in  a  drain,  the 


FIG.  1. 


fewer  chances  there  are  for  imperfections, 
the  advantages  of  iron  over  stoneware  would 
be  in  the  ratio  of  4^  to  1.  It  follows  from 
this  also  that  the  time  occupied  in  laying  a 
given  length  in  each  material,  and  conse- 
quently the  cost  of  labour,  is  distinctly  in 
favour  of  the  iron  drain.  Secondly,  the  joints 
of  iron  drains  can  be  made  in  all  weathers 
and  in  all  soils,  which  is  a  great  consideration 
in  the  case  of  drains  constructed  during  periods 
of  frost  or  rain  or  in  water-logged  ground — 
conditions  which  would  seriously  interfere 
with  the  making  of  stoneware  pipe  joints.  In 
the  third  place,  there  is  a  greater  likelihood  of 
a  stoneware  drain  giving  way,  owing  to  pres- 
sure, settlement  of  the  ground,  or  to  vibration, 
such  as  that  produced  by  an  underground 
railway  or  by  heavy  vehicular  traffic,  by  reason 
not  only  of  the  increased  number  of  joints  and 
correspondingly  increased  number  of  points 
of  possible  rupture,  but  also  because  of  the 
more  brittle  nature  of  the  materials  of  which 
both  the  pipes  and  the  joints  are  made.  In 
the  fourth  place,  iron  drains  may  be  laid  in 


a  variety  of  ways  which  would  be  impracticable 
in  the  case  of  stoneware  drains.  They  may 
be  fixed  openly  against  walls  or  suspended 
from  ceilings  (see  Fig.  1)  where  the  lowest 
floor  of  the  building  is  below  the  level 
of  the  public  sewer,  or  they  may  be  laid, 
subject  to  proper  fixing,  above  the  floor  of  a 
basement  or  in  a  culvert.  They  will  be  as 
safe  there  as  if  laid  underground,  and  possess 
the  advantage  that  every  portion  will  be  easily 
accessible  and  visible.  On  iron  piping  the 
manholes  may  be  made  on  the  piping  itself, 
as  shown  in  Fig.  2.  This  will  obviate  the 
necessity  for  constructing  air  and  water- 
tight brick  manholes.  A  further  advantage 
of  cast-iron  over  stoneware  drains  is  that 
the  former  do  not  require  continuous  con- 
crete foundations  except  in  cases  where  the 
ground  is  particularly  bad.  In  most  cases 
it  will  be  sufficient  to  provide  a  concrete  pier 
about  1  ft.  square  and  from  6  in.  to  12  in. 
deep  according  to  the  nature  of  the  ground 
under  each  socket.  All  cast-iron  pipes  used 
in  drainage  work  should  be  made  of  good 
tough  grey  iron  of  the  second  melting  run 
from  the  cupola.  The  pipes  should  be  cast 
with  sockets  downward  and  with  an  extra 
head  of  at  least  1  ft.  of  metal.  All  pipes 
above  4  in.  in  diameter  should  be  inclined 


FIG.  2. — Access  Pipe  or  Hatch  Box  on  Iron  Drain. 

at  an  angle  of  45°.  The  pipes  should  be 
straight,  true  in  section,  even  in  thickness  of 
metal,  perfectly  smooth  inside,  and  free  from 
air  and  sand  holes  and  other  defects.  Their 
sockets  must  be  strong,  deep,  and  sufficiently 
wide  all  round  to  leave  room  for  caulking  up 


135 


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ENCYCLOPEDIA  OF 


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the  joint ;  whilst  the  spigots  of  the  pipes  must 
be  provided  with  a  bead  on  the  end.  This 
bead  causes  the  spigot  of  one  pipe  to  lie  in  the 
socket  of  the  other  in  such  a  way  that  the 
pipes  are  concentric  when  joined.  The  bead 
will  also  ensure  an  equal  annular  space  all 
round  the  inside  of  the  socket,  and  help  to 
keep  the  lead  used  in  making  the  joint  from 
running  into  the  interior  of  the  pipes.  The 
walls  of  the  sockets  should  not  be  less  than  £  in. 
thicker  than  the  walls  of  the  pipes,  whilst  the 
internal  diameter  of  the  sockets  should  be 
from  £  in.  to  f  in.  larger  than  the  external 
diameter  of  the  pipes,  so  as  to  leave  a  suffi- 
ciently large  annular  space  all  round  the  pipes 
for  the  lead  joints.  The  pipes  must  be  capable 
of  withstanding  a  pressure  of  200  ft.  head  of 
water,  and  must  be  coated,  both  inside  and 
out,  by  some  anti-corrosive  solution,  such  as 
Dr.  Angus  Smith's  composition,  to  prevent 
deterioration  through  oxidation.  For  the 
proportions  and  weights  of  cast-iron  pipes  see 
article  "  CAST-IRON  PIPES." 

The  joints  of  iron  drains  should  be  made 
with  molten  lead  well  caulked  whilst  cooling. 

G.  J.  G.  J. 

Drainage,  House. — The  objects  to  be 
attained  in  carrying  out  a  perfect  system  of 
house  drainage  are  : — 1.  The  disconnection 
of  the  drains  from  the  public  sewer  or  other 
outfall.  2.  The  disconnection  of  the  rain 
and  waste-water  pipes  from  the  house  drains. 
3.  The  thorough  ventilation  of  the  whole 
drainage  system.  4.  The  entire  and  immedi- 
ate removal  of  all  matter  discharged  into 
the  drains.  5.  The  provision  of  means  of 
access  for  inspection,  testing,  and  cleansing  of 
the  drains.  6.  The  construction  of  the  entire 
system  in  such  a  manner  and  of  such  materials 
as  shall  preclude  the  possibility  of  leakage 
of  either  liquids  or  gases. 

1.  Of  these  requirements  the  first  is  attained 
by  breaking  direct  aerial  communication  be- 
tween the  drain  and  sewage  outfall  by  the 
insertion  of  a  ventilated  disconnecting  trap 
(see  article  "DISCONNECTING  TRAPS")  at  the 
outlet  end  of  the  drains.  For  convenience  of 


cleansing,  &c.,  this  trap  is  best  fixed  in  a 
manhole  ;  the  drain  or  drains  discharging  into 
it  terminating  in  an  open  channel  running 
into  the  trap.  This  disconnection  is  desirable 
for  the  protection  of  the  house  drains  against 
infection  from  sewers,  be  that  infection  merely 
one  of  fouled  air,  of  dangerous  gases,  or  of 
germs  of  disease. 

2.  Secondary  disconnection  is   effected  by 
breaking   the  direct  communication  between 
waste-water    and    rain-water   pipes   and   the 
drains  by  the  use  of  gully  traps.     These  are 
placed  at  the  heads  or  inlets  of  all  drains  that 
do  not  take  water  closets  or  soil  pipes,  and 
serve  to  shut  out  from  the  waste  and  rain- 
water pipes,  all  vitiated  air  generated  in  the 
house   drains   themselves.      The   pipes   may 
be  discharged  over  or  beneath  the  gratings  of 
the  gullies,  but  must  in  all  cases  have  their 
open  ends  above  the  level  of  the  water  standing 
in  the  traps,  which  latter  must  be  fixed  in  the 
open    air.      It   occasionally   happens   that  a 
waste  pipe  or  rain-water  pipe  must  of  necessity 
pass  down  in  the  interior  of  the  house.     In 
such    a   case   it  should    be    continued  below 
ground  in  a  horizontal  position  (at  a  proper 
fall)  to  the  exterior,  and  there  discharged  over 
a    gully.      Should   this    arrangement    prove 
impracticable,  the  gully  may  be  fixed  within 
the  building,  but  as  there  is  a  chance  of  its 
water-seal   evaporating   and  consequently  of 
foul  air  being  liberated,  the  gully  must   be 
hermetically  sealed  at  the  ground  level  and 
the   waste   pipe   provided   with   an   air  inlet 
opening  terminating  in  the  open  air. 

3.  The  third  object  named  as  being  neces- 
sary to  ensure  a  sanitary  system  of  drainage 
is    ventilation.      This    is    essential    in    the 
first    place   to   secure   proper   disconnection, 
and    secondly,   for   the    oxygenation    of   the 
interior  of  the  drains  or  pipes,  and  for  the 
dissemination  of  such  gaseous  products  as  may 
be  generated  in  the  drains   or  waste  pipes. 
For  proper  ventilation  there  should  be  both 
inlets  for  fresh  air  and  outlets  for  vitiated  air. 
Moreover,  if  ventilation  is  to  be  complete,  the 
inlets  and  outlets  must  be,  as  far  as  practic- 
able,   at  the  extreme    opposite  ends    of  the 


136 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


DRA 


drains  or  pipes  to  be  ventilated.  It  is,  more- 
over, necessary  that  the  inlets  and  outlets 
should  be  at  appreciably  different  levels,  since 
there  will  otherwise  be  a  tendency  to  equili- 
brium due  to  the  collection  of  the  heavier 
gases,  such  as  carbonic  acid  gas,  at  the 
lowest  points  of  the  drains,  &c.  Soil  pipes, 
having  in  any  case  to  be  carried  up  above 
the  roof  of  the  building  upon  which  they  are 
fixed,  provide  convenient  and  inexpensive 
up-cast  ventilation  shafts,  and  are,  therefore, 
usually  made  use  of  for  the  purpose.  If  it  is 
possible  to  so  arrange  the  soil  pipes  that  they 
may  ventilate  the  whole  drainage  system,  no 
other  up-cast  shafts  will  be  necessary.  Taking 
the  case  of  a  small  house,  or  of  an  ordinary 
town  house,  for  instance,  if  the  soil  pipe  is 
at  the  head  of  the  drain,  through- ventilation 
is  attained  by  the  provision  of  an  air-inlet  at 
the  opposite  end  of  the  system.  In  cases 
where  the  soil  pipe  is  centrally  placed  a 
second  up-cast  shaft  will  be  necessaiy  at  the 
head  of  the  drain,  or  alternatively  an  air-inlet 
at  each  extremity  of  the  system.  This  latter 
method  is  not  permitted  by  the  by-laws  of 
many  towns.  In  other  cases,  wiiere  one  or 
more  long  branch  drains  exist,  the  head  of 
each  must  be  provided  with  a  ventilation 
shaft.  This  arrangement,  however,  involves 
the  splitting  up  of  the  air-current  drawn 
through  the  inlet,  and  tends  to  produce 
inefficient  ventilation  as  the  air  usually  travels 
through  the  path  of  least  resistance,  and 
possibly  would  only  occasionally  reach  some 
of  the  outlet  shafts  under  favourable  circum- 
stances. It  is  desirable,  therefore,  in  an 
extensive  drainage  scheme,  to  subdivide  the 
system  by  judicious  trapping  and  to  provide 
a  separate  air-inlet  to  each  section.  Short 
branch  drains  require  no  special  provision  for 
ventilation,  as  the  flow  through  them  will  as 
a  rule  suffice  to  displace  the  air  contained 
therein  and  so  bring  it  under  the  influence  of 
the  air-currents  in  the  main  drains.  Ventila- 
tion shafts,  other  than  soil  pipes,  should  not 
be  less  than  4  in.  in  diameter,  and  should 
preferably  be  constructed  of  lead  piping. 
Cast-iron  pipes,  although  frequently  used, 


being  cheaper,  are  not  desirable,  as  they  are 
acted  upon  by  gases  occasionally  present  in 
drains  and  also  rapidly  deteriorate  by  rusting. 
Soil  pipes  should  not  be  less  than  3|  in.  in 
diameter,  nor  more  than  4  in.,  and  may  be 
made  of  drawn  lead  piping  of  not  less  than 
8  Ibs.  to  the  superficial  foot,  or  of  heavy  cast- 
iron  piping.  In  the  case  of  soil  pipes  washed 
by  sewage,  the  iron  is  protected  from  deteriora- 
tion by  the  slimy  film  which  soon  forms  on 
their  interior.  That  portion  of  the  pipe  which 
lies  above  the  highest  closet  and  receives  no 
sewage  should,  however,  be  of  lead  in  all 
cases.  All  outlet  ventilation  pipes  should  be 
carried  up  full  bore,  above  the  roof,  and 
terminated  well  out  of  the  way  of  windows 
and  chimneys.  Their  openings  should  be 
protected  against  blockage  by  domical  copper 
wire  guards.  Cowls  are  not  necessary,  nor 
advisable,  as  they  frequently  only  serve  as 
shelters  for  birds'  nests.  Inlet  ventilation 
pipes  should  be  arranged  to  have  their 
openings  in  positions  where  they  are  not 
liable  to  cause  annoyance  should  there  be 
a  back-draught  from  the  drains.  They  may 
then  be  simply  protected  by  open  gratings. 
The  mica  flap  valves  frequently  made  use  of 
for  shutting  off  occasional  back  currents  from 
the  drains  are  not  desirable  fittings,  as  they 
are  very  liable  1o  get  out  of  order,  and, 
either  to  leave  the  inlets  open  at  all  times 
or  to  permanently  close  them.  The  proper 
ventilation  of  waste  pipes,  by  which  is  under- 
stood the  discharge  pipes  of  sinks,  baths,  and 
lavatories,  is  important,  not  only  to  prevent 
them  from  becoming  foul,  but  also  because 
the  traps  of  fittings  discharging  into  them  are 
liable  to  lose  their  "  seal,"  should  the  waste 
pipes  be  unventilated  (see  "  SIPHONAGE  ").  The 
not  unusual  practice  of  constructing  waste 
pipes  with  hopper  heads,  into  which  the  dis- 
charges of  various  fittings  are  collected,  is 
not  desirable,  because  if  ventilated  near 
windows  considerable  nuisance  arises.  The 
pipes  should  be  continued  up  to  above  the 
eaves  of  the  roof  for  ventilation  in  a  similar 
manner  as  soil  pipes,  and  the  branches  from 
the  fittings  connected  to  the  main  stack  pipe. 


137 


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ENCYCLOPAEDIA   OF 


DRA 


This,  of  course,  is  only  necessary  in  the  case 
of  waste  pipes  from  fittings  fixed  upon  the 
upper  floors.  Short  waste  pipes  from  fittings 
on  the  lowest  floor  are  sufficiently  well  venti- 
lated by  the  provision  of  "  puff"  pipes  carried 
to  the  exterior.  Where  a  number  of  fittings 
discharge  into  a  stack  pipe  common  to  all,  the 
trap  of  each  fitting,  other  than  the  highest 
one  on  the  stack,  must  be  further  ventilated 
by  an  anti-siphonage  pipe,  which  may  be 
branched  into  a  main  ventilation  pipe  taking 
them  all  and  carried  up  to  the  eaves  inde- 
pendently (as  shown  in  the  illustration  under 
the  article  "  SIPHONAGE  "),  or  branched  into 
the  ventilation  pipe  from  the  waste  pipe  above 
the  level  of  the  highest  fitting  on  the  stack. 
This  applies  also  to  the  traps  of  water-closets 
where  a  number  of  these  fittings  discharge 
into  one  soil  pipe. 

4.  The  immediate  removal  of  the  sewage 
discharged  into  the  drains  is  dependent  upon 
proper  gradients,  suitable  dimensions,  and 
efficient  flushing  arrangements.  In  size,  the 
drains  should  be  as  small  as  practicable, 
as  this  will  tend  to  cleanliness  and  a  rapid 
discharge.  Thus  a  flow  of  sewage  which  will 
cause  a  4-in.  drain  to  run  full  and  to  be 
self-cleansing  on  account  of  the  thorough 
flush  which  it  receives,  will  not  even  half  fill 
a  6-in.  drain  ;  while  a  9-in.  drain  would 
only  run  about  one-quarter  full.  As  the 
mean  velocity  of  sewage  flowing  through  a 
drain  varies  directly  (up  to  a  certain  point),  as 
the  depth  of  the  flow  of  sewage,  the  drain  in 
which  the  sewage  flows  deepest  (i.e.,  the 
smallest  drain)  will  have  the  greatest  scouring 
and  cleansing  flow.  Moreover,  in  an  un- 
necessarily large  drain,  which  is  never  properly 
flushed,  there  is  room  for  splashing  and  for  the 
deposit  of  sewage  matter,  a  condition  of  things 
which  is  opposed  to  true  sanitation.  In  design- 
ing a  system  of  drainage  the  probable  flow  of 
sewage  should  be  carefully  calculated,  as  also 
should  the  possible  amount  of  rain-water  to  be 
removed.  Should  a  small  drain,  say  a  4-in., 
be  found  insufficient  to  take  the  whole  flow,  it 
wiH  be  desirable  to  provide  a  small  drain  for 
the  sewage  proper  and  a  certain  amount  of 


the  rainfall,  and  to  lay  a  second  drain  for  the 
removal  of  the  remaining  rain-water.  This 
course  is  preferable  to  the  laying  of  a  large 
drain  which  would  only  be  thoroughly  cleansed 
during  periods  of  heavy  rains.  No  less  im- 
portant than  their  sizes  are  the  gradients  of 
the  drains.  It  should  be  borne  in  mind  that 
even  the  smallest  drain  (which  in  practice 
should  not  be  less  than  4  in.  in  diameter) 
will  only  run  full,  or  nearly  so,  under 
exceptional  circumstances.  During  dry 
weather,  for  instance,  the  flow  through  the 
drains  will  consist  merely  of  excrementitious 
matter  and  waste  water,  the  bulk  of  which 
will  be  delivered  into  the  drains  spasmodically 
through  waste  pipes  considerably  smaller 
than  the  drains.  It  is,  therefore,  necessary 
in  laying  a  drain  not  only  to  make  use  of 
small  piping,  but  also  to  lay  it  at  gradients 
which  will  provide  it  with  a  self-cleansing 
flow,  that  is,  with  a  flow  sufficiently  deep  to 
float  fffical  matter  to  the  outlet.  In  an 
excessively  flat  drain  the  flow  of  sewage  will 
be  so  sluggish  as  to  permit  the  deposit  of  the 
heavier  portions  of  the  sewage.  In  an 
excessively  steep  drain,  on  the  other  hand,  the 
depth  of  the  flow  may  be  so  small  as  to  be 
insufficient  to  float  the  larger  particles  of 
sewage  to  the  outlet  of  the  drain.  Both 
extremes  must,  therefore,  be  avoided.  The 
most  suitable  falls  for  drains  are  those  which 
will  impart  to  the  sewage  a  velocity  of 
3  ft.  per  second  when  the  drain  is  flowing 
quarter  full,  or,  what  is  equivalent  thereto, 
a  velocity  of  4  to  5  ft.  per  second  when 
flowing  full  or  half  full.  These  falls  are 
roughly  :— 


For  a  4  in.  drain 

5  in.      „ 
„  .     6  in.      „ 
9  in. 


1  in  40. 


50. 
60. 
90. 


These  gradients  should,  as  far  as  possible,  be 
adhered  to  in  all  cases.  Where  the  fall 
available  is  not  sufficient  to  give  these  gradients 
throughout  the  system,  the  branches  should  be 


138 


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MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


DRA 


so  laid  and  the  main  drain  given  a  somewhat 
smaller  rate  of  fall  and  provided  with  means  of 
flushing,  rather  than  sacrifice  the  self-cleansing 
gradients  of  the  branches,  which  cannot  be 
coveniently  flushed  individually.  As  already 
stated  it  is  only  occasionally  that  any  con- 
siderable volume  of  sewage  is  discharged 
through  a  house-drain  at  one  time.  During 
the  periods  of  minimum  flow,  therefore,  even 
the  best  of  drains  will  be  far  from  self-cleansing, 
and  it  is  therefore  desirable  that  all  drains 
should  be  periodically  and  efficiently  flushed. 
Automatic  flushing  is  of  the  greatest  assistance, 
not  only  in  keeping  a  drain  free  from  deposit, 
but  also  for  the  removal  of  grease,  and  should 
be  made  use  of  whenever  possible.  The  great 
point  in  drain  flushing  is  to  discharge  the 
available  water,  periodically,  automatically, 
and  in  suitable  quantities,  at  a  rate  of,  say, 
from  2  to  4  gallons  per  second.  For  this 
purpose  appropriate  apparatus  (see  "  FLUSHING 
TANKS")  are  necessary  in  order  that  the  water 
may  be  collected  and  retained  until  the  desired 
quantity  has  accumulated,  and  then  suddenly 
discharged  into  the  drains.  Under  such  a 
system  on  the  one  hand,  the  merest  dribble  of 
water  may  be  made  use  of,  while  on  the 
other  40  or  50  gallons  of  water  may  be 
made  more  efficient  than  1,000  gallons 
discharged  in  a  small  continuous  stream. 
Flushing  tanks  should  be  fixed  at  the  head  of 
the  main  drain  where  the  drainage  system  is 
a  small  one,  and  at  the  head  of  each  of  the 
most  important  branch  drains  where  the 
system  is  extensive.  If  possible,  it  should  be 
arranged  that  one  tank  discharges  into  the 
drain  taking  the  flow  from  the  scullery  sink, 
as  this  is  frequently  highly  charged  with 
grease.  The  discharge  pipes  of  the  tanks  may 
be  connected  to  the  drains  through  back  inlets 
or  ordinary  gullies,  or  they  may  be  attached 
to  the  arms  of  flushing  rim  'gullies,  that  is 
gullies  provided  with  flushing  rims  and  made 
specially  for  the  purpose.  The  capacities  of 
the  tanks  must  necessarily  depend  upon  the 
diameters,  lengths,  and  gradients  of  the  drains 
upon  which  they  are  provided.  Broadly 
speaking  it  will  be  found  that  the  following 


volumes     of     water     will     give     satisfactory 
results : — 


For  a  4  in.  drain 

K 

?>    »>  "  >i        » 


.  30  to  40  gallons. 
.  40  „  60       „ 
.  60       100 


5.  As  a  broad  principle,  every  pipe  and 
connection  comprised  by  the  drainage  system 
should  be  made  accessible  throughout,  for  the 
purpose  of  enabling  stoppages  to  be  located 
and  removed  without  loss  of  time  and  without 
damage  to  the  component  parts  of  the  system. 
It  permits  also  of  the  inspection,  cleansing  and 
testing  of  the  drainage  system,  enables  leak- 
ages to  be  located  and  rectified  without  un- 
necessary laying  bare  of  drains,  and  therefore 
brings  all  that  would  otherwise  be  out  of  sight 
and  out  of  reach  under  perfect  control.  In 
vertical  piping  such  as  soil  pipes,  waste  pipes, 
and  pipes  above  ground  generally,  means  of 
access  are  provided  in  the  case  of  iron  pipes  by 
the  use  of  suitable  access  pipes  made  for  the 
purpose.  They  consist  of  pipes,  straight  or 
bent,  fitted  with  removable  lids  which  are 
capable  of  being  closed  air-tightly.  (See 
"  ACCESS  PIPE.")  In  lead  pipes  access  is 
provided  for  by  the  insertion  on  the  pipes  of 
screwed  brass  caps  and  sockets.  These  open- 
ings into  the  pipes  must  be  suitably  placed  so 
that  the  fullest  advantage  may  be  derived 
from  them  both  for  the  removal  of  accumula- 
tions, where  such  are  liable  to  take  place,  and 
for  the  insertion  of  a  cane  or  brush  for  clean- 
ing purposes  whenever  that  should  become 
necessary.  In  underground  piping,  that  is  in 
the  drains  proper,  access  is  provided  by  means 
of  manholes  which  should  be  placed  at  all 
important  changes  of  direction,  and  also  on 
straight  lengths  of  drain  wherever  these 
are  considerable.  All  branch  drains  should 
be  arranged  to  join  the  main  drains  in  these 
manholes,  and  the  drains  to  or  from  them 
laid  in  perfectly  straight  lines  from  point  to 
point.  Manholes  should  be  constructed  of 
brickwork  in  cement  upon  proper  cement 
concrete  foundations,  and  should  be  made 
perfectly  water-tight  up  to  the  ground 


139 


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ENCYCLOPEDIA  OF 


DRA 


level.  This  is  arrived  at  by  rendering  the 
surfaces  of  the  manholes  with  cement  or  by 
lining  them  with  slabs  of  plate  glass.  Man- 
holes constructed  of  glazed  bricks  are  not 
desirable,  because,  although  capable  of  being 
made  water-tight,  the  joints  of  the  brickwork 
favour  the  accumulation  of  dirt.  The  man- 
holes, which  should  be  situated  in  the  open, 
must  be  covered  at  the  ground  level  with  air- 
tight iron  covers  and  frames.  Should  a  man- 
hole of  necessity  have  to  be  placed  within  a 
building,  a  double  cover,  capable  of  sealing 
itself  by  the  condensation  arising  from  the 
drains,  must  be  provided,  or  other  means 
adopted  to  ensure  that  the  covers  shall  be 
permanently  air-tight.  Through  these  man- 
holes all  drains  should  pass  in  the  form  of 
open  channels  shaped  out  of  concrete  and 
rendered  in  cement,  or  properly  shaped  glazed 
stoneware  channels  set  in  cement.  It  is 
desirable  that  the  branch  channels  should  be 
at  a  slightly  higher  level  than  the  main 
channel  into  which  they  deliver.  The  branch 
channels  should,  further,  invariably  discharge 
in  the  direction  of  the  outlet  of  the  manhole 
and  should  be  so  placed  that  the  discharge  of 
one  does  not  enter  any  of  the  channels  on  the 
opposite  side  of  the  manhole.  The  most  con- 
venient proportions  for  ordinary  manholes 
are  :— 

For  manholes  1  ft.  6  in.  or  less   in  depth — 

2  ft.  by  2  ft. 

,,  ,,         between  1  ft.  6  in.  and  2  ft.  6  in. 

in    depth — 2    ft.    6   in.    by 

2  ft. 

,,  ,,         above   2    ft.  6  in.    in   depth — 

3  ft.  6  in.  by  2  ft.  6  in. 

When  over  7  ft.  6  in.  in  depth  the  upper 
portion  of  the  manhole  may  be  contracted  in 
size  by  constructing  an  arch  at  a  height  of 
5  ft.  above  the  invert  of  the  drain  ;  a  shaft 
2  ft.  by  2  ft.  in  the  interior  being  carried  up 
to  the  level  of  the  ground.  The  construction 
of  an  ordinary  manhole  is  shown  on  page  77. 
6.  Construction.  —  Upon  this  is  depen- 
dent, more  than  upon  anything  else,  the 
health  and  well-being  of  the  inmates  of  the 


house  in  connection  with  which  the  drainage 
system  has  been  provided.  The  entire  system 
must  be  water-tight  to  prevent  the  pollution 
by  sewage  of  the  subsoil  and  foundations, 
and  in  many  cases  also  the  pollution  of  the 
water-supply  to  the  house  or  other  buildings 
in  the  vicinity.  It  must  also  be  air-tight 
to  preclude  the  possibility  of  polluting  the  air. 
The  materials  made  use  of  in  drainage  con- 
struction are  cast-iron  and  stoneware.  For 
the  former,  which  has  many  advantages,  see 
article  "  DRAINAGE,  CAST-IRON."  In  the 
case  of  stoneware  pipes,  only  those  of  best 
quality  should  be  made  use  of.  Earthenware 
or  fireclay  pipes  must  be  avoided  entirely,  as 
they  are  usually  absorbent  and  are  not  as 
tenacious  and  strong  as  stoneware  piping. 
Nor  are  they,  as  a  rule,  burnt  at  a  sufficiently 
high  temperature  to  become  vitrified.  The 
stoneware  pipes  used  should  be  salt-glazed, 
highly  vitrified,  perfectly  smooth  inside, 
straight,  true  in  section,  even  in  thickness, 
free  from  sandholes,  cracks,  and  other  defects, 
and  should  be  provided  with  strong  deep 
sockets  so  as  to  allow  of  proper  joints  being 
made  (see  "  STONEWARE  PIPE  JOINTS  ").  They 
should  be  tested  to  a  pressure  of  from  20  ft. 
to  25  ft.  head  of  water.  Stoneware  pipe 
drains  should  in  all  cases  be  laid  upon  a 
continuous  cement  concrete  bed  at  least 
6  in.  thick,  and  in  width  sufficient  to  pro- 
ject on  each  side  of  the  drain  a  distance  at 
least  equal  to  the  external  diameter  of  the 
drain.  After  being  tested  and  found  per- 
fectly water-tight,  concrete  should  be  filled 
in  on  each  side  of  the  drain  so  as  to  pre- 
clude the  possibility  of  lateral  movement. 
Where  a  stoneware  drain  passes  under  build- 
ings or  roads  or  in  other  similar  positions, 
it  should  be  entirely  surrounded  by  concrete 
to  a  thickness  of  at  least  6  in.  In  each 
case  where  the  drain  passes  under  a  wall  a 
relieving  arch  should  be  built  over  it  so  that 
there  may  be  no  pressure  on  the  drain.  Soil- 
pipes  may  be  constructed  of  iron  or  of  lead. 
In  the  case  of  the  former  the  piping  should  be 
of  at  least  "medium"  strength  (see  "  PIPES, 
WEIGHTS  AND  DIMENSIONS  OF  CAST-IRON  ")  and 


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BUS 


the  joints  made  with  molten  lead  well  caulked. 
Lead  piping  should  be  hydraulic  drawn  and 
at  least  8  Ibs.  weight  to  the  superficial  foot. 
Where  the  pipe  has  unavoidably  to  be  fixed 
inside  a  building,  piping  of  10  Ibs.  strength 
should  be  made  use  of.  In  either  case  the 
joints  should  invariably  be  of  "  wiped  "  lead. 
Ventilation  pipes  should,  as  already  stated, 
always  be  constructed  of  lead.  Hydraulic 
drawn  lead  piping  is  also  the  material  to  be 
used  for  all  waste  pipes,  and  the  joints  in  this 
case  should  also  be  of  "wiped"  solder,  except 
where  the  pipes  are  of  some  length  and 
intended  to  take  hot  water.  Under  these 
circumstances  "expansion  joints"  are  per- 
missible in  order  to  allow  free  movement  to 
the  pipes  when  under  the  influence  of  expan- 
sion and  contraction,  which  would  otherwise 
soon  cause  them  to  break.  Rain-water  pipes 
should  be  of  galvanized  iron — the  ordinary 
painted  rain-water  pipe  being  liable  to  choke 
from  internal  rust.  The  joints  of  these  pipes 
should  be  made  with  red  lead  putty.  On  com- 
pletion of  the  drainage  system,  each  and  every 
component  part  should  be  subjected  to  thorough 
tests,  as  to  which  see  article  "  DRAIN-TESTING." 
It  is  also  desirable  that  all  drainage  systems 
should  be  tested  periodically,  so  that  defects 
may  be  discovered  and  remedied  before  they 
reach  a  serious  stage.  (See  "PLUMBING.") 

G.  J.  G.  J. 


Dry     Earth     System.— (See 

CLOSETS.") 


EARTH- 


"Dry -weather   flow"    of    Sewage.— 

This  phrase  means  the  ordinary  daily  average 
quantity  of  true  sewage  from,  any  given 
population,  free  from  augmentation  by 
rainfall  and  subsoil  soakage.  The  quantity 
should  therefore  approximate  closely  to  the 
amount  of  the  water-supply  to  the  same 
population,  and,  in  a  well  sewered  district, 
commonly  amounts  to  from  25  to  30  gallons 
per  head  of  the  population,  but  "trade 


wastes  "  and  special  local  conditions  may  alter 
this  amount  in  certain  cases. 

Ducat's  Filter. — This  is  an  aerating 
filter  for  sewage  treatment  constructed  with 
external  walls  of  3  in.  drain  pipes,  laid  with 
the  outer  ends  3  in.  higher  than  the  inner  to 
prevent  sewage  leaking  outwards.  Aerating 
layers  of  drain  pipes  are  placed  at  intervals 
throughout  the  depth  of  the  filtering  material, 
which  latter  consists  of  £  in.  to  \  in.  vitrified 
clinker.  The  object  aimed  at  is  that  air 
should  continually  pass  laterally  through  the 
filter  with  a  view  of  keeping  the  same  regularly 
at  work  without  intermission.  Another  feature 
is  that  crude  sewage  is  claimed  to  be  dealt 
with,  but  experience  teaches  that  under  nearly 
all  circumstances  some  form  of  preliminary 
preparation  such  as  screening  and  settlement 
of  the  raw  sewage  is  needed.  The  direct 
oxidation  of  the  sewage  by  currents  of  air 
produces  considerable  cooling ;  the  system 
therefore  requires  to  be  supplemented  by  hot- 
water  pipes  fed  by  a  boiler  situate  in  a  heating 
chamber  adjoining.  The  Ducat  system  has 
been  experimented  with  at  Leeds,  Market 
Drayton,  Hendon,  Button,  and  also  at  the 
Tattingstone  Workhouse,  near  Ipswich. 

Dundrum  Settling  Tanks. — Mr.  Kaye 
Perry  has  used  tanks  to  which  this  name  is 
applied.  The  tanks  are  three  in  number  each 
7  ft.  square  by  16  ft.  deep,  and  containing 
5,000  gallons  of  sewage  each.  The  liquid 
enters  near  the  bottom  to  each  tank  in 
succession,  and  by  the  upward  flow  principle 
of  the  Dortmund  and  other  tanks  the  heavier 
suspended  matters  are  left  behind. 

Dust  Bins. — Receptacles  provided  in  con- 
nection with  dwellings  for  the  collection  of 
ashes  and  other  house  refuse.  These  bins 
should  only  be  used  for  dry  refuse ;  cabbage 
leaves,  food  scraps,  paper  and  similar  material 
liable  to  decomposition  being  better  disposed 
of  by  burning,  in  which'  householders  should 
be  encouraged.  Dust  bins  frequently  consist 


141 


BUS 


ENCYCLOPEDIA  OF 


BUS 


of  a  brick  or  wooden  pit  from  which  the 
refuse  is  shovelled  out  when  about  to  be 
removed.  This  involves  much  dust  and 
nuisance  and  must  be  considered  insanitary. 
Better  bins  are  those  generally  known  as 
"sanitary,"  which  are  made  of  galvanized 
iron  and  are  provided  with  a  light-fitting  lid 
to  exclude  rain,  as  moisture  favours  decom- 
position. These  bins  may  be  bodily  removed 
for  emptying.  Preference  should  be  given  to 
those  that  are  round  in  shape  or  have  rounded 
corners,  as  being  more  readily  cleaned. 
Another  form  of  sanitary  bin,  much  used 
in  the  North  of  England,  is  one  made  of 
metal  and  hinged  in  an  aperture  in  a  boundary 
wall  in  such  a  way  that  ashes  may  be  thrown 
in  from  the  house  side  of  the  wall,  while  the 
emptying  may  take  place  from  a  passage  at 
the  back  of  the  wall  by  simply  tipping  over 
the  bin. 

Dust  Prevention. — Surfacing  Roads — Oiled 
Roads — Dust  Palliatives — Apparatus. — The  dust 
problem  is  a  very  ancient  one,  but  has  only 
assumed  an  acute  form  since  the  advent 
of  motor  traffic.  Dust  has  a  deprecating 
effect  upon  everything  with  which  it  comes 
in  contact,  and  is  a  source  of  great  danger  to 
the  public  health.  It  not  only  predisposes 
to  diseases  of  the  lungs,  but  as  a  carrier  of 
disease  germs  is  a  greater  source  of  danger 
than  mud.  To  permanently  cure  the  evil 
would  involve  greater  expense  than  our  local 
bodies  are  prepared  to  involve  themselves  in. 
Moreover  the  vast  number  of  roads  which 
have  been  formed  of  macadam  only  allow  of 
certain  palliative  measures  being  adopted. 
Many  engineers  suggest  a  system  of  roads  in 
duplicate,  one  for  heavy  and  the  other  for 
light  traffic,  each  road  surface  being  made  of 
materials  suitable  to  withstand  the  strain  set 
up  by  passing  vehicles.  This  system  is,  how- 
ever, prohibitive  on  the  ground  of  its  great 
expense. 

Before  treating  of  palliatives  for  existing 
surfaces,  we  will  deal  with  systems  that  have 
been  generally  adopted  for  the  prevention  of 
dust  in  making  new  roads. 


Many  systems  have  been  employed,  among 
them  being  wood-paving,  tarred  macadam, 
and  many  patent  systems  of  binders, 
asphalte,  &c. 

In  every  case  success  largely  depends  on 
the  foundation  of  the  road,  and  the  reader  is 
referred  to  the  article  on  "  ROADS,  STREETS, 
AND  PAVEMENTS  "  for  further  consideration 
of  this  point.  It  will  be  well  to  point  out 
that  only  the  best  materials  should  be  used 
and  the  work  carried  out  in  the  best  possible 
manner. 

SYSTEMS  OF  SURFACING  ROADS. — WOOD-PAV- 
ING.— This  has  undoubtedly  decreased  the 
dust  in  main  thoroughfares,  though  much 
still  arises  from  horse  droppings,  &c.,  but  if 
properly  ordered  as  pointed  out  in  the  article 
on  "  STREET  CLEANSING,"  part  of  the  dust  may 
be  speedily  removed. 

TAR  MACADAM. — This  method  of  surfacing 
roads  for  dust  prevention  has  been  largely 
adopted  with  varying  results.  The  materials 
used  are  generally  limestone  or  ironstone 
slag,  the  latter  being  stronger  than  limestone. 
Care  must  be  exercised  over  the  tar,  as  upon 
it  depends  very  largely  the  success  of  the 
surface.  In  hot  weather  owing  to  bad  tar 
or  unsuitable  stone  being  used,  or  defective 
mixing  of  the  materials,  the  surface  becomes 
sticky  and  dangerous.  There  is  little  doubt 
that  the  best  way  of  drying  the  stone 
is  by  placing  it  in  specially  heated  ovens, 
the  stone  being  turned  over  at  intervals 
to  ensure  it  being  thoroughly  dried  and 
heated.  The  tar  should  in  all  cases  be  boiled, 
and  if  it  is  of  poor  quality  a  little  pitch  will 
improve  it.  The  mixing  of  the  tar  and 
the  stone  requires  very  careful  attention. 
Engineers  have  different  methods  of  mixing, 
for  instance :  (1)  Cold  stone  and  cold  tar. 
(2)  Cold  stone  and  hot  tar.  (3)  Hot  stone 
and  hot  tar. 

After  the  foundation  of  the  carriage-way 
has  been  thoroughly  rolled  and  consolidated, 
the  tar  macadam  may  be  put  on  in  one  or  two 
layers.  The  usual  depth  is  about  4  in.,  consist- 
ing mostly  of  two  layers.  The  bottom  layer  is 
about  2^  in.  in  depth  and  consists  of  stone 


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MUNICIPAL   AND    SANITAEY  ENGINEERING. 


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2  in.  to  2£  in.  gauge,  well  rolled  ;  the  top  coat 
is  about  1£  in.  in  depth,  and  consists  of  stone 
|  in.  to  1  in.  gauge.  This  is  then  thoroughly 
rolled  and  covered  with  fine  shingle. 

SEALED  ROADS. — These  are  roads  which  are 
surfaced  with  "  binders  "  such  as  "  Tarvia."  In 
such  instances  not  only  has  dust  been  reduced 
to  a  minimum,  but  the  cost  of  cleansing  has 
also  been  reduced.  The  system  of  binding 


covered  with  a  mixture  of  dehydrated  gas  tar 
and  refined  rock  pitch,  in  the  proportion  of 
8  Ibs.  of  pitch  to  a  barrel  of  tar.  This  mixture 
is  poured  over  the  surface  in  a  boiling 
condition  and  sprinkled  with  lias  lime.  This 
is  then  covered  with  a  layer  of  tar  concrete 
about  1J  to  2  in.  in  thickness;  this  also 
being  sprinkled  with  lias  lime,  and  before 
rolling  covered  with  macadam  to  a  depth  of 


FIG.  1. — Single  Sealed  Road. 


with  "  Tarvia,"  as  suggested  by  the  manu- 
facturers, is  as  follows : — The  road  surface 
is  levelled  and  covered  with  a  mixture  of 
Tarvia  and  chippings  about  f  in.  in  thickness, 
1  cu.  yd.  covering  about  36  superficial  yards. 
On  the  top  of  this  layer,  a  coating  of  2  in. 
roadstone  is  laid,  and  in  such  a  manner  that 
1  ton  covers  11  or  12  superficial  yards. 


3  to  4  in.  The  whole  is  then  rapidly  rolled, 
to  adjust  the  layers,  and  afterwards  slowly 
rolled  and  lightly  watered.  The  effect  of  this 
method  is  to  force  the  fine  tar  concrete  into 
the  top  surface  covering,  thereby  filling  the 
interstices  and  binding  the  surfaces  together. 
The  road  surface  has  stood  well  and  reduced 
the  amount  of  dust  considerably.  Another 


Clean  Road  Macadam, 
machine  broken   with 
riddle  2%  holes 


2  Layer  of  Quarry  Si  Ft  ings 
made  into   Tar  Concrete 


Foundation    grouted 
with  Hot  Tar   Compound 


FIG.  2. — Double  Sealed  Eoad. 


The  whole  is  then  lightly  rolled,  the  effect  of 
which  is  to  force  the  binder  up  into  the  top 
surface  thus  filling  in  all  the  interstices  and 
providing  thereby  a  waterproof  surface.  The 
operation  is  completed  by  a  top  sealing  with 
hot  Tarvia.  Dry  chippings  are  then  spread 
on  the  surface  and  the  whole  well  rolled.  A 
system  that  has  been  adopted  in  Penzance  is 
as  follows : — After  the  old  macadam  has  been 
scarified  and  carted  away,  the  surface  is 


method  adopted  at  Penzance  for  coating  the 
surface  of  gradients,  with  due  regard  to  the 
dust  evil,  was  the  use  of  a  preparation  of  dis- 
tilled tar,  rock  pitch,  and  lias  lime,  under  the 
coating  of  macadam.  The  surface  being  thus 
rendered  impervious  to  wet,  and,  while  retain- 
ing its  rigidity,  afforded  a  good  foothold  for 
horses.  Before  calling  attention  to  some 
of  the  dust  palliatives  and  machines  on 
the  market,  there  are  one  or  two  methods 


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of  dressing  the  finished  surface  of  the  road- 
way to  reduce  the  amount  of  dust.  The 
materials  used  form  a  tar  cement  and  in 
some  cases  consist  of  tar,  pitch,  and  lias  lime. 
The  material  should  be  applied  to  the  road  sur- 
face in  a  hot  condition,  and  when  laid  should 
be  sprinkled  with  fine  stone  chippings  about 
^th  of  an  inch,  and  the  whole  well  rolled.  It 
will  be  found  that  this  material  forms  a 
cushion  to  the  road  surface,  and  reduces 
wear  and  tear.  Another  method  which  has 
given  excellent  results  and  is  inexpensive 
is  as  follows : — The  road  surface  should  be 
thoroughly  brushed  and  kept  dry  to  receive 
the  material.  The  mixture  is  made  of  sand, 
chippings  and  shell,  added  to  which  is  a 
quantity  of  tar.  The  whole  is  then  mixed  to 
a  mastic  state,  and  then  sprinkled  over  the 
road  surface  to  a  depth  varying  from  |  in.  to 
f  in.  The  surface  is  then  sprinkled  with 
shell  and  rolled  with  a  hand  roller.  The 
cost  of  this  material  laid  is  about  2Jd.  per 
superficial  yard. 

Dust  palliatives  still  occupy  an  impor- 
tant position  in  connection  with  the  problem 
of  prevention  of  dust,  as  many  of  our 
roads  are  of  macadam,  and  the  expense 
involved  in  removing  the  top  surface  and 
substituting  one  that  will  minimise  the 
amount  of  dust,  such  as  tar  macadam,  as- 
phalte,  &c.,  would  be  prohibitive,  and  the 
attention  of  engineers  has,  therefore,  been 
directed  towards  less  costly  methods. 

DUST  PALLIATIVES. — In  order  that  these 
may  be  successful,  road  surfaces  must  be 
thoroughly  swept  and  freed  from  dust  and 
the  work  of  treating  the  surface  carried  out 
in  fine,  dry  weather  ;  otherwise  the  first 
heavy  vehicle  passing  over  the  treated  area 
will  begin  the  work  of  destruction  and  in  a 
short  time  the  whole  surface  will  be  rendered 
very  unsatisfactory  and  present  large  quan- 
tities of  objectionable,  dangerous  mud. 

CRUDE  TAR  has  been  extensively  used  as  a 
dust  palliative  with  excellent  results.  Care 
must  be  exercised  in  the  boiling  of  the  tar,  as 
more  than  3  %  of  water  in  the  tar  causes 
trouble  during  the  boiling.  The  tar  is  heated 


to  about  200°  F.,  poured  on  the  road,  and 
then  brushed  into  the  surface,  or  spread  by 
the  aid  of  special  machines.  After  the 
surface  has  been  thoroughly  treated,  fine 
chippings  are  sprinkled  over  it — these  being 
more  suitable  than  sand.  The  action  of  the 
traffic  causes  the  tar  and  chippings  to  form 
an  impervious  cushion  on  the  surface  of 
the  road.  The  work  should  be  carried  out 
during  warm  weather.  The  cost  works  out 
at  Id.  to  3d.  per  super  yard.  A  good 
and  effective  method,  and  one  which  adds 
considerably  to  the  life  of  the  road,  is  to 
cover  the  surface  with  tar  at  the  beginning 
of  the  summer  and  another  coat  in  Septem- 
ber, this  method  keeping  the  tarred  cushion 
surface  of  the  road  in  good  condition  during 
the  winter,  thereby  making  it  easier  to 
prepare  the  surface  for  the  next  summer's 
coat  of  tar. 

DISTILLED  TAR,  from  which  the  light  oils 
and  other  compounds  have  not  been  extracted, 
is  an  exceedingly  good  dust  preventer. 

Distilled  tar  thinned  by  the  addition  of 
the  residuurns  of  petroleum  oils  in  the  pro- 
portion of  1  pint  of  petroleum  to  2  gallons 
of  coal  tar  is  a  good  palliative,  when  mixed 
and  applied  cold.  The  treated  surface  should 
be  sprinkled  with  fine  chippings. 

The  same  preparation  with  the  addition  of 
1  pint  of  lias  lime  to  the  above  proportions 
of  petroleum  and  tar  gives  a  thicker  material 
which  is  almost  as  readily  applied. 

CARBURETTED  WATER-GAS  OIL  TAR. — This 
material  is  largely  used  in  many  districts 
where  water-gas  is  manufactured.  It  is  a 
much  thinner  liquid  than  coal  tar,  and  can  be 
sprinkled  over  the  surface  by  means  of  an 
ordinary  water  cart.  Heating  is  not  necessary, 
it  being  applied  cold.  Fine  chippings  should 
be  sprinkled  on  the  surface. 

Before  treating  of  other  palliatives,  a  word 
or  two  may  be  necessary  about  the  boiling  and 
distilling  of  crude  tar.  Care  must  be  exercised 
in  the  process  so  that  the  material  is  not 
burnt  or  overheated.  The  water  will  rise  to 
the  surface  and  can  then  be  removed  by  the 
•use  of  a  flat  tin  shovel.  Overheating  destroys 


144 


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MUNICIPAL   AND   SANITAKY  ENGINEEEING. 


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the  essential  oils  in  the  tar  and  the  work 
invariably  results  in  failure. 

APPARATUS  FOE  SPREADING  TAR. — There  are 
many  machines  for  spreading  tar,  that  have 
from  time  to  time  been  placed  upon  the 
market.  In  smaller  districts,  where  economy 
has  to  be  exercised,  it  will  be  found  that  an 
ordinary  street  watering  cart,  fitted  with  a 
special  tar  spraying  attachment  in  place  of 
the  sprinkler  box,  will  be  found  useful,  where 
the  work  is  finished  by  the  hand  broom. 
Where  only  small  quantities  of  work  have  to  be 
done,  a  small  apparatus  such  as  the  Simeon's 
tar-spraying  and  painting  machine,  or  the 
machine  supplied  by  the  P.  A.  S.  Distributors, 
Ltd.,  will  answer  the  purpose.  The  latter 
machine  is  also  capable  of  doing  large  quan- 
tities of  work,  and  an  experiment  recently 
witnessed  by  the  writer  proved  highly  satis- 
factory. The  cost  of  the  machine  is  about 
£45.  It  is  claimed  by  the  manufacturers 
that  boiling  over  of  the  tar  is  prevented.  The 
Figure  opposite  is  a  rough  line  section 
through  the  boiler.  The  tar  is  placed  in 
the  internal  section  and  percolates  through 
perforations  in  the  sides  into  the  lower 
cavity  of  the  external  drum.  The  tar  in 
this  section  when  brought  up  to  the  required 
heat  is  drawn  up  the  pipe  and  pumped  by 
a  hand  pump  into  the  distributor.  This  dis- 
tributor has  three  or  four  sprays  attached  to 
an  arm.  This  arm  is  attached  to  a  single 
wheel  which  is  worked  by  one  man.  By  this 
arrangement,  the  man  working  the  sprays 
can  walk  forward  and  keep  to  a  line,  no  por- 
tion of  the  work  having  to  be  traversed  by  the 
man.  Each  spray  will  cover  about  15  in. 
at  each  application,  the  combination  of  four 
covering  about  4  ft.  The  cost  of  the  tar 
and  men's  time  spreading,  fuel,  carriage,  &c., 
is  about  3d.  per  super  yard. 

The  machine  which  has  given  the  best 
all  round  satisfaction  was  invented  by  Mr. 
Thomas  Aitken,  a  gentleman  who  has  given 
the  subject  of  road  construction  more  than 
ordinary  attention,  and  whose  tar-spraying 
plant  has  received  the  highest  commendation. 
The  "  Tarspra "  apparatus  can  be  attached 


to  an  ordinary  water  van,  drawn  by  either 
horse  or  tractor.  This  apparatus  is  con- 
structed with  an  air  receiver,  into  which  air 
is  pumped  and  kept  at  a  constant  pressure  of 
100  Ibs.  per  square  inch  on  the  pressure 
gauge.  Tar  is  then  pumped  into  this  receiver, 
increasing  the  pressure  to  about  220  Ibs.  The 
tar  is.  sprayed  on  the  road  through  a  series 
of  nozzles  at  a  constant  pressure  of  about 
200  Ibs.  per  square  inch. 


TO  POMP 


SECTION     OF 

PATENT  "CANTAR','  CONTINUOUS-HEATING. 
SAFETY  TAR  BOILER 

OILS. — Oil  has  been  largely  used  as  a  dust 
preventer,  petroleum  being  used  some  eight 
or  nine  years  ago  in  America.  The  oil 
should  be  highly  heated  and  put  on  the  road 
during  a  very  hot  day,  and  afterwards  covered 
with  sand.  Undoubtedly  the  best  method  is 
to  treat  it  in  the  same  way  as  a  tar  binder, 
a  hard  and  firm  covering  being  thereby 
obtained.  Other  coatings  of  oil  can  then  be 
sprinkled  on  the  surface  to  fill  up  the  inter- 
stices remaining,  and  to  give  a  smooth 
impervious  surface.  All  petroleum  oils  are 
not  satisfactory,  and  only  those  should  be  used 
which  have  an  asphalte  base. 

It  has  been  contended  that  when  the 
wet  season  commences,  the  surface  thus 
treated  becomes  very  greasy,  and  objectionable 
mud  is  formed,  necessitating  thorough  cleans- 
ing of  the  road  surface. 


M.S.E. 


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PROPRIETARY  PREPARATIONS.  -  -  There  are 
many  patent  preparations  for  dust  prevention 
on  the  market,  but  only  a  few  can  be  men- 
tioned. 

"  Akonia "  is  the  patent  process  of  Mr. 
Dan  de  Liebhaber,  and  has  been  used  with 
considerable  success  in  a  large  number  of 
districts.  The  following  advantages  are 
claimed  for  this  material  by  the  patentee:  — 
"  Akonia  "  is  cheaper,  in  most  cases,  than 
ordinary  watering  when  applied  at  the  rate  of 
250  applications  a  year.  It  is  not  only  a  dust 
preventer,  but  also  acts  as  a  road  preserver 
and  improver,  by  rendering  the  surface  hard 
and  smooth,  thereby  diminishing  the  dis- 
integration of  the  macadam,  and  reducing 
the  cost  of  scavenging.  It  is  absolutely 
odourless,  and  free  from  emanations  of  any 
kind,  uninjurious  to  health,  does  not  damage 
tyres,  metal,  clothes,  horses'  hoofs,  &c.,  or 
render  the  road  slippery  and  cloggy. 

It  does  away  with  the  mud  which  invari- 
ably follows  ordinary  watering,  and  renders 
the  road  less  muddy  in  wet  weather.  It 
requires  no  special  appliances  beyond  an 
ordinary  water  cart,  and  can  be  kept  for  any 
length  of  time  without  losing  its  properties. 
"  Hahnite  "  is  an  insoluble  liquid,  which 
oxidizes  when  sprayed  on  to  the  road  and 
forms  an  impervious  and  durable  coating  over 
the  surface.  It  is  claimed  for  "Hahnite" 
that  it  preserves  the  road,  causes  no  injury  to 
tyres,  varnish,  horses,  or  pedestrians,  reduces 
the  sound  of  traffic,  acts  as  a  disinfectant,  pre- 
vents dust  from  rising,  and  minimises  the 
formation  of  mud. 

The  use  of  this  material  compares  favour- 
ably with  ordinary  street  watering,  and  is 
applied  to  the  road  by  a  street  watering  cart. 

Calcium  chloride,  which  is  manufactured 
at  Northwick,  Cheshire,  is  an  excellent  dust 
preventer.  A  small  quantity  of  these 
crystals  are  placed  in  an  ordinary  watering 
cart,  and  allowed  to  dissolve  in  the  water, 
thus  forming  a  cheap  dust  palliative  capable 
of  producing  good  results,  and  of  considerably 
reducing  the  cost  of  watering.  (See  "  EOAD 
WATERING.")  B.  H.  B.  &  F.  L. 


Earth  Closets. — Useful  apparatus  in  the 
country,  but  unsuitable  for  use  on  a  large 
scale  or  in  populous  districts,  owing  to  the 
quantity  of  suitable  earth  required.  Where 
water-closets  are  not  practicable  and  the  con- 
ditions are  favourable,  earth  closets  form  the 
best  substitutes,  as  the  earth  made  use  of  not 
only  keeps  the  excreta  dry,  but  also  deodorises 
it  and  disintegrates  the  organic  matter  and 
converts  it  into  the  condition  in  which  it 
naturally  exists  in  fertile  soil.  It  is  essential 
that  the  earth  used  should  be  suitable.  It 
must  be  dry,  finely  sifted,  and  of  a  loamy 
nature,  and  from  1  to  2  pints  must  be 
spread  over  the  excreta  whenever  the  closet  is 
made  use  of.  An  earth  closet  may  simply 
consist  of  a  seat  fixed  over  a  suitable  recep- 
tacle, which  is  easily  removed  for  emptying  ; 
the  earth  being  in  this  case  stored  in  a  box 
and  applied  by  hand  with  a  trowel.  A  better 
apparatus  is  that  in  which  the  earth  is 
applied  automatically,  as  in  the  case  of  Moule's 
earth  closet.  In  this  a  hopper  is  provided 
.  behind  and  above  the  seat  capable  of  storing 
a  sufficient  amount  of  earth  to  last  for  some 
little  time.  Connected  with  this  is  a  valve 
into  which  a  measured  quantity  of  earth  falls, 
and  which,  being  worked  by  a  handle  or  by  a 
lever  connected  with  the  seat,  distributes  the 
earth  over  the  excreta  when  the  handle  is 
pulled  or  a  person  rises  from  the  seat.  When 
the  handle  is  released  or  a  person  again  sits 
upon  the  seat,  the  valve  is  recharged  with  the 
requisite  amount  of  earth.  No  moisture 
other  than  that  of  the  excreta  and  urine  should 
be  admitted  to  the  closet.  The  apartment  in 
which  an  earth  closet  is  fixed  should  not  have 
any  direct  communication  with  a  dwelling. 
It  should  be  well  lighted  and  ventilated,  and 
should  be  provided  with  an  impervious  floor 
raised  some  few  inches  above  the  ground  level. 

Economisers  or  Feed- Water  Heaters. 

— Accessory  appliances  used  in  connection  with 
steam  boiler  plants  for  the  purpose  of  effecting 
a  saving  in  fuel  by  utilising  the  waste  heat  in 
the  flues  for  the  purpose  of  heating  the  feed- 
water  to  the  boiler.  This  object  is  achieved 


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in  different  ways — (a)  by  intercepting  and 
utilising  part  of  the  heat  of  the  gases  from 
the  boiler  furnaces  as  soon  as  they  leave  the 
boiler ;  (li)  by  passing  the  feed  through  a 
vessel  jacketed  with  exhaust  steam,  or  using 
live  steam  in  a  similar  manner.  In  principle, 
the  "  economiser  "  is  really  a  supplementary 
boiler  working  within  a  low  range  of 
temperature  and  whereby  a  saving  of  fuel 
can  be  secured,  say,  from  10  to  15  %.  For 
example,  a  boiler  working  at  a  steam  gauge  pres- 
sure of  150  Ibs.  per  square  inch  with  boiler- 
feed  at  32°  F.,  will  consume  1,193  thermal 
units  per  1  Ib.  of  water  evaporated,  as  com- 
pared with  1,013  units  when  using  feed-water 
at  212°  F.,  thus  showing  a  saving  of  15  %  of 
the  heat  required.  To  secure  the  greatest 
real  economy  the  temperature  of  the  feed- 
water  should  be  at  a  maximum  with  a 
minimum  of  fuel-cost.  One  of  the  best- 
known  appliances  for  realising  the  advantages 
to  be  gained  by  the  first  method  (a)  is  "  Green's 
fuel  economiser,"  which  is  a  flue-heated  feed- 
water  heater.  It  consists  of  sections  or  rows 
of  cast-iron  tubes  (4|  in.  diameter  by  9  ft. 
long)  fixed  in  an  enlargement  of  the  main 
flue.  The  accumulation  of  soot  which  takes 
place  on  the  pipes  is  removed  by  slow-moving 
scrapers  (the  invention  of  Mr.  Green)  upon 
their  external  surfaces.  The  size  of  economiser 
required  for  any  given  plant  is  calculated 
on  the  evaporative  capacity  of  the  boilers, 
but  approximate  rules  such  as  the  pro- 
vision of  one  pipe  for  every  three,  I. H. P., 
or  4  pipes  per  ton  of  coal  per  week  of 
56  hours,  are  useful  guides.  The  hot 
flue  gases  may  be  reduced  in  temperature 
from  650°  F.  to  350°  F.,  and  the  feed-water 
heated  some  150°  F .  to  250°  F.  Each  pipe  has 
10  sq.  ft.  of  heat  absorbing  surface  and  a 
water  capacity  of  6J  gallons.  Another  useful 
apparatus  is  the  "  Hudson  economiser  "  which 
is  also  a  steam  condenser,  is  of  simple  con- 
struction, and  has  no  tubes,  so  that  renewal 
of  parts  is  reduced  to  a  minimum.  This 
apparatus  extracts  the  grease  from  the  exhaust 
steam  before  coming  in  contact  with  the  cold 
feed.  The  purified  steam  thus  obtained  comes 


in  direct  contact  with  the  cold  feed  entering 
the  top  chamber  of  the  apparatus  through  a 
spray,  the  water  being  nearly  boiled.  Softened 
water  is  thus  obtained,  free  from  oil,  at  from 
200°  F.  to  210°  F.,  for  purposes  of  boiler  feed. 
The  apparatus  thus  possesses  the  further 
advantage  of  preventing  incrustation  on  the 
interior  of  boiler  shell  or  tubes. 

Exhaust- steam  feed-heaters  are  also  largely 
used,  and  an  average  economy  of  about  15  % 
is  obtainable  between  a  cold  boiler  feed  at 
55°  F.  and  water  at  212°  F.  In  the  "  Row 
feed- water  "  heater  a  patent  indented  tube  is 
used  which  is  claimed  as  being  twice  as 
efficient  as  an  equal  amount  of  plain  tube 
surface.  For  good  water,  not  liable  to  scale, 
the  t  steam  circulates  around  the  outsides  of 
the  tubes  through  which  the  water  passes. 
For  bad  water  this  order  is  reversed. 

Efflorescence. — This  is  a  term  applied  to 
a  peculiar  powdery  substance  which  occa- 
sionally appears  on  the  faco  of  new  brick  or 
stone  work.  As  a  rule  it  arises  from  an 
excess  of  salts  in  the  bricks  or  stone,  which 
become  dissolved  in  water  from  heavy  rain. 
Usually  the  efflorescence  consists  largely  of 
sulphate  of  magnesia.  The  cure  is  difficult, 
but  a  periodical  washing  down  with  diluted 
hydrochloric  acid,  applied  by  means  of  a 
sponge,  is  to  be  recommended. 

Ejectors.  —  Hydro-pneumatic  " ejectors," 
for  lifting  sewage  by  the  employment  of 
compressed  air,  now  often  replace  centri- 
fugal and  lift  pumps,  and,  in  suitable 
circumstances,  have  many  advantages  for 
such  work.  The  principle  upon  which  the 
apparatus  works  will  be  understood  from  an 
inspection  of  Fig.  1,  which  is  a  sectional 
diagram  of  "Coombs"  pneumatic  ejector  as 
installed  for  raising  crude  sewage,  and  other 
liquids,  by  compressed  air.  The  apparatus 
consists  of  a  wrought-steel  or  cast-iron  body  or 
container  C.,  provided  with  inlet  and  outlet 
sewage  flap  valves  /.  V.  and  O.  V.,  sluice  valves 
S.  F.I  and  S.  F.2,  for  disconnecting  the  ejector, 
and  two  floats  T.  F.,  and  B.  F.,  which  operate 
the  automatic  valve  A.  V.  which  controls  the 


147 


EJE 


ENCYCLOPEDIA   OF 


EJE 


supply  of  compressed  air  and  the  exhaustion 
of  same  after  ejection  of  the  sewage.  In 
actual  work  the  sewage  flows  from  the  gravita- 
tion sewers  into  the  container  C.,  through  the 
inlet  flap  valve  /.  V.  until  it  is  full,  when  the 
top  float  T.  F.  rises  and  opens  the  automatic 
valve  A.  V.  to  the  compressed  air  supply, 
closing  it  to  exhaust  at  the  same  time.  The 
sewage  is  then  discharged 
through  the  outlet  flap  valve 
O.  r.,  by  the  pressure  of  the 
compressed  air,  and  the  body 
of  the  ejector  is  quickly 
emptied.  When  the  container 
C.  is  nearly  empty,  the  bottom 
float  B.  F.  falls  and  closes  the 
automatic  valve  A.  V.  to  com- 
pressed air  supply,  and  at  the 
same  time  opens  the  valve  to 
exhaust,  so  allowing  the  com- 
pressed air  to  escape,  after 
which  a  fresh  charge  of 
sewage  flows  into  the  con- 
tainer, thus  beginning  another 
cycle  of  operations  as  above 
described.  The  working  of  the 
apparatus  is  automatically  re- 
peated so  long  as  there  is  a 
flow  of  sewage  and  a  supply  of 
compressed  air.  Attendance 
is  only  required  at  the  ejector 
chamber  for  periodical  inspec- 
tion. The  rate  of  discharge 
depends  upon  the  time  of 
filling,  and  the  ejector  will 
automatically  adapt  itself  to 
the  variations  of  sewage  flow.  Ejectors  are 
sometimes  placed  in  pairs, and  maybe  arranged 
to  work  either  independently  or  alternately  so 
as  to  give  a  continuous  delivery  of  sewage. 

The  compressed  air  for  actuating  the  ejector 
is  commonly  produced  at  some  central  station 
and  transmitted  to  the  ejectors  in  different 
parts  of  the  district  as  may  be  required.  The 
air  mains  consist  of  cast-iron  pipes,  as  used 
for  water  supply  purposes,  with  spigot  and 
socket  joints,  caulked  with  lead  and  yarn. 
Generally  speaking,  the  use  of  compressed 


air  as  a  motive  power  is  not  found  economical 
in  fuel  costs,  but  this  does  not  apply  to  the 
same  extent  in  the  case  of  ejectors  lifting 
sewage  as  ordinarily  applied.  The  total  cost 
under  all  heads  of  expenditure  must  be  con- 
sidered in  estimating  the  value  of  the  system 
in  any  given  case.  For  ejector  work,  low 
pressures  such  as  from  15  Ibs.  to  25  Ibs. 
are  the  normal  conditions  met  with,  and 
the  percentage  of  loss  is  much  less  than 
in  the  case  of  higher  pressures.  For 
greater  pressures  two-stage  compression 
is  necessary,  but  ejector  work  is  generally 
below  the  limit  for  the  advantageous 
employment  of  stage  compression.  Con- 
siderable improvements  have  been  made 
of  recent  years  in  the  compressors 


FIG.  1. — "Coombs 


Pneumatic  Ejector.     (Daniel  Adamson  &  Co.) 

employed,  and  the  modern  high-speed  com- 
pressor, with  mechanically-operated  valves, 
gives  a  much  greater  efficiency  than  the 
earlier  type  of  low-speed  compressor  fitted 
with  lift-valves.  In  the  drainage  of  many 
towns  it  is  an  advantage  to  be  able  to  divide 
the  area  into  a  number  of  independent  drain- 
age areas,  and  to  such  a  condition  the  ejector 
system  favourably  lends  itself,  as  the  ejectors 
can  be  conveniently  worked  from  one  central 
compressor  station.  The  system  is  applicable, 
in  general,  where  low-level  sewage  has  to  be 


148 


EJE 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


ELE 


lifted  to  higher  parts  of  the  district,  into 
intercepting  or  outfall  sewers,  for  delivering 
sewage  in  low-lying  areas  out  to  sea  during  any 
state  of  the  tide,  and  also  in  level  country  where 
to  secure  self-cleansing  gradients  deep  and  ex- 
pensive cuttings  would  be  involved  in  a  purely 
gravitation  scheme  of  drainage.  The  mode 
of  fixing  an  injector  in  a  brick  underground 
chamber  and  connecting  it  with  the  gravitation 
sewer  on  the  one  side,  and  with  a  rising  or 
delivery  main  on  the  other,  is  shown  in  Fig.  2. 


FIG.  2. 
"  Coombs'1  Ejector  in  Chamber. 


(Daniel  Adamson  &  Co.) 


Electricity.  —  Introduction  and  Defini- 
tion —  Components  of  Electricity  —  Electric 
Lighting  —  Flame  Arc  Lamps  —  Incandescent 
Lamps  —  The  Electricity  Works  —  Systems  of 
Charging  for  Electricity — Electricity  Meters — 
Transforming  Stations  and  Apparatus — Electric 
Motors. — No  useful  purpose  would  be  served 
by  endeavouring  in  this  article  to  define  and 
explain  the  term  electricity  in  the  sense  in 
which  it  is  used  by  the  physicist.  As  used  by 
the  engineer,  electricity  has  come  to  -denote 
a  form  of  energy.  The  independent 
use  of  the  word  in  these  two  senses 
rarely  leads  to  misunderstanding.  The 
physicist  in  his  "  electronic  theory  of 
matter "  states  that  the  atoms  of 
matter  themselves  are  made  up  of 
"  electrons  "  (hypothetical  concentrated 
units  of  negative  electricity) ;  each 
aggregation  of  electrons  being  sur- 
rounded by  a  sphere  of  positive  elec- 
tricity, and  that,  consequently,  matter, 
in  its  last  analysis,  is  identical  with 
electricity,  and  consists  of  nothing  else. 
While  the  physicist  appears  to  regard 
this  profound  alleged  knowledge  with 
considerable  satisfaction,  it  is  evidently 
of  very  little  practical  use  to  the 
engineer  or  to  the  layman,  who  have 
for  many  years  considered  electricity 
to  be  something  which,  consumed  in 


In  the  actual  working  of  the  ejector,  there 
are  certain  advantages  which  tend  to  facilitate 
the  raising  of  sewage  by  this  method.  For 
example,  there  are  no  parts  liable  to  be  injured 
by  the  action  of  the  sewage  or  of  grit  upon 
them,  and  the  working  parts  are  few  and  not 
likely  to  get  out  of  order.  The  sewage  inlet 
and  outlet  valves  are  in  excess  of  the  full 
area  of  the  delivery  pipe,  and  a  free  passage 
is  given  for  the  carrying  away  of  all  solids 
which  drop  direct  into  the  delivery  passage 
sloping  towards  the  outlet,  and  are  thus 
removed  by  the  first  flush  of  liquid  from  the 
container.  Previous  screening  of  the  sewage 
is  thus  unnecessary,  an  advantage  over 
pumping  plants  where  periodical  cleansing 
of  screens  and  sump  wells  is  essential. 


sufficient  quantities,  serves  to  provide  light 
and  heat,  and  to  propel  tramcars  and  railway 
trains,  and  to  drive  machinery  in  workshops 
and  factories.  Light,  heat,  and  work  are 
well  known  to  be  forms  of  energy.  It  is 
furthermore  well  known  that  energy  may  be 
converted  from  one  form  into  another.  To 
the  engineer  and  layman,  electricity  is  also  a 
form  of  energy.  At  present,  the  engineer 
deals  with  electricity  as  something  which  can 
be  bought  and  sold  in  definite  quantities,  and 
his  purposes  are  sufficiently  served,  therefore, 
by  simply  regarding  electricity  as  a  form  of 
energy. 

COMPONENTS  OF  ELECTRICITY. — Electricity 
may  be  sub-divided  into  three  components : 
(1)  Pressure,  (2)  Current,  (3)  Time. 


149 


ELE 


ENCYCLOPEDIA   OF 


ELE 


In  engineering  calculations  the  units  in 
which  these  components  are  expressed  are — 

The  unit  of  pressure  =  the  volt. 

The  unit  of  current  =  the  ampere. 

The  unit  of  time  =  (usually)  the  hour. 
Electricity  is  used   commercially   in   one   or 
other  of  two  forms  : 

I.  Continuous  electricity. 

II.  Alternating  electricity. 

In  the  first  of  these,  the  direction  of  the 
current  is  constant,  whereas  in  the  second 
the  current  alternates  in  direction  many  times 
per  second.  A  detailed  consideration  of  the 
theory  of  these  two  forms  of  electricity  cannot 
be  undertaken  in  this  article,  but  the  appro- 
priate use  for  each  form  will  be  set  forth  in  a 
later  section  of  it. 

The  following  explanations  of  terms,  although 
they  should  be  taken  as  applying  strictly  only 
to  continuous  electricity,  are  in  most  instances 
substantially  true  of  alternating  electricity. 
Any  quantity  of  electricity  is  made  up  of  the 
product  of  the  three  components,  pressure, 
current,  and  time.  The  unit  of  electricity  is 
the  kilowatt  hour,  sometimes  called  the  Board 
of  Trade  unit,  or  merely  the  unit.  It  is  pre- 
ferable to  employ  the  .  term  kilowatt  hour 
(kw.  hr.).1  A  quantity  of  electricity  in  kilo- 
watt hours  is  equal  to  1,000  times  the  product 
of  the  pressure  in  volts,  the  current  in  amperes 
and  the  time  in  hours.  In  other  words : 
Kilowatt  hours  =  1,000  X  volts  X  amperes 
x  hours.  The  above  is  the  equation  for  the 
quantity  of  energy. 

Power  is  the  rate  of  expenditure  or  trans- 
formation of  energy.  Consequently  power 
is  expressed  in  kilowatt  hours  per  hour,  i.e., 
in  kilowatts.  The  power  equation  is  thus 
obtained  by  dividing  both  sides  by  the  time 
in  hours.  We  thus  have  for  the  power 
equation  : 

TZM  1,000  X  volts  X  amperes  X  hours 

Kilowatts  =  - 

Hours 

i.e.,  kilowatts  =  1,000  X  volts  X  amperes. 

Thus  when  energy  is  being  delivered  over 
a  circuit  at  the  rate  of  one  kilowatt-hour  per 

1  It  has  been  suggested  that  the  term  "  kelvin  "  be 
employed  in  place  of  the  term  "  kilowatt  hour." 


hour  (or  of  one  "  unit  "  per  hour)  the  power 
being  transmitted  is  one  kilowatt. 
One  kilowatt  =  1*34  horse  power. 
One  kilowatt- hour  =  1'34  horse  power  hour. 
One  kilowatt  =  1,000  watts. 
Since  kilowatts  =  1,000  x  volts  x  amperes 
watts  =  volts  x  amperes. 
In  the  case  of  a  conductor  of  given  dimen- 
sions and  material,  a  certain  pressure  in  volts 
is  required  to  send  through  the  conductor  a 
current  of  one  ampere.     The  conductor  is  said 
to  have  a  certain  resistance.     This  resistance 
is  expressed  in  ohms,  and  is  equal  to  the  volts 
divided  by  the  amperes.     Thus : 

•D     •  ,          /•      ,       N         Pressure  (in  volts) 
liesistance  (in  ohms)  =  7^- 

Current  (in  amperes) 

or 

Volts 
Ohms  =  -T 

Amperes. 

This  is  known  as  Ohm's  law,  in  honour  of 
Dr.  Ohm,  its  discoverer. 

Electricity  is  employed  for  obtaining  work, 
light,  and  heat ;  i.e.,  energy  in  the  form  of 
electricity  is  converted  into  energy  in  these 
other  forms.  The  most  extensive  of  these 
commercial  applications  of  electricity  is  to 
lighting,  but  during  recent  years  the  electrical 
operation  of  tramcars  has  also  assumed  great 
importance.  Electricity,  as  a  source  of  me- 
chanical energy,  is  appropriate  not  only  for 
propelling  tramcars,  but  for  many  other 
industrial  processes,  as  for  driving  mills  and 
workshops,  and  for  dockyards  and  harbours. 
The  application  of  electricity  to  heating  and 
cooking  is  now  reduced  to  a  commercial  basis 
and  bids  fair  to  soon  assume  an  importance 
commensurate  with  the  use  of  electricity  for 
lighting. 

ELECTRIC  LIGHTING. — Electric  lamps  may  be 
divided  into  two  great  classes  : 

I.  Arc  Lamps. 
II.  Incandescent  Lamps. 

Each  of  these  classes  comprises  a  large 
number  of  types,  and  it  will  be  necessary  to 
restrict  the  scope  of  our  inquiry  to  the  most 
modern  representative  of  each  class.  I.  The 
so-called  "flame"  arc  lamp  has  only  come 
into  extensive  use  during  the  last  three  years. 


150 


ELE 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


ELE 


It  is  far  more  economical  than  any  other  type 
of  arc  lamp  and  has  largely  supplanted  other 
types.  II.  During  the  same  period,  i.e.,  during 
the  last  four  years,  a  great  advance  has  also 
been  made  in  incandescent  lamps.  This  has 
related  to  the  extensive  commercial  intro- 
duction of  the  metal  lamp.  This  is  a  lamp 
with  a  metallic  filament  and  it  is  rapidly 
supplanting  all  forms  of  incandescent  lamps 
with  carbon  filaments.  The  metal  lamp  con- 
sumes, for  a  given  candle-power,  less  than 
one-third  as  much  energy  as  is  consumed  by 
the  carbon  lamp ;  consequently,  in  spite  of 
its  somewhat  greater  first  cost,  its  use  is 
attended  by  large  ultimate  economy. 

FLAME  ARC  LAMPS. — One  of  the  several  excel- 
lent types  of  flame  arc  lamp  now  on  the  market 
is  illustrated  in  Fig.  1.  The  widest  and  most 
appropriate  field  for  the  use  of  flame  arc 
lamps  is  in  the  lighting  of  streets,  parks, 
docks,  railway  yards  and  other  open  spaces, 
and  also  for  the  interior  illumination  of  large 
halls,  warehouses,  theatres,  factories,  work- 
shops and  railway  stations.  In  Fig.  I  A.  A.  are 
two  carbon  rods  between  the  lower  extremities 
of  which,  the  flaming  arc  is  formed.  The 
carbons  are  slowly  consumed  and  in  order 
that  the  arc  may  remain  at  the  same  point, 
the  carbons  as  they  burn  away  are  slowly  fed 
downward  by  means  of  the  electromagnetic 
mechanisms  seen  in  the  upper  part  of  the 
case  of  the  lamp.  When  operated  on  circuits 
supplying  continuous  electricity,  it  is  custom- 
ary to  run  two  such  lamps  in  series  from  a 
110  volt  circuit,  and  four  lamps  in  series  from 
a  220  volt  circuit.  The  lamps  are  built  for 
various  currents  ;  10  amperes  is,  however,  the 
current  usually  employed.  Thus  two  such 
lamps  consume 

110  X  10  -~  1,100  watts 
or  550  watts  per  lamp. 

A 10  ampere  flame  arc  lamp,  operated  from  a 
circuit  of  continuous  electricity,  gives  out  about 
2,100  candle-power.  Thus  the  consumption  is 

550 
a -mo  —  0'26  watts  per  candle-power. 

A  customary  size  for  the  carbons  of  such  a 
10  ampere  flame  arc  lamp  is  500  mm.  long,  and 


9  mm.  and  8  mm.  diameter  respectively  for  the 
positive  and  negative  carbons.  These  carbons 
must  be  renewed  about  every  11  hours  at 
an  average  cost  of  some  6d.  per  pair  of  carbons. 
This  cost  is  made  up  of,  say,  4d.  for  the  price 
of  the  carbons  and  Zd.  for  the  labour  of 
"trimming"  the  lamp,  i.e.,  replacing  and 
adjusting  the  carbons,  cleaning  the  globe,  and 
maintaining  the  lamp  in  good  condition. 
Thus  the  cost  per  lamp  per  1,000  hours  for 
carbons  and  trimming,  is  some  45s.  The 
price  of  the  electricity  may  be  anywhere 
from  Id.  to  3d.  per  kw.  hr.  In  1,000  hours  the 
lamp  consumes 

1,000  X  0-550  =  550  kw.  hr. 


FIG.  1. — Section  of  Flame  Arc  Lamp. 

Thus  for  total  cost  per  lamp  per  1,000  hours 
we  obtain  the  values  set  forth  in  the  next 
to  the  last  column  of  the  following  table, 
and  the  total  cost  per  candle-power  (c.p.)  per 
1,000  hours  is  given  in  the  last  column  : — 


£8 

i-e-as 

a-o  a 

S£p"»- 

grt 

•2  g  fj 

uS  ~  J« 

§§'"«,/; 

vi  5,9  *  ^ 

& 

^*J8 

5-S-| 

SeSBJ 

||oj|     . 

5-ii 

"11 

0'>j* 

*te*§ 

&"£  *=  2  § 

5  o  <  §3 

C^3  g 

»-«  t, 

uS   OJ1"1 

.??  ^  r^  o 

?-w  S^  c 

-*J  ^ 

•2;s  ^ 

M    S   bOg 

§  w  -S  «  rt~ 

o    - 

£5 

5^3  ft 

O  cH 

H>fe  ft 

O^ 

! 

46 

45 

91 

0-52 

2 

92 

45 

137 

0-78 

3 

138 

45 

183 

1-05 

The  above  costs  are  for  the  naked  arc.     If 
the    arc    is    contained    within     globes,    the 


151 


ELE 


ENCYCLOPAEDIA   OF 


ELE 


candle-power  is  decreased  by  some  15  %  for 
clear  glass,  and  by  some  30  %  for  opal  globes 
and  the  cost  per  candle-power  is  correspond- 
ingly higher.  The  illumination  is  given  in 
terms  of  the  mean  hemispherical  candle- 
power.  If  operated  from  circuits  of  alter- 
nating electricity,  flame  arc  lamps  are 
considerably  less  economical.  With  the  older 
forms  of  arc  lamps  the  inferiority  on  alter- 
nating circuits  is  still  more  marked. 

The  first  cost  of  a  flame  arc  lamp  is 
usually  about  £8  to  £10,  and  since  there  is 
nothing  in  their  construction  to  preclude  a  life 
of  some  10  years,  the  charge  for  interest  and 
depreciation  but  slightly  affects  the  result. 
Taking  interest  and  depreciation  as  amounting 
to  80s.  per  lamp  per  year,  and  assuming 
that  the  lamp  burns  3,500  hours  per  year, 
we  arrive  at  the  annual  cost  per  year  set  forth 
in  the  following  table : — 


:  t  •- 

sll 

If  I*!  if 

o  oT  *"  C 

^s||| 

o  c3  ^  bb 
§  >>o-5 
CM  ^*  £ 

"S.S  'i 

o  »£  ^  r^3     urs  —  • 

|5P 

'SaS.g^ 

•Sdl- 

Ip 

iliSKi 

O  B.S  J 

oic  S^.,  o 

fcHSQM   O   * 

jj    OCO   3 

Sg^o 

O  Pi  o 

1 

318 

30 

348 

2-00 

2 

480 

30 

510 

2-90 

3 

640 

30 

670 

3-83 

It  is  very  difficult  to  generalise  as  to  the 
number  of  lamps  required  to  afford  satis- 
factory outdoor  illumination.  A  correct  idea 
is  best  obtained  by  examples,  a  couple  of 
which  relating  to  London  streets  are  given  in 
the  following  table  : — 


Name 
of 

Street. 

Distance 
between 
Lamps. 

Height 
above 
Ground. 

Width 
of 
Street. 

Type  and  Capacity 
of  Lamp. 

Holborn 

230'  on 

20£' 

82J' 

10  amp.  white  maga- 

either 

zine     flame      arc 

side  of 

mounted  on  post. 

street 

Cannon 

165'  in 

28' 

64' 

11  amp.  yellow  flame 

Street 

middle 

arc    with    central 

of  street 

suspension. 

A  suitable  illumination  may  be  obtained  by 
11  ampere  flame  arc  lamps  with  yellow  flame 
carbons,  spaced  some  250  ft.  apart  on  either  side 
of  the  road  and  20  ft.  from  the  ground,  or 
some  150  ft.  apart  in  the  centre  of  the  road 
and  about  28  ft.  from  the  ground. 

It  has  been  stated  that  the  carbons  must  be 
renewed  by  hand  about  every  11  hours,  but 
recent  developments  in  "  magazine  "  lamps 
have  extended  this  period  to  about  40  hours. 
A  magazine  lamp  employs  6  to  9  pairs  of 
carbons,  which  automatically,  pair  by  pair,  take 
the  place  of  the  burnt  pair.  This  saves  the 
necessity  of  trimming  when  each  pair  has 
burnt  away.  It  has  the  further  advantage 
that  the  carbons  may  be  burnt  to  a  stump. 
By  the  use  of  magazine  lamps  the  cost  of 
trimming  per  1,000  hours  given  in  the  table 
on  p.  151,  may  be  reduced  some  15  % 
whilst  the  total  cost  per  1,000  hours  may  be 
reduced  some  3  to  8%  depending  upon 
the  price  of  electricity  per  unit.  The  longer 
hours  of  burning  of  the  magazine  lamp  is, 
however,  of  doubtful  advantage  for  the  reason 
that  the  light  is  better  and  the  mechanism  is 
kept  in  better  condition  when  the  attendant 
visits  it  frequently,  cleaning  the  mechanism 
and  the  globes  at  each  visit.  The  less  frequent 
attention  given  to  the  magazine  lamp  is  con- 
ducive to  more  rapid  deterioration  of  the 
working  parts. 

INCANDESCENT  LAMPS. — As  already  stated, 
the  metal  lamp  is  by  far  the  most  economical 
and  satisfactory  form  of  incandescent  lamp. 
Formerly  incandescent  lamps  were  used 
almost  exclusively  for  interior  illumination, 
but  since  the  advent  of  the  metal  lamp,  it  has 
also  come  into  fairly  extensive  use  for  out- 
door illumination,  thus  becoming  a  rival  of 
the  flame  arc  lamp,  especially  where  it  is  of 
advantage  to  sub-divide  an  aggregate  candle- 
power  amongst  many  lamps.  Taking  into 
account  the  cost  of  renewing  carbons  it  may 
be  said  that  flame  arc  lamps  are  only  econom- 
ical in  sizes  of  at  least  1,000  c.p.  per  lamp, 
whereas  economical  metal  lamps  may  be 
obtained  in  practically  all  sizes  from  10  c.p.  up 
to  400  c.p. 


152 


ELE 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


ELE 


Let  us  first  fix  our  attention  on  a  50  c.p. 
220  volt  metal  lamp  of  any  one  of  the  excellent 
types  now  on  the  market.  Such  a  lamp  con- 
sumes about  1'3  watt  per  c.p.  Consequently 
the  total  consumption  per  lamp  is 
50  X  1-3  =  65  watts. 

Owing  to  the  greater  effectiveness  obtained  by 
sub-division,  20  such  lamps  with  an  aggregate 
illumination  of 

20  X  50  =  1,000  c.p. 

are  fully  equivalent  to  one  2,000  c.p.  flame  arc 
lamp,  i.e.,  to  a  flame  arc  lamp  of  the  size 
which  has  been  taken  in  the  preceding 
estimate.  The  consumption  of  20  lamps  is 
1,000  X  1'8  =  1,300  watts  as  against  only 
550  watts  for  the  2,000  c.p.  flame  arc  lamp. 
It  will  be  conservative  to  estimate  on  replac- 
ing the  metal  lamps  after  an  average  of  1,200 
hours  in  circuit.  The  price  per  lamp  is  3'75s. 
This  gives  for  the  20  lamps  a  renewal  cost  of 


20  X 


1,000 


X  3'75  =  63s.  per  1,000  hours, 


1,200 

assuming  the  average  life  of  each  lamp  to 
be  1,200  hours.  The  consumption  per  1,000 
hours  for  the  20  lamps  will  be  1,300  kw.  hour. 
Thus  for  the  total  cost  per  1,000  hours  of 
burning,  including  renewals,  we  obtain  the 
values  given  as  follows  for  various  prices  per 
unit  of  electricity. 


|J 

£S  . 

c.i  £2    O 

P£ 

g-y  M  fe 
^  ™  o   . 

<"  T3  •>         £ 

OJ  O 

o  o 

V    L*    VI    .' 
0    CS    fc<    t>0 

g  ®  g.S 

*M     ^*» 

r~i  '"  K 

c  fcc  o 

rt  be    .  Q 

*-*    X 

fe     S 

C^j'S 

O30 

K=W 

d£       o  '~l 

c  ft^ 

„  ^oM 

S  sd  S 

O      w      o 

•-  ^   ^  t® 

'"  ft     —  ^ 

go"" 

43'^-  r 

o  15  8 
-$x   - 

•g  3  &o  8_ 

45  a 

45    ^C0"3 

si 

64J  S 
'5  ft 

6.s" 

0,2  «  c"-1 

HS  J  rH~ 

0   g 

O  ft 

o  g^  o 

O  ftO^ 

1 

108 

63 

171 

2-04 

7-15 

2             216 

63 

279 

3-35 

11-70 

o 

324 

63 

387 

4-65 

16-30 

The  above  table  is  based  on  the  use  of 
lamps  of  50  c.p.  each,  but  there  is  the  alterna- 
tive of  employing  metal  lamps  having  400  c.p. 
per  lamp,  and  consuming  some  440  watts  per 
lamp.  We  may  take  it  that  four  such  lamps, 
giving  an  aggregate  c.p.  of 

4  X  400  =  1,600 c.p., 
will  afford  an  illumination  equivalent  to  the 


2,000  c.p.  flame  arc  lamp  on  the  one  hand,  and 
to  the  twenty  50  c.p.  metal  lamps  on  the  other 
hand.  The  cost  of  these  lamps  is  some  19s. 
each,  and  their  average  life  some  1,000  hours. 
We  thus  obtain  the  cost  per  year  for  running 
four  lamps,  as  set  forth  in  the  following 
table : — 


8g 

SSB 

p. 

"^•P. 

o  o 

fi  0, 

list? 

<£  s 

sgs 

ID    K    — 

-"    °    S            A  ~ 

£'"'  • 

(^  ti'w'S 

V-     r>> 

w  '—  ^ 

C   fcC  o 

o       ^  J^1  —  ~ 

fe    tn 

02           £j 

S-S'S 

CM*S 

(§-SS 

§"    "  ~  '"      — 

Cj   ft  3 

c  ^o  W 

""'3  g 

0  cS 

-^  -8 

""  ^a 

•"  ft§-^ 

gP 

In  ^i""1 

to—    - 

"3  —  ^  -p  ^^i 

4^   0 

•g  °  of^g 

-e  g 

P-l  ft 

oil 

o  _,  r"1 
o.S 

EH  S  S  o  .5 

II 

o  <3i^  u 
O  fto-fl 

1 

147 

76 

223 

1-68 

5-87 

2 

294 

76 

370 

2-78 

9-73 

3 

440 

76 

516 

3-87 

13-50 

These  400  c.p.  lamps  differ  slightly  in 
form  from  the  50  c.p.  lamps,  in  that  they  are 
fitted  with  Edison  screw  caps  instead  of 
bayonet  fittings.  The  reason  for  this  modi- 
fication is  that  the  manufacturers  find  the 
"Edison  screw  cap"  more  suitable  for  running 
on  heavy  currents  than  the  ordinary  bayonet 
holder.  When  comparing  the  running  costs 
of  these  lamps  with  the  equivalent  running 
cost  of  the  flame  arc  lamps,  one  must  keep  in 
mind  that  the  candle-power  of  the  arc  lamp  is 
considerably  reduced  by  deposits  on  the  inner 
globe,  and  this  loss  amounts,  as  stated  before, 
to  some  20  to  30%.  In  order,  therefore, 
to  maintain  the  apparent  advantage  in  effici- 
ency of  the  flame  arc  over  the  metal  lamps, 
the  globes  of  the  arc  lamp  must  be  constantly 
cleaned — an  item  which  will  increase  the  cost 
of  maintenance.  On  the  other  hand  there  is 
no  diminution  of  light  in  the  metal  lamps,  as 
the  globes  remain  clear  and  the  candle-power 
is  maintained  practically  constant  through- 
out their  life.  Moreover  the  life  of  the  metal 
lamps  taken  above  are  conservative  values, 
and  it  is  very  probable  that  1,500  hours 
would  be  more  in  accordance  with  the  facts. 
The  field  of  interior  illumination  by  elec- 
tricity is  now  almost  exclusively  filled  by 
the  metal  lamp.  Data  for  the  costs  of 
400  c.p.  and  50  c.p.  sizes  have  already  been 
given.  For  interior  illumination,  however, 


153 


ELE 


ENCYCLOPEDIA   OF 


ELE 


the  great  majority  of  lamps  are  nowadays 
some  25  c.p.  each.  The  present  market  price 
of  these  lamps  is  about  8s.  per  lamp  as 
against  the  price  of  4s.  per  lamp  of  a 
year  ago.  The  near  future  will  doubtless 
witness  further  material  reductions  in  the 
price  of  metal  lamps.  The  first  cost  is  of 
less  consequence  the  higher  the  price  paid  for 
electricity.  Thus  taking  at  1,000  hours  the 
life  of  a  25  c.p.  metal  lamp,  and  its  consump- 
tion at  1*3  watts  per  c.p.,  the  total  outlay  per 
lamp  per  1,000  hours  of  actual  burning,  for 


times  called  the  Generating  Station,  sometimes 
the  Central  Station,  and  sometimes,  and  prefer- 
ably, the  Electricity  Works.  If  the  area  to  be 
supplied  is  very  limited  in  extent  and  in  the 
immediate  neighbourhood  of  the  Electricity 
Works,  it  may  be  economical  to  employ  sets  in 
which  continuous  electricity  is  generated. 
Almost  all  modern  Electricity  Works  are,  how- 
ever, equipped  with  electric  generators  supply- 
ing polyphase  alternating  electricity.  This 
alternating  electricity  is  transmitted  at  high 
pressure  to  suitably  located  sub-stations,  where 


FIG.  2. — General  Arrangement  of  Power  Station  and  Sub-station. 


varous 
follows  : 


prices   of    electricity,    works  out   as 


.£    . 

X^-i 

r§a 

e  h 

fe  S 

e  a 

°O3 

"§_-» 

ftco 

ft 

ia*3 

01       x 

"?  M° 

"tr  S  <t 

0 

2  SC 

Ct_i  O  "^  C 

c3  cW 

(55  S 

O     P< 

3    •- 

O5"  _S 

•^  ^ 

1  *? 

S  x 

^  5. 

50  — 

•a-fjS 

"3  2" 

£* 

II 

o'SK 

HOJ 

IS 

id. 

3-0 

2-70 

5-7 

0-07 

Zd. 

3-0 

5-40 

8-4 

o-io 

3d. 

3-0 

8-10 

11-1 

0-13 

4d. 

3-0 

10-8 

13-8 

0-17 

5d. 

3-0 

13-5 

16-5 

0-20 

THE  ELECTKICITY  WORKS. — The  building  and 
apparatus  where  a  portion  of  the  energy  of 
the  coal  is  transformed  into  electricity  is  some- 


by  means  of  motor  generators,  it  is  trans- 
formed into  continuous  electricity  and  dis- 
tributed to  the  consumers  in  this  form.  This 
arrangement  is  indicated  diagrammatically  in 
Fig.  2. 

The  coal  is  brought  to  the  electricity  works 
by  canal  or  rail.  In  the  illustration,  the  coal 
is  indicated  as  being  transferred  from  a  canal 
boat  to  a  conveyer,  by  which  it  is  deposited  in 
large  hoppers  at  the  top  of  the  boiler-room.  In 
large  works  these  hoppers  often  have  capacity 
for  5,000  tons  or  more.  The  coal  next  passes 
through  shoots  from  the  hoppers  to  the  auto- 
matic stokers  under  the  boilers,  sometimes 
passing  through  weighing  devices  interposed 
just  before  the  coal  reaches  the  automatic 
stokers.  These  stokers  are  adjustable,  and 


154 


ELE 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


ELE 


deposit  the  coal  uniformly  over  the  grate,  and 
in  the  correct  quantity.  The  correct  adjust- 
ment of  the  supply  of  air  is  no  less  important, 
and  is  attained  by  the  assistance  of  C02 
recorders,  which  should  constitute  part  of 
the  equipment  of  all  Electricity  Works.  The 
boilers  should  be  of  some  one  of  the  several 
excellent  water-tube  types  which  are  now  avail- 
able. These  are  much  more  compact,  and  are 
in  other  respects  more  satisfactory  than  the 
fire-tube  types  formerly  employed.  Even  with 
the  most  compact  boilers,  however,  the  boiler- 
room  necessarily  extends  over  a  considerable 
area.  The  largest  boiler  which  may  at  present 
be  considered  as  thoroughly  standard,  and 
obtainable  from  any  one  of  several  reliable 
manufacturers,  has  a  normal  evaporative 
capacity  for  raising  15  tons  of  steam  per  hour 
"  from  and  at "  100°  C.,  and  can,  when  forced, 
supply  at  the  rate  of  over  20  tons  per  hour 
for  short  periods.  The  superheating  tubes  are 
generally  incorporated  in  the  boiler,  and  may 
be  considered  as  a  component.  Such  a  boiler's 
normal  capacity,  when  supplying  steam  at 
13  atmospheres  and  with  50°  C.  of  superheat, 
which  are  conditions  which  represent  approved 
practice,  and  when  the  feed- water  temperature 
is  50°  C.,  is  only  12*5  tons  of  steam  per  hour, 
since  this  quantity  is  equivalent  to  15  tons 
"from  and  at"  100°  C. 

The  outputs  of  Electricity  Works  are  best 
expressed  in  millions  of  units  (i.e.,  of  kilowatt 
hours)  per  year.  These  outputs  range  from 
one  million  units  per  year  for  the  Electricity 
Works  of  a  small  town,  up  to  100  million 
units  and  more  per  annum  for  Electricity 
Works  in  large  cities.  A  Works  of  the 
latter  size  would  require,  as  an  average, 
some  100  tons  of  steam  per  hour  and 
for  peak  loads  this  would  usually  rise  to 
over  200  tons  per  hour.  Consequently,  in 
order  to  have  sufficient  spare  plant,  at  least 
20  of  the  above  described  boilers  would  be 
required.  These  would  be  arranged  in  groups 
of  four,  and  each  group  would  supply  steam 
to  a  steam  turbine  of  some  8,000  h.p.  capacity. 
There  would  be  five  of  these  steam  turbines, 
and  each  would  drive  a  6,000  kw.  polyphase 


alternator.  All  this  apparatus  would  prefer- 
ably be  arranged  in  five  distinct  groups,  as 
this  gives  additional  certainty  of  absolutely 
uninterrupted  supply.  Each  of  these  groups 
also  comprises  a  surface  condenser.  Outside 
of  the  station  are  located  cooling  towers. 
The  switch  gear  may  be  located  either  at 
one  side  of  the  engine-room  or  in  a  separate 


n 


a 


A  —  Boilers. 

B  —  Turbo-Alternators. 

C  —  Exciters. 


D  —  Switchboard  Gallery. 

E  —  Chimneys. 

F  —  Cooling  Tower. 


FIG.  3. — General  Arrangement  of  Electricity  Works. 

building.  In  modern  plants  the  switch  gear 
is  controlled  by  relays  from  an  operating 
desk.  By  this  means  the  massive  gear  for 
high  pressure  and  large  amounts  of  power 
may  be  perfectly  controlled  by  the  suitable 
manipulation  of  the  low-pressure  relay  circuits. 

The  general  arrangement  of  the  Electricity 
Works  is  indicated  diagrammatically  in 
Fig.  3. 

It  would  exceed  the  limits  of  this  article  to 


155 


ELE 


ENCYCLOPEDIA  OF 


ELE 


enter  upon  the  discussion  of  all  the  machinery 
required  in  an  electricity  works.  Considerable 
interest,  however,  naturally  arises  in  regard 
to  the  significance  to  be  attached  to  the  rating 
ascribed  to  the  electricity  generators.  The 
capacity  stated  on  the  name-plate  of  the  set  is 
of  little  use  in  judging  its  capacity.  Although 
generating  plant  is  always  -sold  to  some  sort 
of  a  specification,  there  is,  as  yet,  no  widely 
acknowledged  standard  basis  of  rating  as 
regards,  for  instance,  temperature  rise  and 
overload.  Thus  we  are  not  learning  much 
when  we  are  informed  that  the  aggregate 
rated  capacity  of  the  generating  sets  in- 
stalled in  any  particular  Works  is  so  many 
kilowatts.  It  has  consequently  come  about 
that  little  or  no  useful  knowledge  is  imparted 
when  it  is  stated  that  the  capital  cost  of  an 
Electricity  Works  is  £25  per  kilowatt  of  plant 
installed.  It  is  rarely  stated  whether  by  the 
kilowatts  capacity  is  meant  the  aggregate 
capacity  of  the  plant  installed  or  only  the 
lesser  capacity  arrived  at  after  deducting  the 
portion  to  be  considered  as  a  reserve.  There 
are  also  the  alternatives  that  the  kilowatts 
capacity  may  be  intended  to  mean  either  the 
average  power  or  the  maximum  power  delivered 
from  the  Works. 

A  suitable  groundwork  on  which  to  prepare 
a  specification  for  the  generating  sets  is  that, 
on  the  basis  of  the  rating  assigned  to  them, 
they  shall  be  capable  of  dealing  with  a  25  % 
overload  for  1  hour,  and  with  a  50  %  over- 
load for  5  minutes  without  detriment  to  any 
part  of  the  steam-electric  set,  and  that  when 
continuously  operated  at  the  rated  output,  no 
accessible  part  of  the  electric  generator  shall 
sustain  a  temperature  rise,  as  thermometri- 
cally  determined,  of  more  than  40°  C.  above 
the  temperature  of  the  engine-room  in  the 
immediate  neighbourhood  of  the  generating 
set. 

There  are  very  many  other  matters,  such 
as  the  steam  consumption,  the  mechanical 
construction,  insulation,  pressure  regulation, 
uniformity  of  angular  rotation,  &c.,  which 
must  be  carefully  stipulated  in  the  detailed 
specification,  but  for  the  purposes  of  the 


broad  outlines  appropriate  to  this  article,  a 
discussion  of  these  details  would  be  out  of 
place. 

The  load  factor  is  the  ratio  of  the  average 
power  delivered  from  the  works  during  the 
entire  8,760  hours  in  the  year,  to  the  maxi- 
mum power  delivered  at  any  time  during 
the  year.  For  a  miscellaneous  load  made  up 
of  lighting,  power,  and  tramways,  the  load 
factor  will  usually  be  not  less  than  25  %  nor 
more  than  40  %.  Under  favourable  conditions, 
when  a  considerable  percentage  of  the  power 
is  required  for  certain  electro-chemical  or 
thermal  processes,  such  as  the  manufacture 
of  calcium  carbide  or  aluminium,  the  resultant 
load  factor  at  the  outgoing  cables  from  the 
Electricity  Works  may  be  even  60%  or  more, 
though  large  miscellaneous  undertakings  with 
a  load  factor  of  even  as  much  as  50  %  are  still 
very  exceptional. 

On  the  basis  of  these  heating  and  overload 
requirements,  an  Electricity  Works  will, 
according  to  the  magnitude  of  its  output, 
require  to  comprise  electricity  generating  sets 
of  the  following  aggregate  rated  capacity  :— 


Rated  Output  of  Station 
in  Megakelvins  per  Year. 


Aggregate  Rated  Capacity  in  kw.  of  Gene- 
rating Sets  Installed,  for  following  Load 
Factors  : 


0-60 


0-40 


0-30 


1-00 

276 

407 

528 

5-00 

1,320 

1,900 

2,470 

20-0 

5,070 

7,500 

9,790 

100- 

24,400 

34,000 

45,200 

In  the  following  table  are  given  representa- 
tive values  for  the  total  cost  of  such  Electricity 
Works  when  built  in  accordance  with  best 
modern  practice. 


Total  Cost  of  Electricity  Supply  Stations, 
Rated  Output  of  Station  in  £,  for  following  Load  Factors  : 

in  Megakelvins  per  Year. 

0-60  0'40  0-30 


1-00 

10,400 

12,500 

13,850 

5-00 

33,700 

46,750 

54,250 

20-0 

95,200 

136,000 

175,000 

100- 

364,000 

505,000 

636,000 

156 


ELE 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


ELE 


In  addition  to  the  capital  outlay  for  the 
Electricity  Works,  there  is  the  capital  outlay 
for  the  conductors  by  which  the  electricity 
is  conveyed  to  the  consumer  and  for  all  the 
works,  such  as  subways  or  towers,  required 
in  the  construction  of  this  transmission  line. 
Usually  also  there  will  be  small  intermediate 
stations,  termed  sub-stations,  in  which  motor 
generators  are  installed,  and  where  the  elec- 
tricity which  has  been  transmitted  at  the 
high  pressure  required  in  the  interests  of  low 
outlay  for  conductors,  is  transformed  into 
electricity  at  the  low  pressure  desired  by 
the  consumer.  The  costs  of  the  system 
between  the  Electricity  Works  and  the  con- 
sumer's premises  vary  widely  according  to 
the  distance,  the  number  and  distribution 
of  the  consumers,  the  amount  of  electricity 
required  by  the  consumers  individually  and 
collectively,  the  extent  to  which  the  times 
during  which  the  various  consumers'  require- 
ments for  electricity  overlap  with  one  another, 
and  on  several  other  conditions.  In  general, 
these  costs  will  aggregate  from  one-half  of  the 
cost  of  the  electricity  works  up  to,  and  some 
times  even  in  excess  of,  the  cost  of  the  Elec- 
tricity Works. 

The  aggregate  of  the  capital  and  depre- 
ciation costs  of  the  Electricity  Works  and 
of  the  distribution  system,  which  may  be 
termed  the  capital  costs,  taken  together 
with  the  operating  costs,  lead  to  a  cost  per 
unit  delivered  at  the  consumer's  premises, 
which,  averaged  for  all  the  consumers, 
may,  with  coal  at  10s.  per  ton,  and  with  a 
load  factor  of  35  %,  so  far  as  concerns 
the  general  order  of  magnitude,  be  taken 
as  requiring  the  following  average  price 
per  unit :— 


Annual  Output  from  Electricity  Works 
in  Units  (i.e.,  Kilowatt  Hours 
per  Annum). 

Average  Price  in  Pence 
per  Unit. 

5,000,000 

1-3 

10,000,000 

1-0 

20,000,000 

0-70 

50,000,000 

0-60 

100,000,000 

0-55 

Estimates  indicating  lower  average  prices 
are  sometimes  seen,  and  the  results  are,  from 
their  very  nature,  greatly  dependent  upon 
very  many  special  circumstances  of  each  ease, 
such  as  the  terms  on  which  capital  may  be 
obtained,  facilities  for  obtaining  ample  and 
cool  condensing  water  at  a  low  price,  accessi- 
bility to  rail  or  water-ways  as  affecting  not 
only  the  price  of  fuel  but  also  the  price  of 
machinery  as  delivered  on  the  site,  wages, 
intelligence  and  disposition  of  employees, 
enterprise  and  knowledge  on  the  part  of  the 
management ;  nature,  extent,  and  geographical 
distribution  of  the  industries  in  the  region, 
and  on  various  other  conditions. 

It  should  not  be  concluded  that  all  con- 
sumers will  pay  this  average  price.  On  the 
contrary,  an  equitable  distribution  of  the 
charges  allocates  to  certain  consumers  a  price 
of  two  or  three  times  the  average  price, 
while  the  supply  to  other  consumers  is 
profitable,  even  at  half  or  less  of  the  average 
price. 

The  equitable  price  to  any  particular  con- 
sumer will  be  less — 

1.  The  less  the  distance  to  which  his  elec- 
tricity must  be  transmitted. 

'2.  The  greater  the  number  of  consumers 
who  can  be  supplied  over  the  same  conducting 
system. 

3.  The    less     the    extent    to    which     the 
consumer's   load  overlaps  the  load  of   other 
consumers. 

4.  The  greater  the  amount  he  consumes  per 
annum. 

5.  The  greater  the  annual  load  purchased 
from  the  Electricity  Works  by  the  consumers 
collectively. 

6.  The    higher     the    load    factor    of    this 
aggregate  load. 

7.  The    higher    the    load     factor    of     the 
consumer's  own  load. 

Many  other  conditions  must  also  be  taken 
into  account.  Thus,  if  the  consumer  requires 
electricity  in  the  same  form  and  at  the  same 
pressure  as  that  at  the  outgoing  cables  from 
the  Electricity  Works,  he  will  pay  a  much 
lower  price  than  if  he  requires  the  electricity 


157 


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ENCYCLOPEDIA   OF 


ELE 


transformed  in  pressure  or  in  kind,  or  in  both 
respects. 

SYSTEMS  OF  CHARGING  FOR   ELECTRICITY.— 
There  are   numerous  methods  whereby  eon- 


FIG.  4. — Section  of  Typical  Meter. 

sumers  are  charged,  but  the  following  methods 
are  the  more  common  ones  : — 

(1.)  Flat   rate.     This  method  requires  the 
consumer  to  pay  a  constant  price  per  unit, 
irrespective  of  his  load  factor.     For  private 
lighting  this  rate   generally  lies   between 
Sd.  and  6d.  per  unit,  and  for  power  the 
limits  are  generally  of   the   order   of   Id. 
and  2d.  per  unit. 

(2.)  Fixed  minimum  consumption  rate. 
This   method   requires    the    consumer    to 
pay  a  certain  sum  each  year  irrespective 
of  his  load,  in  addition  to  a  certain  price 
per  unit  for  each  unit  consumed.      This 
system  is  generally  used  for  private  light- 
ing,  when   there   is    only  one    customer, 
or  perhaps  a  few,  being  supplied  over  a 
long  and  otherwise  "dead"  main.     It  is 
a  fairly   representative  method,   however, 
of  charging  for  electricity  used  for  power 
purposes.     This  system  is  very  similar  to 
the  "Manchester  system"  introduced  by  Dr. 
Hopkinson.      The  price   charged  under  this 
system   was   made   to   depend   upon  a   fixed 
rental  plus  a  proportional  charge  for  energy, 
the    fixed    rental   being    determined   by   the 


number  of  8  c.p.  lamps,  or  the  equivalent 
thereof,  wired. 

(3.)  Maximum  demand  rate.  This  is  some- 
times called  the  "  Wright  system,"  or 
"  Brighton  system."  This  rate  charges  a 
high  price  (generally  Id.  or  8d.)  per  unit 
for  a  consumption  equivalent  to  the  use 
of  the  maximum  demand  for  a  certain  time 
(generally  1  hour  per  day),  and  a  low  price 
(generally  between  2<Z.  and  4d.)  per  unit  for 
any  energy  consumed  beyond  this  amount. 
In  this  system  a  "  maximum  demand  indi- 
cator "  is  introduced  into  the  consumer's 
circuit.  For  an  example,  suppose  the  con- 
sumer's quarterly  (say  90  days)  consumption 
is  1,500  units,  and  the  indicator  shows  a 
maximum  demand  of  10  kilowatts,  there  will 
be  10  X  90  =  900  units  to  be  charged  at  the 
high  rate  (Id.  or  Sd.),  and  only  1,500  —  900 
=  600  units  to  be  charged  at  the  low  rate 
(<2d.  to  4d.). 

(4.)  Sliding  scale  rate.  The  customer  is 
required  to  pay  a  net  flat  rate  for  the  first 
1,000  units  (or  other  quantity)  consumed  per 
quarter.  For  each  successive  1,000  units 
an  increasing  discount  is  made  from  the 
flat  rate  up  to  a  certain  total  consumption, 


FIG.  5. — Diagram  showing  Wiring  of  the  "Adnil" 
One-meter  System  for  Lighting  and  Power  Circuits. 

after    which    the     price    per    unit    remains 
constant. 

ELECTRICITY  METERS. — It  is  not  sufficient 
for  a  consumer  of  electricity  to  be  acquainted 
only  with  the  current  and  pressure  which  he 


158 


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MUNICIPAL   AND    SANITAEY  ENGINEERING. 


ELE 


may  be  using,  but  he  must  also  be  able  to 
ascertain  the  total  energy  delivered  to  him, 
irrespective  of  the  current  and  pressure  at  any 
particular  time.  An  instrument  capable  of 
measuring  this  energy  is  termed  an  "  electricity 
meter."  A  rough  classification  of  electricity 
meters  is  afforded  by  the  nature  of  the  circuit 
on  which  they  are  intended  to  be  employed. 
Thus  there  are  those  that  can  be  employed  on 

1.  Continuous  electricity  circuits  only; 

2.  Alternating  electricity  circuits  only  ; 

3.  Both    continuous  and  alternating  elec- 
tricity circuits. 

They  may  again  be  classed  as 

1.  Motor  meters, 

2.  Clock  meters,    and 

3.  Electrolytic  meters. 

All  three  of  these  types  are  extensively  used. 
Practically  all  modern  meters  are  of  the  watt 
hour  type,  frequently  called  integrating 
or  recording  watt  meters.    These  register 
the  use  of   electricity  in  watt  hours  by 
means  of  dials  and  pointers.    Sometimes 
these  dials  are  arranged  to  read  directly 
in  units  (1,000  watt  hours),   and  parts 
and    multiples    of   units.      Each  dial  is 
divided    into     ten    divisions,    and    one 
revolution  of  the  pointer  of  any  dial  is 
equal  to  one  division  of  the  dial  of  next 
greater  value.     The  dials  are  most  con- 
veniently  and   accurately    read    in    the 
order   beginning    with   that    having  the 
lowest   capacity,   and   in   recording   the 
reading,  the  result  should   be   written   from 
right   to   left.     In  Fig.  6  are  given  several 
dials  which  will  serve  as  an  illustration   in 
reading.     In  this  case  the  reading  is  8839'5 
Board  of  Trade  units.    The  accuracy  of  meters 
generally  lies  between  1  and  2  °/0  slow  or  fast. 
Three  per  cent,   either   side   should  be  con- 
sidered the  maximum  allowable. 

A  type  of  electricity  meter  which  has  come 
extensively  into  use,  especially  with  small 
consumers,  is  the  "  prepayment  meter."  With 
this  meter  the  consumer  cannot  possibly  use 
more  light  than  he  pays  for,  and  since  he  has 
to  pay  for  the  light  before  he  obtains  it,  he 
does  not  incur  any  liabilities  in  this  respect. 


TRANSFORMING  STATIONS  AND  APPARATUS. — 
The  electricity,  when  it  is  sent  out  from  the 
Electricity  Works,  is  usually  of  a  pressure 
unsuitably  high  for  the  consumer's  purposes. 
Very  often  also,  the  consumer's  electrical 
apparatus  requires  to  be  supplied  with  elec- 
tricity of  some  other  commercial  variety  than 
that  in  which  it  is  sent  out  from  the  Electricity 
Works.  The  commercial  names  for  the  lead- 
ing forms  of  electricity  are 

I.  Continuous  electricity,  and 

II.  Alternating  electricity. 

This  second  form  may  again  be  sub-divided 
into 

Ila.  Polyphase  electricity,  and 

lib.  Single  phase  electricity. 

It  is  in  the  form  Ila,  i.e.  polyphase  elec- 
tricity, that  the  energy  is  usually  sent  out 
from  the  Electricity  Works.  As  sent  out  from 


£>oarcf  o     Trade  i/n/6s 


IOOO 


Diriuon 


FlG.  6. — Arrangement  of  Dials  on  an  Electricity  Meter. 

the  Works  the  electricity  is  of  high  pressure. 
If  the  consumer  requires  his  electricity  in  this 
same  form  but  at  lower  pressure,  the  change 
is  effected  by  interposing  a  so-called  stationary 
transformer. 

Such  a  piece  of  apparatus  is,  in  principle, 
a  laminated  iron  structure  on  which  are 
wound  two  coils,  one  of  which,  termed  the 
primary,  is  connected  to  the  high  pressure 
circuit,  the  other,  termed  the  secondary,  being 
connected  to  the  low  pressure  circuit,  i.e.  to 
the  circuit  on  the  consumer's  premises. 
Stationary  transformers  also  suffice  for  obtain- 
ing a  single  phase  supply  from  a  polyphase 
circuit.  Thus,  when  it  is  required  to  simply 


159 


ELE 


ENCYCLOPAEDIA   OF 


ELE 


change  the  pressure  of  alternating  electricity, 
a  stationary  transformer  suffices.  In  this 
type  of  apparatus  the  transformation  is  effected 
at  an  efficiency  of  some  90  to  98  %,  accord- 
ing to  the  size,  periodicity,  and  pressures. 

Very  often,  however,  the  required  trans- 
formation is  from  the  high  pressure  polyphase 
electricity  supplied  from  the  Electricity  Works, 
into  low  pressure  continuous  electricity ;  in 
fact,  in  the  majority  of  cases,  the  low  pressure 
circuits,  whether  for  lighting  or  for  power,  are 
designed  for  continuous  electricity. 

To  effect  a  transformation  of  energy  from 
any  form  of  alternating  electricity  into  con- 
tinuous electricity,  rotating  apparatus  is 
required.  The  transformation  is  usually 
effected  on  a  large  scale  in  apparatus  located 
in  so-called  sub-stations.  The  most  suitable 
apparatus  for  the  purpose  is  a  motor  generator. 
The  motor  receives  the  electricity  to  be  trans- 
formed and  converts  it  into  mechanical  energy, 
which  serves  to  drive  the  electric  generator  in 
which  it  again  becomes  transformed  into  elec- 
trical energy.  This  electrical  energy  is  in  the 
continuous  form  and  of  the  pressure  required 
by  the  consumer.  The  transformation  is,  in 
the  customary  sizes,  effected  with  an  efficiency 
of  some  85  to  90  %. 

There  is  a  device  termed  a  rotary  converter 
which  is  often  put  forward  for  such  work. 
It  is,  however,  as  regards  adjustability  and 
convenience  of  operation,  distinctly  inferior  to 
the  motor  generator.  It  has  slightly  higher 
efficiency,  and  is  also  cheaper,  but  its 
superiority  in  these  respects  is  more  than 
offset  by  its  inferior  operating  characteristics. 
The  same  verdict  applies  to  the  so-called 
motor  converter  which  is  a  compromise  between 
the  motor  generator  and  the  rotary  converter. 

ELECTRIC  MOTORS. — The  most  suitable  type 
of  electric  motor  can,  in  any  particular  case, 
only  be  determined  upon  by  careful  considera- 
tion of  the  work  required  of  it.  The  two 
chief  classes  are 

1.  Continuous  motors. 

2.  Alternating  motors. 

1.  CONTINUOUS  MOTORS. — Where  a  variable 
speed  is  required,  continuous  motors  are  pre- 


ferable, as  any  desired  range  of  speed  may 
be  provided  by  suitably  designed  continuous 
motors.  Exceedingly  fine  speed  adjustments 
may  also  be  obtained  with  these  motors. 
Continuous  motors  may  be  divided  into  two 
broad  classes : 

a.  Series  wound  motors. 

b.  Shunt  wound  motors. 

Series  wound  motors  are  usually  employed 
for  work  where  a  high  starting  torque  is 
desired,  and  where  the  motors  are  started  and 
stopped  at  frequent  intervals.  They  are  almost 
invariably  employed  for  tramcars  and  for 
electric  propulsion  in  general.  Series  motors 
are  not  suitable  where  constant  speed  is 
desired  at  varying  loads,  since  the  speed  of 
the  motor  decreases  greatly  with  increasing 
load. 

Shunt  motors  should  be  supplied  for  cases 
where  it  is  desired  to  obtain  constant  speed 
independently  of  load  variations.  This  speed 
can  be  altered  to  any  one  of  a  wide  range  of 
values  by  simple  adjustment  of  the  excitation. 
After  the  excitation  has  been  once  adjusted, 
the  speed  remains  constant  for  all  loads  until 
the  excitation  is  readjusted  for  some  other 
desired  speed.  This  process  is  termed  "  speed 
variation  by  shunt  control." 

2.  ALTERNATING  MOTORS. — These  are  usually 
of  the  polyphase  type  and  have  the  character- 
istic that,  except  for  types  of  complicated 
construction,  they  can  only  be  run  efficiently 
at  some  one  particular  speed.  This  restricts 
their  use  to  a  certain  extent,  but  for  industrial 
processes  it  constitutes  a  valuable  property. 

The  most  hardy  form  of  polyphase  motor 
is  that  commonly  called  a  squirrel-cage  motor, 
for  the  reason  that  the  conducting  system 
carried  by  the  rotating  member  bears  some 
resemblance  to  a  squirrel-cage.  In  this  type 
of  motor  there  are  no  moving  contacts,  and 
consequently  there  is  a  minimum  of  likelihood 
of  anything  getting  out  of  order.  On  the 
other  hand,  this  type  of  motor  has  but  slight 
starting  torque,  or  when  arranged  for  develop- 
ing any  considerable  amount  of  starting 
torque  it  is  necessary  to  consume,  during  the 
process  of  starting,  a  very  large  current.  The 


160 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


ELE 


motor  is  so  hardy  as  to  be  absolutely  unharmed 
by  these  large  but  temporary  currents.  On 
the  other  hand,  these  currents  interfere  with 
the  maintenance  of  good  pressure  regulation 
on  the  supply  mains,  and  are  thus  harmful 
where  lights  are  supplied  from  the  same 
circuits.  If  the  supply  mains  are  liberally 
designed,  there  should  be  no  objection  to  the 
use  of  squirrel-cage  motors  of  not  over 
5  h.p.  capacity,  even  when  required  to  develop, 
at  starting,  one-third  of  their  full  load  torque. 
Much  larger  squirrel-cage  motors  may  also  be 
permitted,  provided  they  may  be  started  up 
without  load. 

When  high  starting  torque  with  only 
moderate  current  consumption  is  required, 
polyphase  motors  of  the  slip  ring  type 
should  be  employed  instead  of  squirrel- 
cage  motors.  With  these  slip  ring  alter- 
nating motors,  equally  good  starting  torque 
may  be  obtained  as  with  continuous  motors. 
With  the  slip  ring  type  it  is  also  prac- 
ticable, by  the  use  of  an  external  rheostat, 
to  obtain  any  desired  speed,  but  only  at 
very  low  efficiency. 

There  is  another  class  of  alternating  motor 
termed  the  single  phase  motor.  When  a  vari- 
able speed  motor  is  required  on  premises  where 
the  supply  is  alternating  electricity,  a  single 
phase  commutator  motor  should  be  employed. 
For  work  where  the  speed  may  vary  with  the 
load,  such  motors  are  available  up  to  several 
hundred  h.p.  capacity,  but  the  types  of  single 
phase  commutator  motor  suitable  for  con- 
stant speed  with  varying  load,  are  only 
satisfactory  in  very  small  sizes.  All 
single  phase  motors  are  very  large  and 
expensive  for  their  output,  and  they  have 
relatively  low  efficiency  as  compared  with 
continuous  motors  and  polyphase  alternating 
motors. 

Series  wound  single  phase  commutator 
motors  have  for  several  years  been  employed 
for  traction,  but  with  indifferent  results. 
The  chief  drawback  is  that  the  equipment 
is  far  heavier  and  more  expensive  than 
the  equivalent  equipment  with  continuous 
motors.  H.  M.  H. 


Electrolysis,  Purification  by. — Purifi- 
cation of  water  or  sewage  by  direct  electrolysis 
has  been  a  failure  in  practice,  mainly  because 
a  great  part  of  the  liquid  passed  nearly  or 
quite  unaltered  between  the  electrodes.  In 
an  indirect  process,  the  Hermite,  sea  water  is 
electrolysed  and  added  to  sewage  or  used  for 
flushing.  The  fluid  acted  in  most  cases  as  a 
solution  of  hypochlorous  acid  (see  "  Chloride 
of  Lime"),  and  its  standard  strength  was 
0'05  %  of  available  chlorine.  A  cause  of  failure 
was  that  the  solid  lumps  in  raw  sewage  were 
so  difficult  of  penetration.  By  the  electro- 
lysis of  brine  containing  2  %  or  3  %  of  NaCl, 
Woolf  prepared  "  Electrozone,"  which  was 
employed  on  the  effluent  at  Maidenhead,  but 
afterwards  abandoned ;  it  was  later  used  with 
hygienic  success  at  Havana,  Cuba.  Difficulties 
have  been  the  expenditure  of  power  in  pro- 
portion to  the  result  and  the  rapid  spoiling 
of  the  solutions.  A  stronger  liquid  is  now 
manufactured  from  brine  by  the  "  Oxy- 
chlorides  "  Company  in  a  special  electrolyser 
which  claims  several  economic  advantages, 
while  by  certain  additions  the  properties  of 
the  fluid  are  made  more  lasting.  Its  use  is 
still  being  tried  at  the  Guildford  Sewage  Works, 
and  has  recently  been  examined  there  by  the 
writer,  and  also  by  the  Sewage  Commission. 
Raw  sewages  from  this  and  other  places,  and 
effluents  from  septic  tanks  and  primary, 
secondary,  and  tertiary  filters,  were  treated 
with  the  solution  under  varying  conditions  to 
ascertain  its  efficiency  as  dealing  with  putre- 
factive and  pathogenic  organisms  and  with 
suspended  matter  which  might  cause  sub- 
sequent trouble.  The  experiments  showed,  in 
common  with  the  results  of  other  investigators, 
that  the  germicidal  power  of  these  solutions 
was  exerted  almost  immediately,  and  was 
greater  than  the  chemical  measure  of  their 
"available  chlorine"  content,  but  that  the 
latter  was  very  rapidly  reduced  by  organic 
matters  present,  whereas  it  was  advisable  for 
a  small  margin  to  be  left  for  a  slightly  longer 
continued  action,  in  which  the  active  chlorine 
would  disappear.  For  efficiency  the  chlorous 
solution  is  therefore  applied  quantitatively, 


M.S.E. 


161 


ELE 


ENCYCLOPEDIA   OF 


EST 


and  for  economy  the  organic  matter  should 
be  previously  reduced  by  ordinary  sewage 
treatment,  the  electrolysed  solution  being 
used  as  a  "  finisher."  In  the  strong  raw 
sewage  at  Guildford  the  total  organisms  were 
reduced  by  3  parts  per  100,000  of  available 
chlorine  from  several  millions  to  50,000,  by 
5  parts  to  20,  and  by  7  parts  to  10  per  c.c. 
With  3'7  parts  available  chlorine  the  reduction 
was  :  coli  organisms  from  over  one  million  to 
none  found  in  1  c.c. ;  enteritidis  spores  from  over 
1,000  to  less  than  10;  total  organisms  from  23 
millions  to  240  per  c.c.  Average  weaker  sewages 
gave  similar  results  with  less  of  the  solution, 
and  within  limits  a  longer  period  of  treatment 
also  allowed  of  a  lower  available  chlorine. 
The  sludge  was  less,  and  when  spread  on  land 
remained  sweeter  than  with  ordinary  chemical 
treatment.  It  was  found  that  in  these  pol- 
luted liquids  about  60%  of  the  available  chlorine 
was  almost  at  once  taken  up  by  the  organic 
matters,  while  the  remainder  acted  immedi- 
ately on  the  bacteria  and  more  slowly  on  the 
resistant  impurities.  In  septic  tank  liquors 
with  2£  to  4£  parts  of  available  chlorine  and  1 
to  4  hours  contact,  an  original  content  of  2^  to 
4^  million  total  organisms,  100,000  to  a  mil- 
lion coli,  and  10  to  1,000  enteritidis  spores 
per  c.c.,  became  20  to  600  total,  with  coli 
and  enteritidis  absent  from  1,  and  in  most 
cases  from  5  c.c.,  while  the  incubation  and 
dissolved  oxygen  tests  were  also  rendered 
satisfactory.  With  good  effluents  sterility, 
except  as  regards  a  few  organisms  of  the  hay- 
bacillus  type,  which  are  useful  in  the  further 
breaking  down  of  organic  matter,  was  ensured 
by  5  parts  per  100,000  of  available  chlorine,  and 
removal  of  coli  and  enteritidis  by  0*5  or  even 
0'25  part,  in  2  to  4  hours.  Mixing  and  proper 
time  are  attained  by  running  through  a  con- 
duit with  baffle  plates  or  cascades ;  the  effluent 
at  the  outfall  should  show  a  faint  blue  tint 
with  iodide  of  potassium  and  starch.  The 
solution  also  proved  effective  against  the 
growth  of  alga3  and  fungi  in  waters,  and  in 
the  treatment  of  a  tap  water  for  conferva  the 
only  chemical  alteration  was  an  increase  of 
the  chlorine  from  2'1  to  2'4  parts  Cl  per 


100,000  and  a  decrease  of  the  "oxygen  con- 
sumed." The  Royal  Commission  on  Sewage 
found  at  Guildford  that  a  small  quantity  of 
the  liquid  rendered  septic  tank  effluents  in- 
offensive, and  that  "  a  dose  of  oxychloride 
more  than  sufficient  to  remove  smell  and  kill 
coli  did  not  prejudice  the  purifying  ability  of 
filters."  The  above  results  as  to  conditions 
for  practical  sterilisation  have  been  since 
confirmed  by  Phelps  and  Carpenter  at  the 
Massachusetts  Station,1  who  consider  that 
electrolytic  chlorine  is  cheaper  and  probably 
more  efficient  than  chloride  of  lime,  and  by 
Kellerman  and  others  for  the  U.S.  Depart- 
ment of  Agriculture.3  (See  also  "  OZONE, 
PURIFICATION  OF  WATER  BY.")  S.  R. 

Enteric  Fever.— (See  "  TYPHOID  FEVER.") 

Estimating  (General  Engineering).— 

The  methods  by  which  the  cost  of  engineering 
work  may  be  arrived  at  vary  somewhat  with 
the  class  of  the  job,  and  also  with  the  purpose 
of  the  estimate.  If,  for  instance,  a  municipal 
engineer  wishes  to  count  the  cost  of  a  pro- 
posed undertaking,  which,  if  proceeded  with, 
will  be  executed  by  a  contractor,  he  will 
chiefly  be  concerned  with  the  price  to  be  paid, 
not  with  the  actual  cost  of  the  work  to  the 
contractor  or  manufacturer.  If,  on  the  other 
hand,  the  work  is  to  be  carried  out  by  his  own 
staff,  he  will  require  to  ascertain  the  probable 
cost  of  production.  In  the  first  case  the 
engineer  will  be  in  the  position  of  a  buyer, 
and  will,  therefore,  acquaint  himself  with  the 
market  values  of  the  various  classes  of 
material  and  workmanship  contained  in  his 
scheme.  Supposing,  however,  that  he  intends 
to  carry  out  the  work  himself,  he  is  then 
somewhat  in  the  position  of  a  contractor, 
except  that  he  will  not  be  embarrassed  with 
the  difficult  question  of  profit.  The  latter 
depends  upon  the  nature  of  the  work,  the 
state  of  trade,  competition,  the  reputation  of 
the  contractor,  and  other  factors.  To  properly 


1  "  Techn.  Quarterly,"  1906. 

2  Bulletin  115,  Oct.,  1907. 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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weigh  such  considerations  requires  a  know- 
ledge of,  and  a  talent  for,  business,  that  can 
only  be  gained  by  experience,  coupled  with  an 
aptitude  which  is  more  or  less  a  gift.  From 
what  has  been  said  it  will  be  evident  that  two 
principles  are  involved  in  an  engineering 
estimate — the  technical  and  the  commercial. 
The  technical  work  consists  in  calculating  the 
quantity  and  frequently  the  weight  of  the 
material,  and  estimating  the  amount  of  labour 
required,  whilst  the  pricing  of  the  material 
and  labour,  and  the  addition  of  a  proper  sum 
for  working  expenses,  contingencies,  and 
profit,  constitute  the  commercial  element. 
The  materials  employed  by  engineers  are 
numerous  and  varied,  but  the  methods  used 
to  determine  their  extent  are  much  the  same 
in  all  cases,  and  consist  in  the  practical  appli- 
cation of  the  rules  of  mensuration.  With 
some  materials,  such  as  metals,  a  further 
calculation  is  made  to  ascertain  their  weight, 
whilst  with  others  this  is  unnecessary,  as 
their  price  is  based  upon  the  cubical  con- 
tents and  sometimes  their  superficial  area. 
Obviously,  many  articles  will  be  purchased 
in  a  finished  state.  The  estimation  of  work- 
manship is  far  more  difficult  and  needs 
experience  and  judgment.  Cost  sheets  of 
similar  jobs,  when  available,  should  always  be 
studied,  but  the  information  derived  therefrom 
must  be  applied  with  discretion,  as  the  con- 
ditions may  not  be  the  same,  especially  after 
a  lapse  of  time.  Certain  articles  of  manu- 
facture, castings  and  forgings  for  instance, 
are  so  regularly  and  repeatedly  produced  that 
a  rate,  varying  with  the  class  of  the  work,  can 
be  charged,  which  will  cover  both  material  and 
workmanship.  In  this  case  it  is,  of  course, 
only  necessary  to  calculate  the  weight  of  the 
article — whether  it  is  produced  on  the  premises 
or  bought  outside.  The  number  of  foremen, 
shop  labourers,  and  others  indirectly  engaged 
upon  the  work,  bears  a  fairly  constant  relation 
to  the  number  of  craftsmen,  so  that,  except 
in  special  jobs  requiring  extra  supervision  or 
assistance,  their  wages  are  not  directly 
charged,  but  added  in  the  form  of  a  percen- 
tage, usually  upon  the  skilled  labour.  Two 


systems  of  pricing  materials  and  workmanship 
are  in  vogue  ;  the  simpler  and  more  usual 
plan  is  to  charge  them  at  rates  which  will 
cover  working  expenses  and  include  profit,  the 
resulting  estimate  representing  the  probable 
cost  to  the  buyer.  The  other  system  is  to  rate 
the  material  at  its  actual  cost  to  the  manu- 
facturer, and  to  debit  each  item  of  workman- 
ship with  the  wages  that  it  is  estimated,  will 
be  paid,  plus  a  percentage  to  cover  working 
expenses.  In  this  way,  the  probable  actual 
cost  to  the  manufacturer  or  contractor  is 
arrived  at,  leaving  him  free  to  add  a  sum  for 
contingencies  if  the  work  is  of  a  nature  to 
require  it,  and  whatever  amount  of  profit  he 
may  desire,  or  consider  advisable.  This  is 
certainly  a  more  exact  method  than  the  other, 
and  has  many  advantages ;  for  one  thing  it 
enables  a  close  comparison  to  be  made  between 
the  estimated  and  the  actual  cost  of  the  work. 
The  question  of  working  expenses  is  a  most 
important  one,  as  in  some  branches  of 
engineering,  e.g.,  a  machine  shop,  they  amount 
to  as  much,  or  even  more,  than  the  wages 
paid  to  the  skilled  men.  Working  or  indirect 
expenses  may  be  said  to  consist  of  those  items 
which  it  is  not  practicable  to  charge  directly 
to  the  customers,  such  as  rent,  rates,  fuel, 
wages  of  unskilled  labour,  supervision  and 
management,  interest  on  capital,  repairs, 
insurance,  and  the  many  other  expenses 
incurred  in  carrying  on  the  work  of  an  estab- 
lishment. They  may  be  arrived  at  by  dividing 
the  total  expenditure  over  a  given  period 
under  three  heads,  viz.,  materials  charged  to 
jobs,  wages  ditto,  the  remainder  representing 
indirect  expenses.  The  ratio  that  the  last 
will  bear  to  the  direct  expenditure  will  vary 
with  the  nature  of  the  work  carried  on,  and 
therefore  will  not  be  the  same  for  each 
department;  further,  it  will  alter  from  time  to 
time,  according  to  the  state  of  trade.  The 
percentage  representing  indirect  expenses 
might  be  applied  to  material,  wages,  or  both. 
As  wages  are  not  liable  to  such  fluctuations 
as  material,  and  for  the  reason  that  many 
items  of  indirect  expenditure  will  vary  with 
the  number  of  skilled  workmen  employed,  a 


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percentage  based  upon  the  wages  of  the  latter 
will  generally  bear  a  more  constant  relation 
than  one  upon  material,  and  is  in  consequence 
usually  to  be  preferred.  This  point  is,  how- 
ever, largely  decided  by  the  nature  of  the 
business.  As  previously  mentioned,  some 
departments  are  more  expensive  to  run  than 
others ;  to  arrive  at  a  correct  distribution 
involves  a  careful  division  of  the  aggregate 
expenses  into  those  which  are  special  to  each 
department  and  common  to  all.  If  the  special 
expenses  are  allotted  to  the  departments 
incurring  them,  and  the  common  expenses 
are  spread  over  the  departments  in  proportion 
to  the  skilled  wages  paid  in  each,  a  practically 
correct  distribution  should  be  effected. 

E.  L.  B. 

Ferozone,  or  magnetic  ferrous  carbon 
(see  "  INTERNATIONAL  PROCESS  OF  SEWAGE 
PURIFICATION  ")• — This  material  is  obtained 
from  the  same  mineral  that  forms  the  basis 
of  "  polarite  "  (see  "  POLARITE  "),  but  is  treated 
in  a  different  way.  Ferozone  is  rich  in  ferrous 
iron,  and  alum,  calcium,  sulphate  of  magnesia, 
and  rustless  magnetic  oxide  of  iron  are 
amongst  its  constituents.  The  object  of  the 
"  ferozone  "  is  to  act  as  a  precipitant  and  to 
assist  in  the  disinfection  and  deodorisation 
of  the  sewage  and  sludge. 


Ferrometer. — (See 
OF  IRON  PROCESS.") 


CONDER'S    SULPHATE 


Filtering  Head. — (See  "FILTRATION.") 

Filters,  Domestic. — Filters  may  be  used 
in  domestic  practice  for  removing  visible 
suspended  matter,  for  arresting  microscopic 
organisms  such  as  bacteria,  and  for  modifying 
the  chemical  composition  of  the  water  itself. 
From  the  sanitary  standpoint  the  effect  of  a 
filter  on  the  chemical  composition  of  a  natural 
water  is  of  no  practical  importance.  Apart 
from  injurious  metals,  such  as  lead,  and  from 
excessive  quantities  of  such  salts  as  calcium 
carbonate,  on  which  filtration  exerts  only  a 
trifling  effect,  it  is  questionable  whether  any 


chemical  constituents  even  of  polluted  waters 
in  the  quantities  in  which  they  can  occur 
naturally  have  any  physiological  effect  at  all. 
There  is  certainly  no  evidence  whatever  that 
water  which  has  been  subjected  to  such 
chemical  modification  as  can  be  produced  by 
a  filter  is  in  any  respect  more  wholesome  or 
less  dangerous  than  the  same  water  before  it 
has  undergone  such  chemical  treatment.  Few 
domestic  filters  do  more  than  remove  suspended 
matter.  They  generally  allow  the  passage  of 
bacteria  through  the  filter-mass  into  the  fil- 
trate. If  a  water  which  has  been  infected  even 
slightly  and  temporarily  is  passed  through 
such  a  filter,  some  of  the  infective  bacteria 
will  be  arrested  in  the  favourable  breeding 
ground  provided  in  the  filter  pores,  and  may 
multiply  there  for  very  long  periods,  causing 
enormous  increase  in  the  extent  of  infection 
of  any  further  water  which  may  pass  through 
it,  or  polluting  dangerously  a  fresh  supply  of 
water  which  before  filtration  may  be  quite 
pure.  Accordingly  the  ordinary  chemical 
filter,  whether  of  carbon  (animal  or  vegetable 
charcoal,  plain,  "  silicated,"or  "manganous  "), 
sponge,  felt,  iron  (spongy  or  magnetic),  or 
equivalent  materials  must  be  condemned  as 
able  to  produce  grave  danger  and  wholly 
incapable  of  affording  any  real  protection  to 
health.  When  used  for  the  removal  of  visible 
suspended  matter  any  suspicious  water  passed 
through  them  must  be  treated  so  as  to  destroy 
or  remove  any  disease  bacteria  which  it  may 
contain.  The  removal  of  bacteria  from  water 
by  filters  depends  on  some  surface  action 
which  is  not  thoroughly  understood.  It  is 
not  merely  a  straining  such  as  occurs  in  the 
removal  of  visible  suspended  matter,  for 
bacteria  will  be  arrested  in  pores  much  larger 
than  themselves.  Bacteria  so  arrested  may 
find  their  way  ultimately  into,  the  filtered 
water  if  the  conditions  are  such  as  to  allow 
this.  This  passage  of  bacteria  through  the 
pores  is  not  caused  by  mere  pressure  of  water, 
and  is  probably  due  to  the  growth  of  the 
bacteria  in  the  pores  of  the  filter  under  the 
influence  of  substances  favourable  to  their 
development.  The  extent  to  which  this 


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growth  occurs  depends  on  the  nature  of  the 
bacteria.  Those  which  are  normal  inhabit- 
ants of  water,  and,  therefore,  develop  at  low 
temperatures  upon  substances  such  as  are 
contained  in  water,  will  grow  through  the 
pores  of  a  filter,  when  bacteria  which  cause 
disease  in  man  and  grow  normally  at  higher 
temperatures  and  upon  media  not  found  in 
water  may  fail  to  penetrate.  Of  bacterial 
filters  the  Pasteur  (Chamberland)  is  the  best 
known.  Laboratory  evidence  has  shown  that 
it  arrests  any  pathogenic  bacteria  contained 
in  drinking  water,  and,  what  is  still  more 


applied  direct  to  the  main,  the  filtrate  being 
collected  in  a  suitable  reservoir.  The  filter 
is  thus  kept  constantly  charged  and  omissions 
to  fill  it  avoided.  A  filter  should  be  chosen 
of  larger  initial  output  than  what  will  be 
actually  drunk,  as  there  is  some  decrease  in 
output  through  use,  the  extent  varying  with 
the  nature  (not  necessarily  with  the  bac- 
teriological quality)  of  the  water.  W.  P. 

Filter-Presses  for  Sewage  Sludge.— 

Of  the  various  methods  for  dealing  with 
sewage  sludge,  that  of  forming  it  under 


"  Dehne"  Sludge  Press,  by  Harzer  &  Co. 


important,  the  filter  has  been  used  widely 
under  conditions  permitting  accurate  record 
of  the  effect  on  waterborne  disease.  Other 
forms  of  filter  devised  for  bacterial  filtration  are 
the  Berkefeld  in  infusorial  earth,  the  Mallie, 
and  the  Doulton.  No  considerable  practical 
experience  is  available  in  regard  to  the  last 
two.  The  Berkefeld  was  the  filter  supplied  to 
the  British  troops  in  the  South  African  war, 
and  experience  gained  in  that  campaign,  con- 
firmed by  a  subsequent  investigation  in  the 
laboratories  of  Netley  Hospital,  showed  that, 
contrary  to  what  had  sometimes  been  hoped, 
it  could  not  give  the  required  protection 
without  precautions  and  tests  that  are  im- 
possible in  domestic  use  and  even  in  general 
institutional  practice.  Wherever  possible  a 
filter  should  be  of  the  "  pressure  "  type  and 


pressure  into  cakes  is  among  the  best.  For 
this  purpose  filter-presses  are  used,  by  which 
means  the  greater  part  of  the  superabundant 
moisture  is  removed.  A  good  type  of  filter-press 
consists  of  a  number  of  strong  corrugated 
iron  plates  placed  vertically,  each  pierced 
with  a  hole  in  the  centre,  and  having  planed 
margins  raised  somewhat  above  the  levels  of 
the  corrugations.  These  plates  are  covered 
on  both  sides  with  filter- cloth,  which  is  fixed 
around  the  centre  holes.  When  the  plates 
are  tightened  one  against  the  other  a  hollow 
space  is  found  between  each  two  plates  owing 
to  the  raised  margins.  The  end  plate  is  not 
pierced,  and  the  packing  of  the  filter-cloth 
makes  the  spaces  quite  water-tight  even  under 
pressure.  The  liquid  to  be  filtered  is  forced 
through  the  hole  in  the  first  plate,  filling  the 
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hollow  spaces  one  after  the  other,  and  driving 
the  air  out  by  way  of  an  air-valve  which  is 
closed  as  soon  as  the  liquid  is  seen  to  rise. 
As  the  pressure  is  continued,  the  liquid  is 
forced  through  the  filter-cloth,  leaving  all 
solid  matter  in  the  hollow  spaces  between  the 
plates.  After  having  passed  through  the 
cloth  the  clear  liquid  runs  down  the  corruga- 
tions, and  finds  exit  through  a  channel  to 
a  trough  outside  the  plates.  When  the 
accumulated  solids  have  filled  all  the  hollow 
spaces  (about  two-thirds  of  the  space  of  the 
whole  press),  the  shutting  arrangement  is 
loosened,  the  plates  separated,  and  the  cakes 
of  solids  allowed  to  drop  out.  These  sludge 
presses  can  be  made  with  any  desired  number 
of  plates  and  the  flanges  keeping  the  plates 
apart  can  be  made  of  such  depth  as  to 
provide  pressed  cakes  from  1  in.  in  thick- 
ness upwards.  The  amount  of  moisture 
retained  and  the  character  of  the  effluent 
depend  partly  on  the  nature  of  the  filter-cloth 
and  partly  on  the  pressure  used,  supplemented 
by  any  drying  process  adopted.  The  drying 
can  be  carried  on  while  the  cakes  are  in  the 
press,  before  it  is  opened,  by  passing  either 
hot  air  or  steam  through  the  cakes  by  an 
arrangement  of  channels,  which  ensures 
every  part  of  the  cake  being  thoroughly 
treated.  The  cakes  thus  obtained  are  quickly 
made  and  can  be  easily  handled.  The  process 
is  as  nearly  as  possible  automatic,  and  is 
cheap.  Filter-presses  of  this  description  are 
in  use  at  the  Oldham  Sewage  Works,  where 
Dr.  J.  Grossmann's  system  of  extraction  of 
fatty  acids  from  the  sludge,  and  the  utilisation 
of  the  solid  residue  as  a  fertiliser  in  the  form 
of  a  dry  sterilised  odourless  powder,  containing 
a  high  percentage  of  nitrogen,  is  being  carried 
out. 

Filtration  (of  water,  through  sand.)— 

Filter  Beds — Sand  Washing — Refilling  Beds 
after  Skimming — Length  of  Service. — Abso- 
lutely pure  water,  as  understood  by  the 
chemical  formula  H20,  does  not  occur  in 
nature,  and,  without  aeration,  is  an  un- 
palatable liquid,  not  beneficial  to  the  human 


system.  The  terms  "pure"  and  "impure;" 
as  ordinarily  employed,  are  therefore  of 
relative  significance,  and  simply  indicate  that 
a  water  is  either  fit  or  unfit  for  human 
consumption. 

Some  form  of  purification  is  necessary  with 
the  great  majority  of  waters  available  for 
public  use,  as  all  are  liable  to  contain  impuri- 
ties both  in  suspension  and  in  solution, 
consisting  of  organic  as  well  as  inorganic 
matters.  The  means  adopted  for  purifying  the 
water  supply  should  be  of  such  a  character  as 
to  render  the  water  perfectly  fit  for  drinking 
without  previous  domestic  filtration  or  boiling. 
Upland  surface  water  often  contains  animal  and 
vegetable  impurities,  and  these  sometimes 
cause  great  trouble  by  growths  and  obstructions 
in  mains  or  pipe-lines,  as,  for  example,  arose 
in  the  conveyance  of  the  Vyrnwy  water  from 
North  Wales  into  Liverpool.  Gathering  grounds 
may  also  be  polluted  with  peat,  iron,  or  even 
with  animal  excrement.  But  it  is  with  river 
and  low-lying  lake  supplies  that  the  greatest 
measure  of  risk  lies,  such,  for  instance,  as 
obtains  in  the  case  of  the  rivers  Thames  and 
Lea,  from  which  a  very  large  part  of  the 
London  supply  is  derived.  In  all  such  cases 
an  efficient  system  of  purification,  as  carried 
out  by  the  Metropolitan  Water  Board,  is  an 
absolute  necessity.  Springs  afford  a  safer 
supply,  but  their  gathering  grounds  require 
constant  supervision,  as  surface  waters  may 
at  times  gain  direct  access  to  the  water  by 
fissures.  Underground  or  deep-well  waters  are 
frequently  of  a  high  degree  of  organic  purity, 
but  are  oftentimes  highly  charged  with 
mineral  impurities  in  suspension  or  solution, 
such  as  iron,  salt,  lime,  &c.,  which  require 
removal  or  reduction  by  appropriate  means 
before  the  water  can  be  utilised  for  public 
supply. 

Attention  must  be  directed  to  the  biological 
purity  of  the  water  as  well  as  to  its  chemical 
characteristics,  and,  since  pathogenic  impurity 
may  escape  both  bacteriological  and  chemical 
analysis,  efficient  filtration  is  the  only  remain- 
ing barrier  tending  to  safeguard  the  con- 
sumer. But  even  the  most  careful  filtration 


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cannot  always  be  regarded  as  an  absolute 
safeguard,  hence  it  is  usually  wiser  to  abandon 
a  polluted  source  of  supply  whenever  an 
initially  pure  water  is  available  at  reasonable 
cost. 

FILTRATION. — The  greatest  dangers  in  a 
public  supply  is  that  the  water  should  become 
a  vehicle  for  the  dissemination  of  diseases 
such  as  typhoid  and  cholera,  and  the  con- 
nection between  sudden  outbreaks  of  this 
description  and  the  water  supply  may  be  best 
studied  from  the  official  reports  of  inquiries 
into  the  epidemics  occurring  at  Worthing 
(1893),  Maidstone  (1897),  and  Lincoln  (1905)  ; 
also  at  Hamburg  and  Altona  in  1892.  In  the 
latter  case  the  practical  advantage  of  sand 
nitration  was  proved  to  be 
very  marked,  for,  whilst 
cholera  was  rampant  in  dis- 
tricts supplied  with  Hamburg 
unfiltered  river  water,  the 
population  drinking  the 
Altona  water,  subjected  to 
careful  sand  filtration,  was 
comparatively  free,  Enor- 
mous reductions  in  the  per- 
centage of  bacteria  are 
brought  about  by  sedimenta- 
tion followed  by  sand  filtration. 
Sedimentation  affords  one  of 
the  most  important  natural 
means  of  purification,  and  is  carried  out 
upon  a  large  scale  in  connection  with  the 
supply  of  river  water  to  London,  notably 
at  the  large  settling  and  storage  reservoirs 
of  the  East  London  Waterworks  adjoin- 
ing the  Lea  at  Walthamstow  and  at  the 
new  reservoirs  constructed  for  the  purpose  of 
taking  in  Thames  water  when  the  river  is 
high,  as  recently  completed  at  Staines. 
Simple  sedimentation,  if  the  water  be  allowed 
to  stand  long  enough,  removes  nearly  all  the 
suspended  impurities,  and  carries  down  a  large 
proportion  of  bacterial  life  contained  in 
the  water,  some  50%  of  the  latter  being 
removed  by  12  days'  storage.  Purification 
by  this  process  is,  however,  slow,  and  the 
necessary  tanks  and  reservoirs  occupy  a  large 


amount  of  space  and  are  costly,  but,  where 
efficient  sedimentation  is  carried  out  and  the 
water  subsequently  passed  through  sand  filters 
in  the  best  condition,  the  number  of  microbes 
in  the  filtrate  is  found  to  be  reduced  by  as 
much  as  from  97  to  99%.  Some  of  the 
principal  factors  affecting  the  reduction  of 
bacteria  in  a  water  supply  are  :  (a)  the  length 
of  time  for  sedimentation  given  to  the  raw 
unfiltered  water ;  (b),  the  fineness  of  sand  and 
thickness  of  bed  through  which  it  is  filtered  ; 

(c)  the  rate  of  filtration  through  the  sand  bed  ; 

(d)  the  cleansing  of  the  bed,  the  renewal  of 
sand,  and  the  general  care  and  watchfulness 
of  the  attendants  in  carrying  on  the  process. 

FILTER   BEDS. — The  most  general  method 


.Brick  or  Stone 


/Brick  Under -drains 


:E 


on,  Concrete 


FIG.  1. — Section  of  Sand-Filter  Bed,  showing  arrangement  of  Brick 
Under-drains  and  Graduated  Layers  of  Filtering  Materials. 


of  purification  in  England,  where  large 
quantities  of  water  have  to  be  dealt  with,  is 
that  of  slow  filtration  through  sand.  The 
various  filtration  works  for  the  supply  of 
London  with  water  from  the  Thames  and 
Lea  are  among  the  largest  and  most  efficient 
works  of  the  kind  in  the  world. 

A  "  filter  bed  "  is  formed  by  constructing  a 
large  shallow  tank  or  reservoir,  about  8  ft. 
deep,  usually  by  excavating  partly  in  the 
ground  and  part  embanking,  and  building  the 
walls  of  brickwork  or  concrete  made  water 
tight  with  a  rendering  of  cement  mortar  or  a 
lining  of  bituminous  sheeting  overlaid  with 
4J  in.  brickwork,  or  with  concrete.  The  floor 
of  the  filter  is  given  a  longitudinal  slope 
towards  the  outlet,  and  a  cross  slope  to  the 


167 


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ENCYCLOPEDIA  OF 


FIL 


centre,  so  that'the  water  draining  through  the 
sand  may  run  to  a  common  outlet.  In 
filling  in  the  materials  into  the  filter  bed,  the 
object  to  be  kept  in  view  is  to  secure  an  open 
porous  under-layer,  and  to  this  end  the  first 
material  laid  in  is  of  the  nature  of  large 
stones  or  sea-beach  having  a  large  longi- 
tudinal open- jointed  collecting  drain  running 
through  the  centre  of  the  floor  of  the  bed  with 
small  laterals  or  branch  collecting  pipes  cross- 
ing the  bed  at  intervals  of  from  3  ft.  to  6  ft. 
The  means  of  collection  from  the  bottom  of 
the  bed  should  be  as  uniform  as  possible,  so  as 
to  secure  an  equal  rate  of  filtration  through- 
out. One  method  (Fig.  1)  is  to  form  the 
collecting  channels  with  a  3-in.  layer  of  bricks 
laid  on  an  asphalte  bottom,  and  overlaid 


9  Concrete 


To  Clear 
Water  Tank 


FlG.  2. — Section  of  Outlet  Chamber  to  Filter,  showing 
Begulation  of  Water  Head. 

with  another  course  of  bricks  placed  close 
together  to  form  a  roof  over  the  channels,  to 
carry  the  gravel  and  sand  which  is  then  laid 
in.  The  bricks  so  used  should  be  of  a  good, 
hard,  durable  quality,  not  liable  to  pulverise 
and  break  down,  otherwise  settlements  will  be 
caused  in  the  sand,  the  underdrains  become 
blocked,  and  unequal  filtration  or  leakage  will 
take  place  through  the  sand.  The  filters 
should  contain  a  layer  not  less  than  about  2  ft. 
thick  of  good,  sharp,  clean  sand,  consisting  as 
near  as  possible  of  pure  silica. 

It  is  necessary  that  means  should  be  pro- 
vided for  the  regulation  of  the  rate  of  filtration 
and  the  measurement  of  the  supply  to  each 
filter,  so  that  the  proper  amount  of  "  head  " 
of  water  may  be  maintained  on  the  sand. 
The  depth  of  water  on  the  bed  is  generally 


put  at  about  2  ft.,  and  the  rate  of  filtration 
should  not  exceed  from  4  in.  to  6  in.  vertical 
drop  per  hour — equivalent  to  from  18'75  gallons 
to  28*125  gallons  per  square  yard  of  surface 
per  hour.    A  rate  of  about  2  gallons  per  square 
foot  per  hour  is  generally  allowed  in  this  country, 
but  a  good  deal  will  depend  upon  the  condition 
of  the  water.     When  a  filter  has  been  drawn 
down  it  should  be  partly  refilled  from  below 
with  filtered  water  until  the  sand  is  covered, 
and   for  this  purpose  advantage  may   often- 
times be  taken  of  the  "  head  "  available  from 
an  adjoining  filter.     The  unfiltered  water  may 
then   be   delivered   into   the   filter,    and   the 
surface  of   the   sand  will  not   be   disturbed. 
With  the  same  object  in  view,  means  should 
also  be  provided  at  the  inlet  to  break  the  flow 
of  the  incoming  water  by  providing  a 
water  cushion  for  the  water  to  fall  upon 
and  pass  thence  quietly  on  to  the  filter. 
The  surface  of  a  sand  filter  requires 
cleaning  at  intervals  varying  from  about 
10  days  to  4  or  5  weeks,  according  to  the 
quality  of  the  water.     This  is  done  by 
skimming  off  about  J  in.  to    |   in.  of 
the  surface  of  the  sand  with  wide  flat 
shovels,  placing  the  same  in  heaps  on 
the  filter  for  removal  to  a  sand-washing 
floor.      The    sand   so    removed   is    not 
usually  immediately  replaced,  but  re- 
mains until   a   number   of    such   skimmings 
have    reduced    the    total    thickness    on    the 
beds  to  from  12  in.  to   18  in.      The   thick- 
ness is  then  made  up  to   the  original  level 
with  the  washed  sand,  which  is  well  mixed 
with  that  already  on  the  filter  bed.     Some- 
times the  top  layer  of  sand  remaining  on  the 
bed  after  the  last  skimming  is  removed  before 
putting  on  the  clean  sand,  and  afterwards  put 
on  the  top  of  the  latter  layer.     The  first  water 
from  a  filter  after  cleaning  will  not,  as  a  rule, 
be  satisfactory  for  use,  unless  the  filter  has 
been  refilled    from  below,  and    is    therefore 
frequently  run  to  waste.     This  arises  mainly 
from  the  fact  that   the  bulk  of  the  work  of 
filtration  is  done  in  the  thin  film  of  sand  on 
the  surface  of  the  filter,  which,  after  a  very 
few   days'   use,  becomes  coated  with   a  fine 


168 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


FIL 


deposit  of  mud,  and  a  gelatinous  vegetable 
growth  sets  in,  thus  forming  a  coating  which 
proves  to  be  by  far  the  most  efficient  part  of 
the  filter.  Once  formed,  the  surface  film 
should  not  be  broken  until  the  filter  requires 
cleaning. 

To  avoid  disturbance  of  the  filtering  layers 
of  sand,  it  is  necessary  to  provide  for  the  free 
passage  of  air  to  and  from  the  bottom  of  the 
filter  by  means  of  air  pipes  in  the  side  walls  of 
the  filter.     The  roofing  over  of  filters  is  not 
often  done  in  this  country,  although  there  are 
advantages  to  be  derived   therefrom   in   the 
prevention  of  frost,  and  the  exclusion  of  direct 
sunlight,  which  gives  rise  to  the  evolution  of 
gas  from  the  top  layer  of  sand,  and   causes 
patches  of  the  surface  film  to  rise  and  float  on 
the  water,  thus  leaving  bare  places   on   the 
filter  through    which  the  water    filters  more 
rapidly    than    on    the     adjoining     surfaces. 
The  area  of  filters  required  for  any  given  popu- 
lation  may   readily   be   calculated   from  the 
permissible  rate  of  filtration  already  named, 
allowing  a  supply  at  the  rate  of  from  25  to 
30  gallons  per  head,  and  adding  to  the  area  so 
arrived  at  an  additional  area  of  about  one- 
fourth  of  that  quantity.     This  additional  unit 
of    surface    is    required    so    that    any    cor- 
responding section  of  the  total  area  may  be 
thrown   out   of   use   for    cleansing    purposes 
without  interrupting  the  continuance   of  the 
supply.     For   a  supply  of  1,000,000  gallons 
per  day   an   area  of   at   least  2,800  sq.  yds. 
of  beds  would  be  required,  filtering  at  the  rate 
of    450    gallons    per    square    yard     per    24 
hours,  on  the   assumption  that  this   rate  of 
filtration  could  be  regularly  maintained.     As 
the  filters  become  "  ripe,"  however,  the  rate 
of   filtration  decreases,    and   the  quality     of 
the  effluent  increases.     Sand  filtration  does 
not,  of  course,  entirely  prevent  the  passage  of 
bacteria  through  the  sand,  and  attempts  have 
been  made  to  produce  a  perfect  artificial  filter, 
so  that  the   passage  of    bacteria   and    their 
spores  may  be  entirely  prevented  by  passing 
the  water  under  pressure  through  materials 
having  capillary  passages  sufficiently  fine  to 
attain   this  object.     Filters  of  this  type  are 


the  Pasteur-Chamberland  filter,  using  biscuit 
porcelain  as  a  filtering  medium,  and  the 
Berkefeld  filter,  in  which  baked  infusorial 
earth  is  employed.  If  properly  attended  to 
and  frequently  sterilised  these  both  give  satis- 
factory results  for  small  domestic  filtration 
purposes.  A  public  water  supply,  however, 
should  be  of  such  a  quality  as  will  render 
domestic  filtration  quite  unnecessary,  as  it 
rarely  happens  that  domestic  filtration  is 
carried  out  with  sufficient  care  and  attention 
to  yield  much  advantage  to  the  householder, 
and  in  many  instances  the  so-called  filtration 
becomes  positively  harmful. 

Efforts  have  been  made  by  means  of  the 
surface  film  upon  sand  to  increase  the  power 
of  sand  and  other  granular  materials  to  arrest 
bacteria  when  passing  through  the  pores  of 
such  substances  at  a  greater  speed  than  is 
ordinarily  permissible  for  successful  filtration. 
This  has  been  done  by  adding  coagulants, 
such  as  alum,  to  the  water  to  be  filtered. 
The  effect  is  to  quickly  produce  a  gelatinous 
substance  between  the  particles  of  the  filtering 
material. 

The  sand  used  for  filters  should  be  as 
nearly  as  possible  pure  silica,  and  be  quite 
clean  and  sharp.  The  grade  of  the  sand- 
grains  may  be  between  '005  in.  diameter 
and  '01  in.,  or  say  '008  in.  on  the  average. 
Fine  grade  sands  give  better  effluents  than 
coarse,  but  the  filters  naturally  choke  more 
readily  and  call  for  more  frequent  cleansing. 
If,  on  the  other  hand,  the  sand  should  be  too 
coarse,  the  impurities  penetrate  more  deeply 
into  the  bed,  and  so  entail  the  removal  of  a 
thicker  coating  at  each  cleansing.  It  is  often 
a  difficult  matter  to  procure  a  suitable  sand 
in  the  locality  of  filter  beds,  in  which  circum- 
stances it  becomes  necessary  to  import 
material  from  a  distance.  The  present  writer 
has  obtained  large  supplies  of  suitable  sand 
from  Hayle,  on  the  coast  of  Cornwall.  This 
may  be  placed  in  the  beds  without  washing, 
provided  the  effluent  for  the  first  day  or  two 
is  run  to  waste.  The  sand  layer  upon  the 
bed  may  be  from  2  ft.  to  3  ft.  in  thickness,  to 
allow  a  number  of  skimmings  before  renewal 


169 


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ENCYCLOPAEDIA   OF 


FIL 


with  new  sand,  or  with  the  old  sand  removed, 
the  same  having  first  been  washed. 

SAND  WASHING. — Where  plenty  of  good  and 
suitable  sand  is  readily  obtainable,  it  may  not 
prove  economical  to  wash  the  sand  skimmed 
off,  but  it  is  not  often  that  the  purchase  of 
new  sand  is  found  to  be  the  cheaper  course. 
Several  different  types  of  sand  washing  plant 
are  in  use,  such,  for  example,  as  that  of 
Hunter  &  Goodman,  as  supplied  to  several  of 
the  London  waterworks,  and  Walker's,  used 
at  Eeading.  The  main  object  is  to  secure 
thorough  cleansing  of  the  sand  skimmed  from 
the  bed  with  the  expenditure  of  a  minimum  of 
labour  and  water  in  carrying  out  the  process. 
In  many  cases  it  is  necessary  to  cleanse  the 
dirty  washwater  from  the  sand  washing  pro- 
cess, and  the  writer  has  for  many  years  used 
settling-tanks,  followed  by  shallow  filters, 
containing  about  18  in.  of  boiler  pan  -  ash, 
which  proves  very  effective  in  rendering  the 
water  fit  for  disposal  into  a  water  course. 
Sand  washing  may  cost  from  Is.  to  2s.  6d. 
per  cubic  yard,  according  to  circumstances. 

The  "filtering  head,"  or  the  difference  of 
top  water  level  within  the  bed  and  that  in  the 
"  outlet  chamber,"  determines  the  rate  of 
filtration,  and  some  suitable  means  should  be 
provided  for  regulating  the  work  being  done. 
Special  appliances  for  this  purpose  are  supplied 
by  makers  of  waterworks  apparatus,  but  all 
such  arrangements  should  be  as  simple  in 
design  as  possible,  and  involve  a  minimum  of 
attention.  The  arrangement  illustrated  in 
Fig.  2  has  been  found  to  be  simple  in 
working,  and  to  meet  all  requirements.  The 
adjustment  of  the  sluice  valve  A.  regulates  the 
quantity  of  water  passing  over  the  gauge  at  B., 
and  the  amount  or  depth  of  water  going  over 
the  gauge  is  recorded  at  the  ground  surface 
by  means  of  a  float  C.  The  valve  D.  admits 
of  the  draining  down  of  the  entire  filter  bed 
if  required. 

KEFILLING  BEDS  AFTER  SKIMMING. — It  is  a. 
good  plan,  after  cleansing  a  filter  bed,  to  refil 
the  same  with  filtered  water  to  the  height  of 
about  1  ft.,  if  possible,  from  the  bottom 
upwards,  so  as  to  avoid  entrapping  air  in  the 


interstices  of  the  sand,  and  also  to  avoid 
disturbance  of  the  surface  of  the  bed  by  the 
inflow  of  water  from  the  top.  Refilling  from 
below  is  readily  done  where  the  beds  are 
arranged  at  different  levels,  as,  by  a  proper 
adjustment  of  the  inlet  and  outlet  valves,  water 
from  the  high  level  beds  may  be  made  to  head 
back  into  those  at  a  lower  level. 

LENGTH  OF  SERVICE  OF  FILTERS. — The 
quality  of  the  water  dealt  with  is  the  principal 
factor  in  determining  the  length  of  time  a 
sand  filter  can  be  run  without  skimming.  In 
dealing  with  river  waters  and  others  con- 
taining a  good  deal  of  suspended  matter,  and 
much  microscopic  animal  and  vegetable  life, 
the  period  of  service  of  the  filter  will  be  greatly 
increased  by  preliminary  storage  and  sedi- 
mentation. The  London  filters  run  for 
80  to  40  days,  according  to  the  condition 
of  the  water  and  the  amount  of  previous 
sedimentation  which  has  taken  place.  At 
Berlin  and  Hamburg  the  usual  period  of  run 
before  scraping  is  about  40  days.  Filtering 
operations  are  oftentimes  much  interfered 
with  by  animal  and  vegetable  growths  upon 
the  beds,  which,  in  certain  seasons  of  the 
year,  are  sometimes  so  prolific  as  to  choke  the 
surface  in  a  few  days.  When  the  filter  is 
drained  down  for  cleansing,  these  surface 
accumulations  can  often  be  rolled  up  off  the 
surface  of  the  sand  like  a  carpet,  leaving  the 
clean  surface  of  sand  underneath.  The  writer 
has  experienced  much  trouble  in  this  connec- 
tion from  an  abnormal  development  of  the 
diatom  asterionella  occurring  in  a  mixed  supply 
of  underground  water  and  spring  water,  the 
mineral  constituents  of  the  former  favouring 
the  rapid  development  of  the  growth  when 
exposed  to  warmth  and  sunlight  in  open 
reservoirs  or  filters.  Keeping  the  under- 
ground water  separate,  and  treating  it  in 
mechanical  filters,  effectually  removed  the 
trouble  from  the  open  storage  reservoir  and 
sand  filter  beds. 

Binding  materials,  such  as  alum,  lime,  or 
sulphate  of  alumina,  are  sometimes  added  to  the 
water  to  be  filtered,  with  the  object  of  increas- 
ing the  power  of  the  sand  to  arrest  bacteria, 


170 


FIN 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


FIR 


&c.,  in  passing  through  the  filter.  The  effect  of 
the  coagulant  is  to  produce  a  glutinous  sub- 
stance upon  the  filtering  media,  which  acts 
much  in  the  same  way  as  the  film  of  mud  and 
vegetable  growth  which  forms  on  the  surface 
of  the  bed  after  a  few  days'  use.  Coagulants 
are  often  added  to  raw  turbid  waters,  especially 
in  America,  to  hasten  the  deposition  of  fine 
suspended  matter  previous  to  filtration. 

COST  OF  SAND  FILTERS. — This  depends  largely 
upon  local  conditions,  the  position  and 
accessibility  of  the  site,  and  facilities  for 
obtaining  suitable  materials.  Under  average 
conditions  uncovered  sand  filters  may  be 
expected  to  cost  from  £10,000  to  £12,000  per 
acre  to  construct,  and  covered  filters  (seldom 
used  in  this  country)  about  £15,000,  exclusive 
of  sedimentation  basins  and  other  extraneous 
works. 

The  working  cost  of  sand  filters  is  also  very 
variable.  In  London  the  cost  ranges  from 
3s.  to  4s.  Qd.  per  million  gallons  filtered, 
including  labour,  sand  washing,  and  all 
expenses  of  cleansing.  In  smaller  works 
the  cost  would  be  proportionately  higher. 

W.  H.  M. 

Fine  Beds. — (See  "  SEWAGE  DISPOSAL.") 

Fire  Stations    and  Appliances. — The 

site  to  be  selected  for  a  fire  station  should,  if 
it  does  not  stand  alone,  form  the  corner  of  a 
block.  Ready  egress  and  ingress  are  essential 
features  to  be  aimed  at,  and  it  is  desirable 
that  the  ingress  should  lead  to  a  rear  court- 
yard direct,  and  not  through  the  engine-house 
proper ;  a  back  entrance  to  the  engine-house 
admitting  the  engines  direct  from  the  court- 
yard. 

Owing  to  the  rapid  development  of  the 
automobile  fire  appliances,  it  is  now  first  of 
all  necessary  to  decide,  before  planning  a 
station,  whether  the  appliances  are  to  be 
horsed  or  automobile.  Unless  there  be  some 
very  cogent  reason  to  the  contrary,  there 
should  be  no  difficulty  in  deciding  in  favour 
of  the  automobile.  In  the  latter  case  examina- 
tion pits  are  necessary  under  the  engine 


stands,  and  drip  pits  6  in.  deep  let  in  the 
flooring  to  receive  the  oil  drippings  from  the 
engine.  In  the  case  of  a  steam  motor  engine 
a  shaft  connected  with  a  chimney  to  the  roof 
over  the  funnel  of  the  fire  engine  boiler  is 
required  to  carry  off  the  smoke  from  the  oil 
fuel  when  the  engine  is  lighted  up  on  starting 
out. 

Where  the  appliances  are  to  be  horsed, 
the  stables  should  be  in  the  immediate  rear  of 
the  engine,  with  the  doors  leading  from  each 
stall  opening  outwards  to  admit  of  each  horse 
being  trained  to  run  up  to  its  allotted  position 
under  harness  suspended  above  the  pole  of 
the  engine. 

STEAMERS,  HORSED. — For  residential  districts 
the  capacity  of  a  steam  fire  engine  should  not 
be  less  than  350  gallons  per  minute,  delivered 
through  a  1  in.  nozzle.  For  manufacturing 
districts  the  pumping  capacity  of  an  engine 
should  not  be  less  than  450  gallons  per  minute, 
delivered  through  a  1^  in.  nozzle. 

The  requirements  of  a  district  should  govern 
the  number  and  capacity  of  pumping  fire 
engines.  Unless  the  water  supply  for  the 
district  is  such  as  to  dispense  with  the  necessity 
of  a  pumping  engine,  the  engines  should  be 
of  sufficient  capacity  to  deliver  the  required 
number  of  1  in.  jets,  which  size  alone  can  be 
considered  as  being  the  minimum  diameter  of 
efficient  fire  jets. 

PUMPING  ENGINES,  AUTOMOBILE. — Most 
people  will  consider  that  the  steam  engine 
for  an  emergency  service  such  as  the  fire 
service  is  the  most  reliable  under  all  condi- 
tions. The  uncertainties  of  the  petrol  engine 
as  a  power  for  an  emergency  engine,  such  as 
a  fire  engine,  are  such  as  to  preclude  absolute 
reliability  (which  in  this  case  is  an  essential 
factor)  being  obtained  where  only  one  engine 
is  available.  On  the  other  hand,  where  an 
absolutely  reliable  engine  is  always  in  reserve, 
the  petrol  pumping  engine  is  decidedly  an 
acquisition  to  the  efficiency  of  a  fire  brigade. 

There  is  an  important  factor  to  be  considered 
in  deciding  as  between  a  petrol  and  a  steam 
mechanically  propelled  pumping  fire  engine. 
The  former  stands  practically  ready  to  move 


171 


FIR 


ENCYCLOPEDIA  OF 


FIR 


out  on  the  starting  of  the  engine.  In  the 
case  of  a  steam  propelled  engine  it  is  necessary 
to  have  a  sufficient  head  of  steam  in  the  boiler 
to  enable  it  to  be  started  in  a  given  number  of 
seconds.  That  is  to  say  in  brigades  where 
the  arrangements  do  not  permit  of  an 
immediate  turn  out  on  receipt  of  a  "  call," 
it  is  only  necessary  to  keep  a  head  of  steam 
so  regulated  that  the  maximum  pressure  will 
be  reached  during  the  time  which  will  elapse 


—  GROUMO  f~Loof(    PLAN 

FIG.  1. — District  Fire  Station,  London  Road, 
Edinburgh. 

before  the  men  are  able  to  assemble  at  the 
fire  station  to  proceed  to  the  fire.  If  two 
minutes  are  required  20  Ibs.  of  steam  will 
suffice,  if  one  minute  is  required  60  Ibs.  will 
suffice,  if  the  engine  is  to  be  available  for 
immediate  turn  out  a  minimum  pressure  of 
80  Ibs.  is  required. 

There  are  one  or  two  different  methods  of 
heating  the  boiler  of  the  steam  motor-engine. 
The  simplest  is  by  inserting  a  gas  ring  burner 
in  the  fire  box.  This,  however,  is  the  most 


expensive,  for  to  maintain  a  head  of  60  Ibs.  of 
steam  will  cost  about  £1  per  week.  An 
alternative  to  the  foregoing  is  to  raise  steam 
in  a  stationary  slow  combustion  boiler  to  the 
required  head,  and  connect  the  latter  to  the 
fire  engine  boiler  by  flow  and  return  pipes, 
by  means  of  which  the  steam  is  maintained 
in  the  fire  engine. 

From  the  point  of  view  of  cost  of  main- 
tenance at  the  fire  station,  the  petrol  engine  is 
the  more  economical,  but  petrol  being  so 
much  more  costly  than  the  paraffin  oil  used 
as  fuel  for  the  steam  engine,  the  over-all 
maintenance  is  almost  equally  balanced 
between  both  types  of  engines. 

HOSE  TENDER. — The  utility  of  this  class 
of  machine  consists  of  the  quantity  of 
gear  and  number  of  men  carried  upon  it. 
Whether  horsed  or  mechanically  driven,  a 
useful  hose  tender  should  carry  from  1,200 
to  1,800  ft.  of  hose,  4  stand  pipes,  8 
branch  pipes,  nozzles,  breechings,  hand- 
pumps,  lines,  scaling  and  hook  ladders, 
jumping  sheet,  lamps,  &c. 

HORSED  ESCAPE.  —  A  machine  having 
almost  the  same  carrying  capacity  as  a 
hose  tender,  carrying  in  addition  a  fire 
escape  of  an  average  height  of  50  ft. 
which  is  secured  in  position  by  an  easily 
detachable  mechanical  device. 

CHEMICAL  ENGINE. — The  chemical  engine, 

or  chemical  cylinder,  as  constructed  in  this 

country,  is  an  addition  to  a  hose  tender  or 

horsed  escape  in  the  form  of  one  or  two 

cylinders  of  from  30  to  60  gallons  capacity 

which  are  charged  by  gas  generated  by  a 

mixture  of  bicarbonate  of  soda  and  nitric 

acid.     Another,    and    latterly   more   largely 

adopted  method  of   supplying  gas  power  to 

discharge  the  water  from  the  large  cylinders, 

is  to  carry  compressed  air  in  high  pressure 

cylinders    which    are    connected    up   to  the 

water  cylinders  and  controlled  by  valves.    The 

advantage   of    the   compressed   air   over  the 

chemically  produced  gas  pressure  is  that  as 

soon  as  the  water  cylinder  has  been  discharged 

on  the  fire,  the  latter  may  be  refilled  and  the 

compressed  air  cylinder  is  again  available  for 


172 


FIR 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


FIS 


immediate  use.  A  60-gallon  cylinder  will 
discharge  an  effective  jet  of  water  of  |  in.  to 
-j%  in.  diameter  at  high  pressure  to  a  distance 
of  40  ft.  for  eight  minutes. 

TURNTABLE  LADDER. — These  machines  are 
built  from  60  ft.  to  85  ft.  in  length,  and  consist 
of  three  or  four  telescopic  section  ladders. 
They  are  built  on  a  mechanically  revolving 
base  on  a  low  platform,  and  may  be  obtained 
with  either  hand  power  or  mechanical  extend- 


NOZZLES. — There    are     various    forms     of 
nozzles  now  in  use ;  the  most  useful  nozzles 
for   fires    requiring    one    or    two    deliveries 
being    those   controlled    by   a   shut-off  valve 
on  the  branch-pipe  known  as  the  "  London  " 
nozzle,    which  is   provided  with    one   nozzle 
outlet.     Another,  and   more   effective   nozzle 
is  the  "  Multiplex,"  which  has  the  alternative 
of   three  sizes  of  nozzle,  viz.,  \  in.,  ^  in., 
and   |  in.,  and  a  shut-off.     This  is  a  useful 
nozzle,  as  it  provides  one  of  four  alter- 
natives which  may  be  obtained  without 
shutting  off  the  water.     Shut-off  nozzles 
should    only    be    used    on    gravitation 
pressures.     Steamers  and  other  pump- 
ing engines  should  use  the  "  Multiplex  " 
"  Steamer "    nozzle    which     has    three 
sizes :   f  in.,  f  in.,  and  1  in.,  without 
a  shut-off.  A.  P. 


(,o  FEET 


FlG.  2. — District  Motor  Fire  Station,  Stockbridge, 
Edinburgh. 

ing  gear.  The  latter  is  an  ingenious  engine, 
which  derives  its  power  from  compressed  air 
or  gas,  in  cylinders  carried  on  the  machine. 
Four  such  cylinders  are  usually  carried,  and 
will  raise  the  ladder  to  its  extreme  height, 
an  average  of  several  times.  These  ladders 
are  indispensable  to  fire  brigades  in  districts 
where  the  buildings  are  above  the  average 
height,  as  they  are  readily  available  either  for 
saving  life  or  for  use  as  a  water  tower. 


Fish  Life  in  Streams. — The  well- 
known  fact  that  fish  are  greatly  affected 
by  the  condition  of  streams  has  led  to  the 
proposal  of  a  "  fish  test "   for  effluents, 
namely,  that  their  quality  should  be  such 
that  fish  live  healthily  in  them.     Such 
a    definition    involves    necessarily    the 
absence  of  poisons  and  the  presence  of 
dissolved  oxygen.    But  while  an  effluent 
that  kills  fish  is  obviously  unhealthy,  it 
does  not  follow  that  one  where  fish  will 
live    is    therefore  a  good    one.      Fresh 
water   species   are    gross    feeders,    and 
are  often    seen    in    large    numbers     at 
the     mouths    of    sewers,    where     faecal 
matter  is  visibly  floating,  being  attracted 
by  the  insects,  Crustacea,  and  fragments 
of    food.      They    are,    in     fact,    more 
affected  by  muddy  water  and  by  chemicals 
from  factories  than  by  excreta,  which  some 
actually  feed  on.     Perch  and  trout  can  live  in 
water  holding  3  or  4  c.c.  of  oxygen  in  solution 
out  of  the   average  of  7   c.c.   per  litre,   but 
are  soon  asphyxiated  when   only  1/7  c.c.   is 
present.       They   are    not    injured    by    car- 
bonic   acid   till   10   to  15  %  by  volume    is 
reached.     Fish  often  die  at  once  when  placed 
in   an    effluent   from   chemical   precipitation 


173 


FIS 


ENCYCLOPEDIA   OF 


FLO 


with  lirne  and  ferrous  sulphate,  on  account  of 
deficiency  of  dissolved  oxygen. 

Fish  as  a  rule  prefer  clear  streams,  and 
only  enter  muddy  water  for  food  and  for 
breeding  purposes.  Heavy  sediments  act 
injuriously  by  covering  the  bed  and  closing  up 
resting  places,  and  in  spawning  grounds  by 
interfering  with  the  ova  and  cutting  off  the 
light  that  is  necessary  for  normal  develop- 
ment. But  it  is  pointed  out  that  as  salmon 
traverse  the  long  muddy  reaches  of  the  Usk, 
the  Humber,  and  the  upper  Severn,  the  mud 
and  silt  of  these  rivers  cannot  be  inimical  to 
grown  fish,  or  at  all  events  to  salmon.  A 
chemical  investigation  of  the  sediment  in 
rivers  is  of  great  importance.  In  one  case 
the  mud  for  over  400  yds.  below  a  works  dis- 
charge was  impregnated  with  naphthalene 
products,  and  when  disturbed  was  poisonous 
to  river  life,  and  the  writer  found  the  deposit 
below  a  paper  mill  to  contain  gypsum,  chalk, 
and  various  pigments,  and  that  below  a 
copper  works,  to  contain  this  metal ;  the  fish 
in  both  were  injuriously  affected.  The  effluent 
from  lead  mines  is  similar.  In  another  river 
where  the  fish  had  died,  he  observed  the 
sediment  to  be  black  from  ferrous  sulphide  : 
the  water  contained  much  ferrous  iron  in 
solution,  which  had  robbed  it  of  dissolved 
oxygen,  and  had  modified  the  aquatic  vegetation 
to  anaerobic  and  semi-aerobic  kinds  causing 
offensive  odours.  Sharp  quartz  particles  and 
coal  washings  may  cause  injury  to  the  eyes, 
gills,  or  even  the  skin  of  fish,  which  are  some- 
times "  smothered,"  through  mechanical 
clogging  of  the  gills  by  a  discharge  of  sludge 
when  a  mill-dam  is  opened,  and  in  certain 
cases  by  storm  water.  The  same  effect  has 
occurred  from  the  abundant  growth  of 
"distillery  fungus,"  leptomitus  lacteus,  where 
"  burnt  "  ale,  spent  lees,  and  general  waste 
are  sent  into  streams.  In  America,  great 
destruction  of  fisheries  has  been  occasioned 
by  the  discharge  of  sawdust.  In  these  cases 
also,  deficient  aeration  is  at  work,  since  all 
crude  effluents,  heavily  loaded  with  organic 
matter,  such  as  the  above,  and  those  from 
starch  factories,  tanneries,  &c.,  deprive  the 


liquid  of  free  oxygen,  hence  the  chemical 
figures  of  dissolved  oxygen,  and  oxygen  con- 
sumed, should  be  continually  watched  in 
relation  to  their  amounts  in  the  river  and  the 
volumes  of  the  two  waters  mixing.  As  dis- 
tinguished from  fungus  growths,  green  aquatic 
vegetation  renews  the  dissolved  oxygen,  and 
when  not  too  dense  gives  a  shelter  to  fish, 
and,  by  their  feeding  on  it,  is  hindered  from 
overgrowth.  In  certain  cases  the  pollution  of 
estuaries  and  shores  has  also  done  damage  to 
sea  fish.  At  low  temperatures,  while  the 
solubility  of  oxygen  in  water  is  greater,  the 
amount  required  to  support  fish  life  has  been 
shown  to  be  much  less  ;  therefore  it  is  in  the 
summer  that  special  regard  must  be  given  to 
the  oxygen  content  of  streams.  Other  factors, 
such  as  disturbance,  injury  to  spawning 
grounds,  and  obstructions  to  access,  require 
consideration,  and  an  increase  of  the  number 
of  birds  that  feed  on  fish  may  render  the 
latter  scarcer.  Under  conditions  of  proper 
dilution  and  aeration,  the  discharge  of  sewage 
or  of  sewage  effluents,  is  beneficial  to  fish, 
since  it  nourishes  Crustacea,  such  as  shrimps, 
and  other  small  life  which  then  form  the 
fishes  food.  But  from  polluted  rivers  it  has 
been  shown  that  the  colon  bacillus  is  taken 
up  by  fish  and  multiplies  rapidly  in  their 
intestinal  tract,  while  its  absence  was  noted 
in  fish  from  unpolluted  waters,  and  it  seems 
likely  that  typhoid  and  other  pathogenic 
organisms  may  be  carried  by  fish  migration. 

For  further  details  on  the  subject  see  the 
reports  of  the  Eoyal  Commissions  on  Salmon 
Fisheries,  1902,  and  on  Sewage  Disposal,  1908, 
Appendix  VI.  S.  R. 

Flash  Point.— (See  "OiL  ENGINES.") 

Floating  Arms. — Floating  arms  are  em- 
ployed to  draw  off  the  supernatant  liquid  from 
precipitation  and  sedimentation  tanks  without 
disturbing  the  sludge  which  has  been  deposited 
in  them.  They  are  also  used  to  empty  water- 
filters.  The  arm  consists  of  a  trunk,  generally 
of  iron,  and  rectangular  in  section,  pivoted 
at  its  lower  end  on  the  outgoing  pipe,  and 


174 


FLO 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


FLO 


having  at  its  upper  end,  which  is  open,  a 
float,  so  placed  as  to  hold  the  mouth  of  the 
trunk  just  below  the  water  level.  When  the 
tank  is  full,  the  arm  is  steeply  inclined,  but, 
as  the  liquid  is  drawn  off,  it  gradually  falls, 
until  it  rests  in  a  nearly  horizontal  position 
on  the  floor,  the  level  of  the  mouth  meanwhile 
keeping  pace  with  that  of  the  surface  of  the 
liquid.  A.  J.  M. 

Flow  in  Pipes   and   Conduits. — Laws 
of    Fluid    Friction  —  Hydraulic    Gradients  - 
Hydraulic    Mean    Depth  —  Velocity    in    Pipes 

-  Formulae  —  Futility    of    Close    Calculations 

-  Discharge  —  Head   for   Velocity  —  Velocity 
in    Sewers.  —  The    velocity     of     flow    in    a 
pipe  or  conduit   depends  upon   the   relation 
between  two  opposing  forces — the  factional 
resistances    within   the   pipe,  and   the 
power  available  for  overcoming  them. 
Although  for   practical  purposes   it  is 
convenient   to   regard   the   velocity   as 
being  uniform  all  over  the  cross-section 

of  the  flow,  this  is  very  far  from  being 
the  case.  The  layer  of  fluid  in  contact 
with  the  sides  is  retarded  by  friction,  and 
moves  very  slowly:  the  centre  of  the  stream 
is  subject  to  no  such  impedance,  and  the 
velocity  here  is  much  above  the  average. 
This  consideration  seems  to  point  to  the 
existence  of  a  number  of  concentric  cylinders 
of  fluid,  each  sliding  within  the  other  at  a 
rate  which  gradually  increases  as  they 
approach  the  centre.  The  actual  state  of 
affairs  is  much  more  complex.  In  all  but  the 
smallest  pipes  the  contents  move  in  a  series 
of  eddies,  more  or  less  irregular,  but  having  a 
general  tendency  to  roll  like  wheels  along  the 
side.  A  large  part  of  the  power  to  which  the 
motion  is  due  is  thus  expended  in  overcoming 
the  viscosity  of  the  fluid. 

LAWS  OF  FLUID  FRICTION. — Fluid  friction  is 
subject  to  the  following  laws  :  (1)  The 
resistance  due  to  friction  is  not  affected  by 
differences  in  pressure  ;  that  is  to  say,  the 
friction  in  a  water-main  at  a  given  velocity  is 
the  same  whether  the  water  is  merely  running 
freely  without  pressure,  or  is  subject  to  a 


pressure  of  several  hundred  pounds  to  the 
square  inch.  The  same  formulae  and  tables 
therefore  hold  good  irrespective  of  the  pressure 
in  the  pipes.  (2)  The  frictional  resistance  is 
proportional  to  the  area  of  the  wetted  surface. 
(3)  At  very  low  velocities  the  frictional 
resistance  is  directly  proportional  to  the  speed ; 
but  when  the  velocity  is  over  6  in.  per  second 
the  resistance  increases  approximately  as  the 
square  of  the  speed.  (4)  The  frictional 
resistance  is  governed  by  the  nature  of  the 
surface  of  the  conduit.  It  was  at  one  time 
believed  that  the  former  was  independent  of 
the  latter,  the  fluid  being  supposed  to  slide 
along  a  thin  film  held  in  contact  with  the 
surface  of  the  conduit.  Subsequent  experi- 
ments have  shown  that  this  is  not  the  case, 
and  that  the  nature  of  the  material  of  a  pipe 


FIG.  1. 

or  conduit  exercises  a  marked  effect  on  the 
rate  of  flow  in  it.  The  force  which  causes  the 
flow  in  a  pipe  is  usually  that  of  gravity,  and 
is  measured  by  the  fall,  or  the  loss  of  pressure 
or  "head"  in  a  given  length  of  pipe.  In 
some  cases  it  is  convenient  to  express  the 
power  expended  in  overcoming  friction  as  so 
many  pounds  per  square  inch ;  but  in  dealing 
with  water-mains  or  sewers  it  is  more  usual 
(in  this  country  at  any  rate)  to  speak  of  the 
virtual  inclination,  or  "  gradient,"  of  the  flow. 
Thus  a  pipe  1,000  ft.  long,  which  conveys  water 
from  one  reservoir  to  another  having  its  level 
10  ft.  lower,  is  said  to  work  under  a  head  of 
10  ft.,  or  at  a  gradient  of  1  in  100  (—  10  in 
1,000).  In  America  this  would  be  called  a 
grade  of  1  %,  or  52'8  ft.  per  mile. 

HYDRAULIC  GRADIENT. — The  gradient  on 
which  the  flow  in  a  pipe  depends  is  not 
necessarily  that  at  which  the  pipe  itself  is  laid, 
but  is  the  "  hydraulic  gradient,"  that  is  to  say 
the  slope  from  the  water  level  at  the  source  to 
that  at  the  point  of  discharge ;  or,  if  the  water 


175 


FLO 


ENCYCLOPEDIA   OF 


FLO 


is  delivered  under  pressure,  to  the  level  to 
which  it  would  rise  in  a  vertical  pipe 
erected  at  that  point  (see  Fig.  1).  Inter- 
mediate changes  in  the  inclination  of  the 
pipe  do  not  affect  the  flow,  provided  that  no 
part  of  it  rises  to  a  height  of  more  than  34  ft. 
above  the  hydraulic  gradient.  It  is  not 
desirable,  however,  that  any  part  of  the  pipe 
should  rise  above  the  gradient  line,  as  the 
consequent  reduction  in  pressure  is  apt 
to  lead  to  the  disengagement  of  dissolved  air, 
which  would  accumulate  at  the  upward  bends 
and  obstruct  the  flow.  Similar  accumulations 
are  apt  to  take  place  at  all  high  points,  even  be- 
low the  line  of  the  hydraulic  gradient.  Suitable 
automatic  valves  should,  therefore,  be  placed 
at  all  summits,  to  prevent  the  accumulation  of 
air.  In  the  case  of  a  "rising  main,"  the 
hydraulic  gradient  will  start  from  the  point  to 


]HMD 


HI- CIRCUMFERENCE H 

FIG.  2. 

which  the  water  would  rise  in  a  vertical  pipe 
carried  up  from  the  pump. 

The  power  which  maintains  the  flow  in  a 
conduit  is  equal  to  the  weight  of  the  fluid 
multiplied  by  the  fall,  or  loss  of  head.  The 
resistance  to  the  flow  depends  on  its  velocity 
and  on  the  area  of  the  surface  with  which  the 
fluid  is  in  contact.  The  circumference  of  a 
circle  is  shorter  than  the  sides  of  a  square  of 
equal  area.  The  frictional  resistance  in  a 
round  conduit  will  therefore  be  less  than  that 
in  a  square  one,  having  the  same  cross- 
sectional  area,  and  the  former  will  have  a 
higher  velocity  than  the  latter  with  the  same 
loss  of  head.  For  a  like  reason  the  velocity 
in  a  large  pipe  will  be  greater  than  that  in  a 
small  one. 

HYDRAULIC  MEAN  DEPTH. — If  the  circum- 
ference of  a  pipe  were  straightened  out,  as 
in  Fig.  2,  to  form  one  side  of  a  rectangle 
having  the  same  area  as  the  pipe,  the  depth 


of  this  rectangle  would  be  equal  to  one- 
quarter  the  diameter  of  the  pipe.  This  depth 
is  called  the  "hydraulic  mean  depth" 
(h.m.d.) — sometimes,  less  appropriately,  the 
"  hydraulic  radius."  The  hydraulic  mean 
depth  of  any  cross-section  maybe  obtained  by 
dividing  the  area  of  flow  by  the  "  wetted 
perimeter,"  and  the  velocity  in  any  such  cross- 
section  will  be  equal  to  that  in  the  circular 
pipe  having  the  same  h.m.d.  and  hydraulic 
gradient.  Tables  of  pipe  velocities  may  there- 
fore be  used  to  obtain  the  rate  of  flow  in 
conduits  of  any  form. 

VELOCITY  IN  PIPES  KUNNING  PARTLY  FULL. — 
The  h.m.d.  and  velocity  in  a  pipe,  such  as  a 
sewer,  running  half  full  are  equal  to  those  in 
the  same  pipe  running  full  bore ;  and  with 
depths  greater  than  half  the  diameter  the 
rate  of  flow  will  be  even  higher.  The 
maximum  velocity  (1'14  times  that  in  the  full 
pipe)  occurs  when  the  depth  of  flow  is  about 
four-fifths  of  the  diameter,  and  the  maximum 
discharge  (1*08  times  that  of  the  full  pipe) 
with  a  depth  of  fifteen-sixteenths  of  the 
diameter.  On  the  other  hand,  with  depths 
less  than  half  the  diameter  the  velocity  is 
less  than  that  of  the  full  sewer.  Fig.  3  shows 
the  proportional  velocities  and  discharges  for 
a  pipe  running  partly  full,  those  for  the  full 
pipe  being  taken  as  unity. 

FORMULA. — Within  the  limits  of  ordinary 
practice  the  rate  of  flow  was  formerly  believed 
to  be  proportional  to  the  square  root  of  the 
product  of  the  hydraulic  mean  depth  and  the 
hydraulic  gradient,  and  the  older  formulae 
were  constructed  on  this  basis.  The  first 
regular  formula  was  that  introduced  by  Chezy, 
and  was  as  follows : —  v  =  c  Vr  s,  r  being 
the  velocity  in  feet  per  second,  r  the  h.m.d. 
in  feet,  s  the  slope,  or  fall  divided  by  the 
length,  and  c  a  constant  to  be  determined 
by  experiment.  Different  values  for  this  con- 
stant have  been  obtained  by  various  investiga- 
tors. Eytelwein  fixed  it^at  about  95,  and  his 
formula  -  -  v  =  95  Vr  s  — was  widely  used 
down  to  the  latter  part  of  the  last  century. 

The  rates  of  flow  given  by  this  and  similar 
formulae  are  found  to  be  too  high  in  the 


17C 


FLO 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


FLO 


case  of  small  pipes,  and  too  low  in  that  of 
large  ones,  the  velocity  as  a  matter  of  fact 
increasing  faster  than  the  square  root  of  the 
hydraulic  mean  depth.  This  fact  is  taken 
account  of  in  the  formulae  now  in  use,  in 
some  of  which  also  the  constant  increases 
with  the  gradient  as  well  as  with  the  h.m.d. 
The  arrangement  of  some  of  these  formulae 
has  in  course  of  time  been  varied  from  that 
adopted  by  their  authors,  the  symbols  in 
particular  having  been  changed  by  different 
writers  on  the  subject.  In  the  present  article, 


Ganguillet  and  Kutter's  : 


v  = 


41-6 


1-811 


•00281 


1  +    41-6 


•00281 


rs. 


n  being  a  coefficient  for  roughness,  varying 
from  0'009  for  well-planed  timber  to  O'OSOior 
torrential  streams  encumbered  with  detritus. 
For  pipes  of  cast-iron  or  stone-ware  n  lies 
between  O'OIO  and  0'013. 

For  ordinary  use  Darcy's  formula  is  simpli- 


120 
no 


100 


90 
80 


70 


60 


50 


TT 


120 


IOO 


O  -IO  -20  -20  -4O  SO 

Proportional  Depth 

FIG.  3. 


•60 


•70  -SO 


-90  I-OO 


for  the  sake  of  clearness,  the  same  symbols 
have  been  used  throughout. 

Among   the    better   known    of    the    more 
recent  formulae  are  the  following  :— 


Weisbach's  :     v  = 


d  s 


•01489  +  - 


V  V 


in  which  g  =  acceleration  due  to  gravity  =  32 '2 
and  d  =  diameter  of  pipe  in  feet      =  4r. 


Darcy's :  v  = 


2/7  rs 


•0037285  ( 1  + 


Neville's :  v  =  140  V  rs  -  11 

M.S.E. 


177 


fied  by  the  substitution  for  the  denominator 
of  his  fraction  of  a  multiplier  c,  which  ranges 
from  65  for  \  in.  pipes  to  113'3  for  very  large 
ones,  the  formula  thus  taking  the  same  form 
as  Chezy's,  viz.,  v  =  c  Vrs.  Kutter's  formula 
is  far  too  complicated  for  ordinary  use,  and 
several  simplifications  of  it  have  been'-pro- 
posed  which  give  substantially  the  same 
results.  One  of  the  most  convenient  of 
these  is  that  devised  by  the  late  Mr.  Santo 
Crimp  and  Mr.  Bruges,  and  used  by  them  in 
the  preparation  of  their  admirable  "Tables 
and  Diagrams "  of  velocity  and  discharge. 
This  formula,  in  which  the  cube  root  of 
the  square  the  hydraulic  mean  depth  is 


FLO 


ENCYCLOPEDIA   OF 


FLO 


substituted  for  the  square  root  of  the  latter, 

is  as  follows :  v  =  124  Vr*  V  s.  The 
close  agreement  between  the  results  of  this 
formula  and  those  obtained  from  Kutter's,  and 
their  very  wide  divergence  from  those  yielded 
by  some  of  the  older  formulae,  will  be  seen 
from  Fig.  4,  which  shows  the  gradient  required 
according  to  the  various  formulae  to  give  a 
velocity  of  3  ft.  per  second  in  pipes  of 
different  diameters.  These  formulae,  and  the 
tables  which  have  been  worked  out  from  them, 


deviations  in  the  diameter  of  a  pipe  of 
moderate  size  may  easily  affect  its  carrying 
capacity  to  the  extent  of  several  cubic  feet  per 
minute,  while,  as  Messrs.  Crimp  and  Bruges 
point  out  in  the  preface  to  their  tables,  the 
variations  due  to  the  smoothness  or  roughness 
of  the  pipes  may  range  up  to  20  %.  The 
effects  of  corrosion  or  incrustation  will  often 
be  still  more  serious,  water-mains  having  been 
known  to  lose  more  than  half  their  capacity 
from  these  causes. 


36 
33 
30 
27 
24 
21 
IB 


^      IS 

±      12 


w< 


100       ZOO 

Gradient 


too 


6OO 

FIG.  4. 


800 


1000 


I2OO 


hold  good,  not  only  for  water  and  sewage,  but 
for  liquids  and  gases  of  all  kinds.  It  would, 
however,  be  inconvenient  in  practice  to  have  to 
calculate  the  pressure  of  a  gas  in  terms  of  the 
height  of  a  column  of  itself.  The  pressures  of 
steam  and  compressed  air  are  therefore 
'  expressed  in  pounds  per  square  inch,  and  low 
pressures,  such  as  those  of  lighting  gas,  in 
inches  of  water. 

FUTILITY  OF  CLOSE  CALCULATIONS. — One 
sometimes  sees  the  carrying  capacity  of  a 
pipe  worked  out  to  many  places  of  decimals. 
Such  minuteness  of  calculation  is  quite  useless, 
as  it  presupposes  a  degree  of  accuracy  which 
neither  the  formula  nor  the  pipes  employed 
are  capable  of  attaining.  The  allowed 


DISCHARGE. — The  discharge  is  arrived  at  by 
multiplying  the  cross-sectional  area  of  the 
stream  by  the  velocity  :  thus  Q  =  a  v,  where  Q 
=  cubic  feet  per  second,  a  =  cross-sectional 
area  in  square  feet,  and  v  =  velocity  in  feet  per 
second.  In  circular  pipes  running  full  Q  = 


-  d?  v,  d  being  the  diameter  in  feet. 


Where 


the  discharge  is  given  in  cubic  feet  per  minute, 
it  can  readily  be  converted  into  gallons  per 
day  by  multiplying  by  9,000.  A  convenient 
mode  of  arriving  at  the  approximate  discharge 
in  gallons  per  minute  direct  from  the  velo- 
city is  to  multiply  .the  velocity  in  yards 
per  minute  by  the  square  of  the  diameter 
in  inches,  and  divide  by  10.  The  results 


178 


FLO 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


FLO 


thus   obtained   are    about   2  %   short    of   the 
true  ones. 

The  following  tables,  which  are  worked  out 
from  Crimp  and  Bruges'  formula,  cover  most 
of  the  cases  met  with  in  ordinary  practice  : — 


0 

1O  CO  O  X 
^H  CO  CO  CO 

^  CO  CD  CO  E~ 
*  ic  CD  t-  OS 

D  CO  rt<  •*!« 

0  CO  O  ^  1 
•H  rH  CO  CO  1' 

C  CO  C-  rH 

9 

t-  ic  co  co 

rH  CO  CO  -^ 

N  CO  CO  •*  C- 

C  CO  t-  X  O 

C  Tt<  CO  O 
•*  X  CO  L— 
-H  rH  CO  CO 

^-  Tt<  CO  •* 
H  CD  rH  CO 

•o  co  -*  •* 

Hb 

OS  X  C~  t~ 

rH  CO  CO  -^ 

X  O  rH  ^  O 

O  t-  X  OS  CO 

rH 

—  1  1C  CO  rH 

n  o  >c  o 

-l  CO  CO  CO 

•O  CO  rH  t- 

O  O  CD  rH 

M 

H 

*H 

4? 

rH  T-H  CO  CO 

CO  SO  ^ti  kC 

1C  X  rH  1C  ^ 

•£>  L—  OS  O  CO 
rH  rH 

rH  O  CO  X 

x  co  x  co 

rH  CO  CO  CO 

iC  1C  CD  O 
3S  1C  r-  1  X 

ro  ^  kC  ko 

M 

o 

O 

J 

- 

•*  ic  t-  o 
co  co  -^  co 

Tf  X  CO  OS  rH 
t-  X  O  r-l  kO 

r-H  rH  rH 

^  CO  OS  rH 
O  CO  rH  X 

co  co  co  co 

CO  CO  CO  1C 

"^  r-H  X  1C 

rt<  >c  ic  co 

M 

!> 
a 

£«    «H- 

o  m 
o 

[~  O  •<*  X 
CO  TJI  O  CO 

Tt<  O  t-  O  CO 
X  O  rH  CO  t- 

rH  r—  1  rH  rH 

co  co  co  "* 

TO  OS  CD  CO 
CO  CO  CO  rt* 

X  -*  CO  1C 
O  X  CO  "* 
1C  kC  CO  t~ 

M 

O 

o> 

—  T-; 
e 

3  rH  CO  CO  X 

1-1  co  Tf  co  t- 

rH 

•-O  1C  O  1C  X 
O5  rH  CO  1C  OS 
rH  rH  rH  rH 

CO  O  t-  X 

tO  -TtH  rH  OS 

CO  rH  CO  kO 

XI  t~  CO  1C 

o  to  t-  oo 

M 

O 

A 

CD   ^* 

<a  OT 

_|j  CD  CO  T—  1  rH 
S  CO  1C  t~  OS 

0) 

CO  •*  CO  O  OS 

rH  CO  1C  X  CO 
rH  rH  rH  rH  CO 

os  rt<  ^  x 

O  OS  X  t- 

co  co  ^fi  ic 

•-D  X  CO  CO 
C-  L—  X  OS 
CD  C-  X  OS 

w 
M 

1 

'o 

r3  CO  CO  ^t1  L— 

S-t  •«*  CD  X  O 

o    --1 

rH  t~  CO  rH  OS 
CO  kC  X  rH  CD 
rH  rH  rH  CO  CO 

CO  CO  X  X 
C  CD  CD  L- 
CO  •*  1C  CO 

OS  rH  CO  CO 
L—  OS  O  rH 
rH  rH 

M 

M 

92 

H 

0  Tj*  0  t- 

1C  t-  O  CM 

rH  rH 

CO  CO  X  rH  O 
0  X  rH  'C  CO 
T-H  T-H  CO  CO  CO 

rH  O  1C  t- 

CO  kC  t-  O 

^  1C  CO  X 

•rj*  CO  CO  1C 

Tj<  x  co  x 

OS  O  CO  CO 
rH  rH  rH 

RADIEI 

a 

rH  O  rH  T)< 

co  os  co  iff 

rH  rH 

OS  CO  •*  -*  X 
X  CO  CD  O  X 

rH  CO  CO  CO  CO 

CO  1C  t-  CD 

CO  CO  rH  t- 

O  CO  X  OS 

co  -*  co  co 

T}<  rH  OS  D- 
rH  CO  rfl  CO 
r-  rH  rH  i—  1 

O 

cq 

1C  rH  OS  O 
t-»  rH  "^f  OS 
rH  rH  rH 

CO  OS  CD  k-C  X 
CO  t-  CO  L-  C- 
CO  CO  CO  CO  -* 

•^  rH  OS  1C 

rt*  <M  O  O 
CO  X  O  CO 

rH  CO  CO  OS 
rH  CO  TJH  CO 

-*  CO  X  O 

CJ 

0, 

•0  O  X  O 
OS  Tf  X  ••* 
rH  rH  CO 

1C  CO  CO  1C  >C 
OS  O  i—  1  L-  O 
CO  CO  ^  ^f*  CO 

1C  O  t-  1C 

—  i  ••*  t-  co 

X  O  CO  kO 

rH  rH  r-  1 

ic  -rfi  co  os 

X  1C  CO  rH 

C~-  O  CO  CO 

rH  CO  CO  CO 

S 

5 

co  -^  o  co 

t-  X  OS  O  CO 
rH  rH 

0  X  rH  ^ 
r-H  rH  CO  CO 

c-  o  co  co 

co  co  co  co 

velocity  in  question  can  never  be  attained  in 
the  length  of  the  sewer. 

LIMITS  OF  VELOCITY. — It  has  been  said  that 
the  velocity  in  a  water-main  should  be  between 
2  and  4^  ft.  per  second  ;  and  occasionally  3  ft. 


The  flow  in  a  pipe  is  seriously  impeded  by 
elbows,  sharp  bends,  square  junctions  or 
sudden  expansions  or  contractions. 

HEAD  FOE  VELOCITY,  &c. — The  gradient 
given  in  the  tables  for  any  velocity  is  that 
which  will  maintain  the  velocity  stated,  and 
does  not  take  account  of  the  head  required  to 
generate  that  velocity  in  the  first  place,  nor 
(in  the  case  of  a  pipe  from  a  reservoir)  of  the 
head  expended  in  overcoming  the  resistance 
of  the  entrance  to  the  pipe.  In  long  W7ater- 
mains  the  head  needed  for  these  purposes  may 
generally  be  disregarded,  but  with  a  short, 
steep  sewer  that  required  to  generate  the 
tabled  velocity  will  often  be  so  great  that  the 


t-  CO  OS  OS 

0 

*a 

•<*  CO  O  X 
rH  CO  •*  1C 

D  >C  CO  -^  CO 
0  O  CO  CD  CO 
rH  rH  i—  1  CO 

0  O  CO  CO 
3  CO  CO  -r)H 
•J  1C  C-  OS 

0  CO  CO  T-I 
»  t-  X  CO 
H  Til  t-  rH 

H  r-H  rH  CO 

O  OS  OS  O 

*q  o 

our 

•* 

TJH  TJH  X  CO 

rH  CO  CO  1C 

0  OS  CO  »C  T(f 
—  OS  CO  kC  CO 
rH  rH  CO 

D  Tj*  CD  kC 
-5  O  X  OS 
O  O  CO  X 

O  OS  CO  1C 

o  os  os  •—  * 

H  CO  CD  O 
-1  rH  rH  CO 

CO  CO  X  O 

NI  CO 

-*< 
•# 

CO  CO  CO  CO 

rH  CO  CO  O 

N  TH  OS  C-  CO 

--  OS  rH  Tj<  rH 

i—  1  r-  1  CO 

H  t-  O  X 
•O  t-  kO  T(* 

O  •<*  CO  X 

^  1C  -^  OS 

:-  CO  O  O 
O  CO  CD  OS 
•H  rH  rH  rH 

VC  SO  X  rH 

M  O 

i-H- 
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(M  CO  Tj<  O 

rH  CO  CO  >C 

X  OS  CO  OS  O 

£1  X  rH  CO  O 
rH  rH  CO 

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p—  1  1C  rH  O 
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^H  X  1C  CD 
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OS  rH  "*  CO 
rH  rH  rH 

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CO  rH  X  CO 
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CO  t-  OS  CO  CO 
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CO  rH  CO  1C  Th 

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per  second  is  mentioned  as 
ought  not  to  be  exceeded, 
velocity  is  not,  however,  one 


179 


the  limit  which 
The  question  of 
to  be  settled  by 

N2 


FLO 


ENCYCLOPEDIA   OF 


FLO 


any  hard  and  fast  rule,  as  the  best  rate  to 
adopt  is  different  in  nearly  every  case.  For 
a  rising  main,  for  instance,  there  is  a  certain 
size  at  which  the  interest  on  the  cost  of  the 


Proportional  Velocities  and  Discharges  in  Pipes  running  partly  full,  those  for  full  Pipes 
being  taken  as  Unity. 

§<N  t- 
T1  9 

TH  TH 

• 

t- 
O  •>*  t- 

00  TH  OS 

TH 

<M 

O  CO  iH 
C~  TH  Oi 

t- 

O  <N  CO 

C-  TH  GO 

<N 
8C-  t- 
O  CD 
I—  1 

o  o  o 

irj  O  >O 

TH 

Tf<  CO 

1C  0  TH 

T**  9s  ^ 

fc- 
co 
CO 

CO  CO 

VO  Tj<  O 

CO  00  <N 

CD  CD 
O  t-  OJ 
CO  t-  iH 

1-1  t- 
ua  o  co 

03  t-  TH 

O  00 
O  TH  GO 
<N  CO  O 

t-  OS 
10  TH  •<* 
TH  >0  O 

1—  1  I—I 
O  O  <N 

TH  Tt<  O 

C-  O 

»O  JO  Q 
O  <N  O 

Proportional  Depth 
Velocity 
Discharge  .  . 

pipe,  plus  the  annual  expense  of  pumping,  is  a 
minimum.  With  a  smaller  pipe  the  saving 
in  initial  cost  is  more  than  wiped  out  by  the 
increased  expense  of  pumping ;  while  with  a 
larger  one  the  saving  in  pumping  will  not 


suffice  to  pay  the  interest  on  the  additional 
cost  of  the  pipe. 

VELOCITY  IN  SEWERS. — With  sewers  another 
set  of  considerations  comes  into  play,  namely, 
the  necessity  for  maintaining  such  velocities 
in  them  as  will  prevent  the  formation  of 
deposits.  Du  Buat  and  others  have  made 
careful  observations  of  the  speed  required  to 
keep  various  substances  in  motion,  and  to 
shift  them  again  when  they  come  to  rest. 
Based  on  these  observations,  certain  rules 
have  been  laid  down  as  to  the  rates  of  flow 
which  should  be  maintained  in  sewers  and 
drains.  For  4-in.  and  6-in.  pipes  a  velocity 
of  3  ft.  per  second  is  desirable,  and  for  9-in. 
and  12-in.  sewers  2J  ft. ;  while  for  still  larger 
diameters  2  ft.  per  second  is  regarded  as 
sufficient.  For  this  reason,  and  because  of 
their  greater  hydraulic  mean  depths,  large 
sewers  may  be  laid  with  gradients  very  much 
flatter  than  are  permissible  with  smaller  pipes. 
From  this  fact  a  tendency  has  arisen,  in  cases 
where  fall  is  scanty,  to  employ  larger  sewers 
than  are  called  for  by  the  flow,  for  the  sake  of 
the  flatter  gradients  at  which  it  is  assumed 
that  they  may  be  laid.  The  advantage  thus 
sought  is  wholly  illusory,  since  the  actual 
velocity  in  a  sewer  at  any  gradient  depends, 
not  on  the  size  of  the  pipe,  but  on  the  h.rn.d. 
of  the  stream  flowing  in  it ;  and,  for  any  given 
flow,  the  larger  the  pipe,  the  less,  as  a  rule, 
will  be  the  h.m.d.,  and  consequently  the  less 
the  velocity.  In  arriving  at  the  velocity, 
therefore,  the  depth  of  flow  must  be  taken 
into  account.  Messrs.  Crimp  and  Bruges' 
tables,  already  referred  to,  include  one  giving 
the  proportional  h.m.d.,  velocity,  and  discharge, 
for  depths  of  flow  corresponding  to  every  T^ 
of  the  diameter.  To  take  a  concrete  example : 
a  4-in.  pipe  at  a  gradient  of  1  in  160,  running 
half  full,  will  carry  4'9  cu.  ft.  per  minute 
(44,100  gallons  per  day)  with  a  velocity  of 
1-87  ft.  per  second.  In  larger  pipes,  laid  at  the 
same  gradient,  the  depth  and  velocity  will  be 
as  follows  :— 

6"  pipe,  depth  If",  velocity  1/82  ft.  per  sec. 

9"     „        „      li",      „        1*75     „       „ 
12"     „        „      liY     „        1-68     „       „ 


180 


FLO 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


FLU 


A  12-in.  sewer  would  not  infrequently  be 
used  in  such  a  case,  and  a  4-in.  pipe  at  a 
gradient  of  1  in  160  would  be  regarded  as  out 
of  the  question  ;  yet  the  larger  pipe  would  give 
a  velocity  only  nine-tenths  of  that  which  would 
be  attained  in  the  smaller  one.  The  rate  of 
flow  in  a  sewer  is  in  fact  governed  by  its 
gradient  and  by  the  quantity  of  sewage  flow- 
ing in  it,  and  only  to  a  much  less  extent  by 
its  diameter  ;  and,  so  far  as  the  velocity  is 
affected  by  the  latter,  it  is  almost  invariably 
greater  in  a  small  pipe  than  in  a  larger  one. 

For  various  reasons,  such  as  the  necessity 
for  providing  for  storm-water  or  for  a  future 
increase  of  population,  a  sewer  has  often  to 
be  made  much  larger  than  would  suffice  for 
the  ordinary  dry  weather  flow ;  and  instances 
are  by  no  means  uncommon  in  which  the 
depth  of  flow  does  not  ordinarily  exceed  one- 
tenth  of  the  diameter.  In  such  a  case  the 
velocity  will  be  only  two-fifths  of  that  of  the 
full  pipe,  and,  unless  the  gradient  is  excep- 
tionally steep,  will  be  far  short  of  what  has 
generally  been  supposed  to  be  necessary. 
With  flows  at  the  rate  of  1,800  gallons  per 
day  or  under,  and  gradients  flatter  than  1  in 
20,  1^  ft.  per  second  is  the  highest  velocity 
which  can  be  attained,  and  this  only  in  a 
4-in.  pipe ;  and  a  12-in.  sewer  at  1  in  100  will 
have  a  rate  of  flow  of  2  ft.  per  second  only 
when  carrying  46,000  gallons  per  day  or 
more.  There  are  thousands  of  sewers  all 
over  the  country  in  which  the  flow  is  utterly 
inadequate  to  maintain  the  velocities  which 
are  generally  regarded  as  essential,  and 
which,  nevertheless,  give  perfectly  satisfactory 
results.  This  apparent  discrepancy  between 
the  indications  obtained  by  experiment  and 
the  results  of  practical  experience  is  due  to  a 
variety  of  causes,  among  which  may  be  men- 
tioned the  local  increase  of  velocity  which 
takes  place  wherever  the  waterway  is  narrowed 
by  an  obstruction,  and  which  either  moves 
the  latter  bodily  onward  or  breaks  it  away 
piecemeal. 

Irregularities  in  the  laying  of  the  pipes, 
and  the  intrusion  of  the  jointing  material 
into  them,  play  a  much  greater  part  in  check- 


ing the  flow  in  a  sewer  and  in  causing  deposits 
than  any  reasonable  flatness  of  the  gradient. 
The  velocity  along  the  invert  of  a  sewer  is 
stated  by  Mr.  Baldwin  Latham  to  be  ^  of 
the  mean  velocity.  Wherever  there  is  any 
doubt  as  to  the  self-cleansing  properties  of  a 
sewer,  flushing  should  be  resorted  to.  In 
most  pipe  sewers  the  flow,  especially  near  the 
head  of  the  sewer,  is  liable  to  fall  for  hours 
at  a  time  below  the  minimum  which  can  be 
depended  on  to  prevent  deposit.  It  will, 
therefore,  be  prudent  to  provide  means  for 
flushing  in  every  case.  (See  "  FLUSHING.") 

MAXIMUM  VELOCITY  IN  SEWEKS. — In  large 
sewers,  where  the  depth  of  flow  is  considerable, 
and  large  quantities  of  grit  are  apt  to  be 
present,  it  is  usual  to  limit  the  velocity  to 
about  4  ft.  per  second,  to  avoid  excessive  scour 
on  the  invert.  In  pipe  sewers  6  ft.  per 
second  has  been  mentioned  as  a  maximum  : 
in  practice  such  a  speed  would  only  be 
exceeded  on  very  steep  gradients,  and  with 
flows  much  larger  than  are  ordinarily  met 
with.  Steep  gradients,  have  also  been  objected 
to  on  the  ground  that,  owing  to  the  consequent 
shallowness  of  the  flow,  solid  matter  is  apt  to 
be  left  stranded  in  the  pipe.  Flows  which  are 
insufficient  to  keep  a  steep  sewer  clear  cannot, 
however,  be  relied  on  to  maintain  a  self- 
cleansing  velocity  in  a  flat  one.  A.  J.  M. 

Flushing  Cisterns. — (See  "  WASTE  PRE- 
VENTERS.") 

Flushing      Drains      and      Sewers.— 

Wherever  possible  drains  and  sewers  should 
be  self-cleansing.  This  depends  partly  on 
their  gradients,  but  chiefly  on  the  amount  of 
care  which  is  taken  in  laying  the  pipes  and 
making  the  joints.  For  4-in.  and  6-in. 
drains  3  ft.  per  second  is  regarded  as  a  self- 
cleansing  velocity ;  for  9-in.  and  12-in.  sewers 
2£  ft.  per  second  will  suffice ;  and  for  larger 
diameters  velocities  as  low  as  2  ft.  per  second 
may  be  used.  Where  these  velocities  are 
not  obtained  with  the  ordinary  flow  flushing 
should  be  resorted  to.  Even  when  the  velocity 
is  sufficient  to  prevent  any  actual  obstruction, 


181 


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ENCYCLOPEDIA   OF 


FOO 


flushing  is  still  desirable  for  the  removal  of  the     on  the  market,  all  belonging  to  one  or  two 


accretions  which  take  place  on  the  sides  of  the 
sewer.  It  is  especially  necessary  where  the 
flow  is  small,  as  in  the  upper  lengths  of  a 
sewer,  or  in  districts  not  yet  fully  built  up. 
In  certain  cases  the  provision  of  means  for 
ample  and  frequent  flushing  will  admit  of  the 
use  of  gradients  of  exceptional  flatness. 

Eainwater  is  practically  useless  for  flushing 
purposes,  the  rainfall  being  far  too  uncertain 
to  be  depended  on.  Its  admission  to  the 
sewers,  moreover,  necessitates  the  use  of 
larger  pipes  than  would  otherwise  be  necessary, 
with  a  consequently  sluggish  flow.  So  far  as 
the  drains  from  houses  and  public  institutions 
are  concerned,  the  provision  of  special  means 
for  flushing  can  generally  be  obviated  by 
placing  a  bath  waste  at  the  head  of  each 
principal  drain.  In  sewers  also  the  discharge 
from  an  ejector  or  rising  main  will  often  serve 
to  flush  a  long  sewer.  Where  no  such  means 
are  available  a  penstock  or  valve  is  sometimes 
placed  in  the  sewer  to  head  up  the  sewage  for 
flushing  purposes.  This  plan  is  objectionable 
on  account  of  the  deposits  which  take  place 
behind  the  penstock  when  the  sewage  is  thus 
kept  stagnant,  and,  for  pipe  sewers  at  any 
rate,  proper  flush  tanks  should  be  provided. 
These  may  be  filled  with  sewage  if  there  is  fall 
enough  from  the  feeding  sewer  into  the  one  to 
be  flushed,  but  clean  water  is  preferable. 
Where  the  water  is  obtained  from  the  mains 
the  connections  should  be  trapped,  to  prevent 
the  return  of  air  from  the  sewers.  The  size 
of  the  flush  tank  will  depend  on  the  size  and 
gradient  of  the  sewer,  the  following  being  the 
capacities  usually  employed  :— 

For  a  9-in.  sewer     .  300  to     400  gallons 

»,  12     „         „      .  400  „      600      „ 

„  15     „         „      .  600  „      800      „ 

„  18     „         „      .  800  „  1,000      „ 

and  so  on. 

The  discharge  from  a  flush  tank  may  be 
effected  by  hand,  but  should  generally  be 
automatic.  For  house  drains  tipping  buckets 
may  be  used,  but  where  the  quantity  to  be 
discharged  exceeds  100  gallons,  a  siphon  will 
be  required.  There  are  many  forms  of  siphon 


types.  In  one,  when  the  tank  is  full,  the 
water  falls  over  a  lip,  creating  a  vacuum  in 
the  descending  leg.  In  the  other,  the  air  is 
held  back  by  a  deep  seal,  so  that  the  water  in 
the  tank  ponds  up  over  the  siphon  until  it 
stands  high  enough  to  force  the  air  through 
the  seal,  when  the  siphon  at  once  discharges 
full  bore.  A  good  siphon  will  start  with  a 
drop-by-drop  supply.  A.  J.  M. 

Flushing  Tanks. — Tanks  or  cisterns  con- 
structed to  automatically  discharge  a  certain 
quantity  of  water  at  stated  intervals  for  the 
purpose  of  flushing  drains  or  certain  sanitary 
fittings,  such  as  urinals,  &c.  The  discharge 
of  the  water  is  brought  about  by  either  a 
tipper  or  a  siphon,  fixed  in  the  tank.  The 
timing  of  the  discharges  is  arranged  by  the 
regulation  of  the  tap  through  which  the  tank 
is  filled,  or  by  a  clock  making  electric  contact 
at  certain  hours  and  thereby  releasing  the 
water.  (See  also  "  WASTE  PREVENTERS.") 

Footpaths,   Construction  of.  —  General 
Requirements  and  Width— Foundation  for  Foot- 
ways —  Construction  —  Forms   of  Footpaths  — 
Materials. 

GENERAL  BEQUIREMENTS  AND  WIDTH. — To 
ensure  satisfaction  with  any  class  of  footpath, 
care  must  be  exercised  in  the  choice  of 
materials.  They  should  be  durable,  ensure 
perfect  comfort  and  safety  to  the  pedestrian, 
be  smooth  and  tough  but  not  slippery,  of  fine 
texture  and  uniform  quality  throughout,  and 
they  should  wear  evenly  and  not  flake,  must 
not  absorb  an  abnormal  quantity  of  water,  but 
dry  quickly  after  rain,  should  be  pleasant  in 
colour  and  appearance  and  allow  of  easy 
cleansing.  As  regards  the  width  of  footways, 
the  Local  Government  Board  model  bye-laws 
on  new  streets  suggest  that  each  footpath 
shall  be  not  less  than  one-sixth  the  entire 
width  of  the  street.  In  several  large  provincial 
towns  and  London  boroughs  special  regula- 
tions are  in  force,  and  the  following  which 
govern  the  widths  of  footpaths  in  all  new 


182 


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MUNICIPAL   AND    SANITAEY  ENGINEEKING. 


FOO 


streets  in  the  metropolitan  borough  of  Wands- 
worth  will  be  of  use.  "  In  all  roads  about  to  be 
formed  40  (forty)  feet  in  width,  each  footpath 
to  be  made  8  feet  wide.  In  all  roads  about  to 
be  formed  45  feet  or  50  feet  in  width,  each 
footpath  to  be  made  9  feet  wide."  As  a 
general  rule,  roads  54  ft.  wide  have  footpaths 
10  ft.  6  ins.  wide,  and  roadways  60  ft.  wide 
have  footpaths  12  ft.  wide. 

FOUNDATIONS  FOR  FOOTWAYS.  —  These  are 
usually  of  three  kinds  : — 

1.  Concrete. 

2.  Ashes  or  gravel. 

3.  Hardcore. 

Concrete  foundations  should  be  used  for 
asphalte  pavements  and  under  brick  paving. 
The  depth  varies  from  3  in.  to  4  in.,  but  a 
greater  depth  should  be  given  if  the  footway 
is  liable  to  be  broken  up  for  main  or  service 
pipes  of  any  kind. 

Ashes  or  gravel  foundations  are  used  under 
flag  pavements  and  sometimes  under  brick 
pavements.  The  material  should  be  clean 
and  dry  and  have  a  thickness  of  4  in.  to 
6  in. 

Hardcore  foundations  should  be  provided 
under  all  other  pavements,  especially  tar- 
macadam  and  granite  paving.  The  depth 
varies  from  4  in.  to  6  in.,  and  in  cases 
where  soft  clay  is  found  an  extra  depth  should 
be  allowed.  A  system  adopted  for  the  founda- 
tion under  flag  paving  in  a  South  London 
borough  is  as  follows  : — 

The  ground  is  excavated,  where  necessary, 
to  a  depth  of  8^  in.  The  bottom  layer  is 
composed  of  3  in.  of  good  clean  stone  or 
brick  hardcore  thoroughly  rolled  and  consoli- 
dated. On  the  top  of  the  hardcore  a  layer  of 
ashes  3  in.  in  depth  is  provided,  thoroughly 
rolled  and  watered.  On  the  top  of  the  layer 
of  ashes  artificial  stone  paving  is  laid,  having 
a  mortar  bed  \  in.  in  thickness.  This  method 
has  given  very  satisfactory  results. 

CONSTRUCTION. — All  footways  should  be  laid 
with  a  cross-fall  from  the  back  of  the  footpath 
to  the  kerb  in  towns,  &c.,  and  from  the  kerb 
to  the  back  of  the  footpath  in  the  case  of 
country  roads.  The  following  extract  from 


the  model  bye-laws  of  the  Local  Government 
Board  on  new  streets  gives  useful  informa- 
tion : — "  He  shall  construct  each  footway  in 
such  street  so  as  to  slope  or  fall  towards  the 
kerb  or  outer  edge  at  the  rate  of  one  half  of 
an  inch  for  every  foot  in  width,  if  the  footway 
be  not  paved,  flagged  or  asphalted ;  and  at 
the  rate  of  not  less  than  a  quarter  of  an  inch 
and  not  more  than  one  half  of  an  inch  in  every 
foot  in  width  if  the  footway  be  paved,  flagged 
or  asphalted." 

The  Municipal  Engineers'  Specification  gives 
the  following  cross-falls  : — 

£  in.  per  foot  of  width    for  asphalte. 

,  flags  (natural  and 

artificial). 
,  concrete  in  situ. 
,  tar  matrix. 
,  cement  matrix, 
bricks,  macadam. 


The  cross-fall  should  be  allowed  in  the 
foundation,  the  material  being  laid  of  uniform 
thickness.  The  kerb  should  be  laid  first  on 
concrete  6  in.  in  depth,  and  show  a  channel, 
as  suggested  by  the  model  bye-laws  of  the 
Local  Government  Board,  not  less  than  3  in. 
in  the  shallowest  part  and  not  more  than 
7  in.  in  the  deepest  part.  It  has  been  found 
in  times  of  heavy  rains  that  the  gully  gratings 
get  choked  with  dead  leaves,  and  much  water 
passes  beyond  the  gully.  To  prevent  this, 
overflows  should  be  cut  in  the  kerb  over  each 
gully  about  1  ft.  9  in.  to  2  ft.  in  length. 
Where  carriage  entrances  occur  in  the  foot- 
path it  is  usual  to  construct  them  in  either 
of  the  following  ways : — 

1.  The  kerb  is  dropped  to  within  an  inch 
of  the  channel  for  the  width  of  the  carriage 
entrances,  and  the  materials  (either  granite 
setts,    cubes,  or  blue    bricks,    &c.)    are   laid 
butting  against  the  paving  material  of   the 
footway. 

2.  No  kerb  is  laid  in  front  of  the  carriage 
entrance,  but  the  paving  material  is  laid  up 
to  the  channel.      Instead  of  the   setts,  &c., 
butting   against  the  flags  of  the  footpath,   a 
return  edge  kerb  6  in.  in  width  is  laid  from 


183 


FOO 


FOO 


the  outer  kerb  to  the  forecourt  fence  or  wall. 
In  each  case  the  carriage  entrance  is  laid  at 
the  same  level  as  the  remainder  of  the  foot- 
way, except  near  the  edge  where  it  com- 
mences to  dip  to  meet  the  channel.  The 
footway  kerb  on  each  side  of  the  carriage 
entrance  is  bullnosed. 

FORMS  OF  FOOTPATHS. — There  are  two  forms 
of  footpaths, 

1.  Macadam. 

2.  Paved. 

1.  MACADAM. — The  first  is  used  for  country 
roads  and  villages,    but  is  not  to  be  recom- 
mended.     The   disadvantages   are   many  : — 

(a)  The  material  becomes  loose  with  traffic  ; 

(b)  the  paths  are  muddy  in  wet  weather  and 
very   dusty    in    dry   weather ;    (c)    they   are 
uneven  on  the  surface,  and  require  constant 
repairs.     This  class  of   footpath  is  certainly 
an  advance  on   the  bare  earth,  and  is  con- 
structed by  laying  a  covering  of  gravel,  engine 
ashes,  or  other  similar  material  about  3  or  4  in. 
deep  on  the  top  of  the  earth,  it  being  then 
well  watered  and  rolled  to  a  solid  formation. 

2.  PAVED   FOOTWAYS. — There    are   a    great 
many  materials  used  in  this  form  of  pave- 
ment, among  them  being  :— 

Natural  stone  flags. 

Artificial  stone  flags. 

Concrete  of  various  kinds. 

Tar  paving. 

Bricks. 

Asphalte. 

Various  combinations  of  the  above. 

MATERIALS. — 1.  NATURAL  STONE. — There  are 
many  quarries  from  which  natural  stone  may 
be  obtained,  but  are  too  numerous  to  mention 
in  detail  in  this  article.  Yorkshire  stone  is 
largely  used,  and  is  very  tough  in  fibre  and 
wears  well  if  properly  selected.  Natural  stone 
flags  should  not  be  less  than  2£  in.  in  thickness, 
and  should  be  bedded  and  jointed  with  cement 
mortar.  The  price  of  the  stone  varies  in 
different  districts  from  5s.  to  8s.  &d.  per  super- 
ficial yard,  including  the  foundation.  The 
price  in  London  for  2  in.  thick  ranges  from 
4s.  3f/.  to  5s.  3fZ.  per  superficial  yard,  and  when 
laid,  from  5s.  3d.  to  6s.  3d.  per  superficial  yard. 


ARTIFICIAL  STONE. — The  patent  stone  flags  on 
the  market  are  too  numerous  to  mention,  and 
only  a  few  will  be  touched  upon.  Each  stone 
should  be  laid  to  break  the  joint  6  in.  A 
few  makes  are  Victoria,  Aberdeen  Adamant, 
Croft,  Imperial,  Excelsior,  Atlas,  Nonslip 
(hard  York)  stone.  The  advantages  of  this 
class  of  paving  are  :  Less  cost,  even  surface, 
durability,  square  edges,  regular  sizes ;  and 
the  disadvantages  are :  Tendency  to  become 
slippery  in  wet  weather  and  under  the  heat  of 
the  sun,  liable  to  easily  break  if  bedded 
unevenly,  somewhat  dazzling  in  the  sun, 
when  lifted  by  a  pick  for  repairs  are  liable  to 
chip.  The  cost  differs  considerably,  but,  as  a 
guide,  varies  from  4s.  6d.  to  6s.  6d.  per  super, 
yard  laid.  The  cost  at  the  works  is  as 
follows  : — 

Victoria  2  in. 


21  in. 


.  3s.  6c7.  per  yard  super. 

.  4s.  6d.      „      „ 
Nonslip          (hard 

York)  2  in.         .  5s.  6d.      ,,      ,,         ,, 

Imperial  2  in.        .  5s.  9d.      ,,      ,,         ,, 

CONCRETE  IN  SITU  PAVING. — These  pavements 
are  generally  composed  of  granite  chippings 
and  Portland  cement,  in  the  proportion  of  4 
of  chippings  to  1  of  cement  for  the  bottom 
layer,  and  1  of  chippings  to  1  of  cement  for 
the  top  layer,  having  a  total  depth  of  about 
1£  in.  to  2  in.  When  laid  in  long  lengths 
this  paving  cracks  very  considerably,  and 
wood  screeds  should  be  laid  down  dividing 
the  paving  into  bays  about  4  ft.  to  6  ft. 
in  length  and  the  full  width  of  the  footpath. 
Alternate  bays  are  laid  and  allowed  to  set 
before  the  intermediate  bays  are  filled  in.  To 
give  a  better  foothold,  these  are  either  grooved 
or  indented  by  rolling  with  a  grooved  or  spiked 
hand -roller.  They  are  difficult  to  repair,  can 
only  be  laid  after  the  frosty  season,  and  take 
considerable  time  to  execute,  but,  on  the  other 
hand,  have  few  joints.  Several  firms  make  a 
speciality  of  this  class  of  paving,  laying  it  at  a 
fixed  price  per  square  yard,  and  guarantee  to 
maintain  it  for  certain  periods  of  time,  and  for 
this  reason  the  work  is  best  left  to  them  to 
execute. 


184 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


FRE 


TAR  PAVING. — This  paving  is  composed  of  a 
bottom  layer  of  tarred  granite  chippings  about 
1  in.  in  diameter  rolled  down  to  a  thickness 
of  2  in.  This  coat  is  then  left  open  to 
traffic  for  a  period  of  about  a  week.  The 
surface  is  then  swept,  and  the  top  layer,  con- 
sisting of  tarred  chippings  about  \  in.  to 
f  in.  in  diameter,  is  then  laid  and  rolled 
to  a  thickness  of  about  1  in.  This  is  then 
covered  with  crushed  shell  and  sand.  The 
cost  works  out  at  about  2s.  Qd.  per  superficial 
yard. 

BRICKS. — These  are  largely  used  as  paving 
materials,  and  form  very  durable  surfaces. 
They  are  laid  on  a  bed  of  concrete,  varying 
from  3  in.  to  4  in.  in  thickness  in  hori- 
zontal or  diagonal  rows.  A  very  effective 
form  of  paving  is  obtained  by  having  a  centre 
portion  about  4  ft.  wide  laid  in  red  bricks 
and  the  margins  on  either  side  laid  with 
Kentish  rag  spalls  about  4  in.  deep,  all 
laid  on  concrete.  The  cost  of  this  works 
out  at  about  9s.  per  yard  super.,  including 
foundation,  using  red  sand  bricks. 

ASPHALTE. — This  form  of  pavement  is  laid 
in  exactly  the  same  manner  as  for  roadways, 
the  price  being  the  same.  It  is  slippery  and 
dangerous  in  wet  and  hot  weather.  The 
foundations  for  the  above  pavements  have  been 
dealt  with  in  the  first  part  of  the  article. 

F.  L.  and  R.  H.  B. 

Footways. — (See  "ROADS  AND  STREETS.") 

Forced     and     Induced      Draught.— 

Mechanical  draught,  whether  "  forced "  or 
"induced,"  enables  a  higher  temperature  to 
be  obtained  in  a  furnace,  and  therefore 
increases  its  capacity.  It  also  permits  the 
use  of  inferior  fuels.  Several  systems  of 
forced  draught  are  in  use  ;  one  consists  of  a 
closed  stokehold  into  which  air  is  forced  by 
means  of  a  fan ;  thus  a  greater  quantity  passes 
through  the  furnace  than  would  obtain  with 
natural  draught.  Under  this  system  the 
stoker  of  necessity  works  in  a  pressure  above 
that  of  the  atmosphere,  and  the  compartment 


185 


can  only  be  entered  or  left  through  an  air 
lock. 

Another  plan  (Howden's)  is  to  use  a  closed 
ashpit  and  a  special  fire-door,  to  both  of  which 
air,  previously  heated,  is  conveyed,  the  supply 
to  the  ashpit  being  at  a  lower  pressure  than 
that  to  the  fire-door.  The  act  of  opening  the 
fire-door  automatically  shuts  off  the  supply. 

In  Meldrum's  well-known  system  the 
ordinary  firing  arrangements  are  retained,  but 
the  ashpit  is  closed.  Two  bell-mouthed  pipes 
project  into  the  space  below  the  firebars,  and 
in  each  pipe  there  is  a  steam  jet,  the  blast 
from  which  forms  an  air  injector  and  so  pro- 
motes combustion.  This  system  can  be  applied 
to  any  kind  of  boiler  or  the  furnace  of  a 
refuse-destructor. 

The  simplest  example  of  induced  draught 
(other  than  that  due  to  a  chimney)  is  that  in 
use  in  locomotive  and  portable  engine-boilers 
— in  this  case  the  exhaust  steam  is  discharged 
into  the  base  of  the  chimney — the  orifice  of 
the  blast  pipe  being  usually  placed  just  above 
the  top  row  of  tubes.  Mechanically  induced 
draught  is  effected  by  employing  a  suction  fan 
to  draw  the  waste  gases  from  the  flue  and 
discharge  them  into  the  smoke  stack. 

Other  advantages  of  mechanical  draught  are 
that  the  chimney  need  only  be  high  enough  to 
disperse  the  waste  products  and  to  fulfil  local 
requirements.  It  also  admits  of  regulation, 
automatically  or  otherwise,  to  very  varying 
demands,  and  is  independent  of  climatic 
conditions. 

Both  systems  have  their  advocates.  The 
choice,  however,  depends  partly  on  local 
circumstances.  (See  "  BOILERS,  CHIMNEYS.") 

E.  L.  B. 

French  Drains  are  trenches  or  grooves 
filled  with  rubble,  stone,  chalk,  or  large  gravel 
to  allow  water  to  pass  away  freely.  At  the 
back  of  a  retaining  wall  in  a  wet  soil  French 
drains  are  put  in  vertically  at  intervals  of 
about  10  ft.,  with  a  weep  hole  about 
3  in.  diameter  through  the  wall  at  the  foot 
of  each  drain,  to  carry  off  the  water  and 
prevent  an  increase  of  thrust  by  hydrostatic 


FRO 


ENCYCLOPEDIA   OF 


FUE 


pressure  at  the  back  of  the  wall.  In  draining 
land  by  this  means  the  trenches,  about  2  ft. 
deep,  have  inclined  sides  with  the  bottom 
filled  in  with  rubble,  chalk,  or  gravel,  and 
covered  with  straw  or  brushwood  to  prevent 
choking ;  the  soil  is  then  returned  to  fill  the 
remainder  of  the  depth,  say  a  foot,  and  lightly 
rammed  to  consolidate  it. 

Frost. — EFFECT  ON  WATER  PIPES  AND 
SANITARY  FITTINGS. — Water  at  a  tempera- 
ture of  32°  F.,  or  freezing  point,  congeals 
and  forms  into  a  solid  mass  known  as 
ice.  At  the  moment  of  so  doing  it  expands 
at  great  force.  It  is  this  action  which 
causes  frost-burst  in  water  pipes  that  have 
not  been  properly  protected,  although  the 
effects  are  not,  as  a  rule,  noticed  until 
the  advent  of  a  thaw.  Various  materials 
resist  frost-burst  to  different  degrees.  Lead 
pipes  offer  small  resistance,  but  will  frequently 
expand  or  bulge  out  sufficiently  to  prevent 
fracture.  Cast-iron  pipes,  although  stronger, 
are  readily  split  from  end  to  end.  Wrought- 
iron  pipes  resist  fracture  better  than  either  of 
the  foregoing,  but  are  also  frequently  split. 

Hot-water  pipes  exposed  to  frost  suffer  no 
less  than  cold-water  pipes,  and  the  effect  may 
be  much  more  serious,  as  the  blockage  of  the 
pipes  by  ice  may  lead  to  boiler  explosions, 
either  by  causing  excessive  steam  pressure,  or 
by  the  sudden  admission  of  cold  water  to  an 
overheated  boiler.  Similarly,  explosions  may 
be  caused  by  frozen  expansion  pipes  which 
are  gradually  blocked  by  ice  formed  from 
condensation  in  the  pipes. 

The  prevention  of  frost  in  water  pipes  lies 
in  protecting  the  pipes  against  frost  by  placing 
them  in  frost-proof  positions  or  by  encasing 
them  in  non-conductive  materials  where  ex- 
posed. Wrapping  the  pipes  in  several  layers 
of  brown  paper  pasted  down  will  frequently 
suffice.  Other  suitable  materials  for  protection 
are  sawdust,  cork  chips,  hair  felt,  plaster  of 
Paris,  asbestos,  slag  wool  and  boiler  com- 
positions. The  effect  of  frost  on  sanitary 
fittings  is  less  serious  than  on  water  pipes, 
leading  merely  to  the  temporary  disuse  of  the 


fittings  affected.  In  most  cases  the  trouble  is 
caused  by  leaking  taps,  the  water  from  which 
freezes  in  the  waste  pipes  and  gradually  blocks 
them.  W.  M. 

Fuel. — Combustion  is  a  rapid  chemical 
combination  accompanied  by  the  evolution  of 
heat  and  usually  light.  The  chief  supporter 
of  combustion  is  the  oxygen  contained  in  the 
air,  and  all  bodies  which  burn  in  air  burn 
with  greater  brilliancy  in  oxygen  gas.  The 
quantity  of  air  required  for  the  complete 
combustion  of  different  fuels  varies,  but 
should  in  each  case  be  correctly  apportioned. 
Insufficient  air  prevents  complete  combustion 
and  produces  smoke,  but  an  excess  of  air 
causes  waste  of  heat  as  it  needlessly  lowers 
the  temperature  of  the  flue  gases. 

If  the  composition  of  a  fuel  is  known  the 
heat  evolved  by  its  combustion  can  be  cal- 
culated. The  fuels  mostly  used  are  those 
substances  containing  large  proportions  of 
carbon  and  hydrogen,  such  as  coal,  charcoal, 
coke,  peat  and  wood,  and  the  liquid  and 
gaseous  fuels,  the  most  important  of  which 
are  the  mineral  oils  and  coal  gas. 

The  comparative  value  of  the  principal  fuels 
in  British  thermal  units  is  as  follows  : — 


Fuel. 

Evaporative 
Power  from 

British 
Thermal 

Relative 
Carbon 

212°  F. 

Units. 

Value. 

Carbon 

15-0 

14,500 

1-00 

Charcoal  (wood) 

12-4 

12,000 

•83 

Coke  (average) 

13-5 

13,000 

•89 

Welsh  Coal  (average) 

15-3 

14,800 

1-02 

Petroleum     (average) 

20-7 

20,000 

1-38 

Coal     Gas     (average) 

21-7 

21,000 

1-45 

The  ordinary  comparative  power  of  Welsh 
steam  coal  from  100°  F.  of  feed-water  is  from 
10  to  11  Ibs.  of  water  per  Ib.  of  coal.  In 
the  choice  of  a  coal  for  pumping  purposes 
the  principal  point  to  consider  is  the  selection 
of  that  class  which,  upon  the  average  of  a 
series  of  tests,  evaporates  a  given  quantity  of 
water  from  a  given  temperature  at  the  lowest 
cost.  From  the  steam  user's  point  of  view 
this  consideration  practically  embraces  the 


186 


FUE 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


GAS 


whole  matter  and  will  determine  his  decision. 
A  careful  commercial  test  of  the  various  coals 
that  may  be  under  consideration  should    be 
made  by  evaporating  a  certain  known  quantity 
of  water  in  the  same  boiler  by  each  of  the 
different  fuels  in  turn,  taking  special  care  that 
all  the  influencing  conditions  of  the  test  are 
similar  in  every  case,  so  that  all  may  be  on 
the  same  basis  as  near  as  practicable.     If  the 
fires  be  not   drawn  between  each  test,  they 
should  at  least  be  in  the  same  condition  as 
near  as  possible,  the  feed-water  should  be  of 
the  same  temperature,   or  proper  allowance 
made,    the   quantity   passed   into    the   boiler 
should  be  accurately  weighed  and  the  water- 
level  left  the  same  at  finish  as  it  stood  at  the 
start  of  the  test ;  the  total  coal  used  must  also 
be  weighed,  and  the  percentage  of  ash  ascer- 
tained.     It  is  also   important    to    note    any 
variation  of  draught  in  each  case,  to  observe 
the  amount  of  smoke  produced,  differences  in 
stoking,  and  the  nature  and  amount  of  the 
clinker  and    ash.     From  such  a  test  it  will 
oftentimes  be  found  that  the  cheapest  coal  is 
by  no  means  the  most  economical  to  use.     In 
the  coal-mining  districts  of  the  Midlands  and 
North  of  England,  and  at  places  where  the  cost 
of  freightage  is  light,  it  is  often  found  economical 
to  use  a  low  class  of  fuel  which  may  be  had  at 
the  pits'  mouth  for  a  few  shillings  per  ton,  but 
in  the  South-East  of  England,  where  the  cost 
of  carriage  from  the  mining  districts  is  heavy, 
it  is  as  a  rule  more  economical  to  use  the  best 
class  of  fuel  "than  to  pay  the  heavy  carriage 
rates  on  a  low  class  material,  a  large  percentage 
of  which  will  result  in  ashes.     This  question 
of  high-class  versus  low-class  fuels  is  one  of 
great  practical  importance,  and  is  worthy  of 
the  careful  consideration  of  every  engineer  in 
the  light  of  the  special  circumstances  of  his 
own  case. 

Of  oil-fuels,  a  large  quantity  of  that  now 
available  in  this  country  comes  from  the 
newly  opened  Beaumont  field  in  Texas.  It 
will  evaporate  about  15  Ibs.  of  water  per 
pound,  has  a  specific  gravity  of  "925  at  60°  F., 
a  flash  point  of  185°  F.  (Abel  test),  and 
ignites  at  200°  F.  Its  average  calorific  value 


is  19,500  British  thermal  units.  Texas  and 
Roumanian  cheap  oils  are  now  largely  used  in 
oil-engines  for  motive  power  purposes,  in  loco- 
motives, and  also  in  stationary  boilers. 

Gas. — Gas  Supply — Manufacture — Distribu- 
tion —  Public  Street  Lighting  —  Domestic  and 
Trade  Uses — Water  Gas. 

GAS   SUPPLY. — The   supply   of   gas   in   the 
United  Kingdom  is  a  business  carried  on  as  a 
virtual  monopoly,  and,  in  the  case  of  all  large 
undertakings,  also   under   the   protection   of 
private  Acts  of  Parliament.      There  is  never 
an  expressed  guarantee  against  competition  ; 
but  this  is  implied  by  the  law  and  rests  upon  the 
necessities  of  the  business  and  the  consideration 
of  public  convenience,  as  there  cannot  advan- 
tageously be  two  sets  of  gas  mains  in  different 
ownership  in  the  same  street.     Some  small 
country  gas  companies  have  no  special  Act, 
and  therefore  depend  upon  maintaining  a  good 
understanding  with    the  highway  authority, 
without  which  they  could  not  lay  a  main  or 
touch   a  pipe  already   burie'd   underneath  a 
public  road.    Private  and  public  gas  Acts  give 
this  power,  requiring  in  return  certain  con- 
ditions of  the  undertakers  as  regards  limitation 
of  profits,   sliding  scale  of  selling  price  and 
dividends,  quality  of  the  gas,  and  obligation  to 
supply  on  demand.     Gas  property  is  freehold. 
It  is  not  usual  to  grant  local  authorities  power 
to   purchase   gas   undertakings   without    the 
consent  of  the  proprietors ;  although  this  is 
sometimes  done  on  proof  of  expediency  being 
given.      The   opportunity   of   obtaining  pur- 
chasing  power    ordinarily   arises   when    the 
company     promotes    a    Bill    for    fresh    and 
additional  powers,  such  as  are  calculated  to 
enhance  the  value  of  the  undertaking.    Muni- 
cipal gas  committees  succeed  to  all  compatible 
powers  and  obligations  of  the  gas  company. 
The   general   English   law   of  gas   supply  is 
contained    in    the    following    statutes :    The 
Lighting  and  Watching  Act,  1883  ;  Gasworks 
Clauses    Act,    1847 ;      Towns    Improvement 
Clauses  Act,  1847;  Sale  of  Gas  Acts,  1859-60; 
Gas  and  Water  Facilities  Act,  1870,  Amend- 
ment Act,  1873  ;  Gasworks  Clauses  Act,  1871  ; 


187 


GAS 


ENCYCLOPAEDIA   OF 


GAS 


Public  Health  Act,  1875 ;  Conspiracy  and 
Protection  of  Property  Act,  1875 ;  Public 
Works  Loans  Act,  1875  ;  Burghs  Gas  Supply 
(Scotland)  Act,  1876 ;  Public  Health  (Ireland) 
Act,  1878  ;  and  Amendments  Acts. 

MANUFACTURE. — The  town  gas  distributed  in 
the  United  Kingdom  is  chiefly  composed  of 
the  gaseous  distillate  from  bituminous  coal, 
carbonised  in  closed  fire-clay  retorts  at  a  tem- 
perature of  1,800°— 2,000°  F.  For  economical 
reasons  this  coal  gas  is  in  many  places  supple- 
mented with  a  proportion  of  carburetted  or 
"  blue  "  water  gas  (see  article,  "  WATER  GAS  "). 
In  good  working,  about  11,500  cu.  ft.  of 
gas  should  be  made  from  a  ton  of  good  coal, 
the  choice  of  which  depends  upon  geographical 
and  transportation  considerations.  Towns  on 
or  near  the  eastern  and  southern  seaboard, 
including  London,  use  chiefly  the  strongly- 
coking  coals  of  Northumberland  and  Dur- 
ham; with  occasional  or  partial  supplies  of 
railway-borne  coals  from  Yorkshire,  Derby- 
shire, Nottinghamshire  or  North  Wales.  The 
quality  of  gas  is  expressed  in  terms  of  the 
luminous  intensity,  in  the  equivalent  number 
of  standard  sperm  candles  of  six  to  the  pound, 
of  a  flame  burning  at  the  rate  of  5  cu.  ft. 
per  hour,  as  measured  by  the  photometer 
under  statutory  conditions.  The  gas  of  the 
Metropolis  and  the  South  of  England  generally, 
as  well  as  abroad,  wherever  the  Durham  gas 
coal  goes,  is  rated  at  from  14  to  16  candle- 
power.  The  tendency  is  in  favour  of  a  still 
lower  figure,  because  this  manner  of  stating 
the  "  quality "  of  town  gas  is  obsolete  and 
does  not  correspond  with  modern  uses  of  the 
commodity.  What  is  classified  as  14-candle 
gas  yields  on  the  same  basis  of  consumption, 
with  the  incandescent  (Auer,  or  Welsbach) 
"  mantle,"  100  candle-light.  Gas  of  higher 
oaridle-power  with  the  luminous  flame,  does 
not  yield  a  proportionally  better  light  by  the 
incandescent  system. 

Other  saleable  products  of  the  distillation 
of  coal  for  gas-making  are  coke,  tar,  and 
ammoniacal  liquor.  Sometimes  cyanogen 
salts  are  also  recovered.  The  gas  being  the 
principal  product,  which  must  be  made  in 


quantity  to  supply  the  daily  demand,  the 
other  products  of  manufacture  are  classified  as 
"  residuals,"  or  by-products,  the  market  value 
of  which  goes  to  reduce  the  prime  cost  of  tin 
gas  in  the  holder.  The  crude  gas  as  it  comes 
from  the  retorts  is  laden  with  the  vapours  o: 
tar  and  ammoniacal  liquor,  which  condense  ir 
due  course,  and  is  charged  with  the  gaseous 
impurities,  sulphuretted  hydrogen,  ammonia 
and  carbonic  acid.  The  first  is  removable  bj 
means  of  oxide  of  iron  or  slaked  lime  ;  the 
second  by  washing  with  water,  with  recover} 
of  the  ammonia  ;  the  third  is  often  left  in  bul 
is  otherwise  removable  by  slaked  lime 
When  oxide  of  iron  is  used  to  absorb  the 
sulphuretted  hydrogen,  the  sulphur  is  re- 
covered in  saleable  form.  Some  sulphui 
impurity,  in  other  forms  than  the  offensive 
sulphuretted  hydrogen,  always  remains  in  coa' 
gas,  the  quantity  ranging  from  20  to  50  grains 
in  100  cu.  ft.,  according  to  the  nature  oi 
the  coal  and  the  temperature  of  carbonisation, 
This  sulphur  is  supposed  to  exist  partly  in 
undetected  organic  forms  without  cheniica' 
affinity,  and  consequently  irremovable  bj 
chemical  treatment,  and  partly  (in  the  case 
of  gas  made  at  a  high  temperature)  as  bisul- 
phide of  carbon.  In  whatever  forms  the 
sulphur  may  exist  in  gas,  it  burns  to  sul- 
phurous acid.  After  purification,  and  being 
measured,  for  administrative  reasons,  gas  is 
stored  in  sheet-iron  holders  over  water.  Ample 
storage  capacity  is  a  great  aid  to  economy  in 
working.  The  gas-holders  should  always  be 
of  a  capacity  equal  to  one  day's  (24  hours) 
maximum  output. 

DISTRIBUTION. — The  weight  of  the  holdei 
gives  the  pressure  at  which  the  gas  is  sent  out 
for  distribution  through  the  town  mains  and 
house  services.  This  weight  is  lifted,  on  the 
manufacturing  side,  by  mechanically  driven 
"exhausters" — so  called  because  they  draw 
off  the  gas  from  the  retorts,  and  force  it 
onwards  through  the  purifying  apparatus 
into  the  holders.  The  pressure  of  the  holders, 
on  the  outlet  side,  is  regulated  by  "governors." 
These  control  the  town  supply  according  to 
the  demand,  irrespective  of  any  varying 


188 


GAS 


MUNICIPAL   AND    SANITAKY  ENGINEERING. 


GAS 


pressure  exerted  by  the  holders,  which  differ  in 
capacity  and  weight.  Sometimes  the  weight 
of  the  holder  is  insufficient  to  give  the  required 
pressure,  when  the  difficulty  can  be  met  by  the 
use  of  a  "  booster  "  fan.  Registering  pressure 
indicators  should  be  kept  to  show  the  amount 
of  the  initial  pressure  at  the  works  outlet 
mains,  and  also  at  critical  localities  in  the 
district  of  supply.  The  law  requires  gas  mains 
and  services  to  be  kept  constantly  charged 
under  pressure  (Gasworks  Clauses  Act,  1871, 
clause  11 ;  Burghs  Gas  Supply  (Scotland)  Act, 
1876,  clause  56).  This  pressure  is  not  to  be 
less  than  will  balance  the  weight  of  a  column 
of  water,  from  midnight  to  sunset,  six-tenths 
of  an  inch  high,  and  eight-tenths  of  an  inch 
high  from  sunset  to  midnight.  Such  a  mini- 
mum pressure  was  sufficient  at  the  date  of  the 
passing  of  the  Acts,  when  the  sole  use  of  gas 
was  for  lighting  by  means  of  flat  flame  or 
Argand  luminous  flame  burners,  which  were 
low  pressure  appliances,  working  most  satis- 
factorily at  five-tenths  pressure.  It  is  in- 
adequate now,  when  the  greater  part  of  gas 
sold  is  used  for  fuel  purposes,  and  by 
means  of  incandescent  lighting  burners,  all  of 
which  require  a  pressure  of  not  less  than 
fifteen-tenths  at  the  point  of  ignition.  There- 
fore the  minimum  permissible  pressure  of  gas 
in  the  street  mains  night  and  day  should  be 
not  less  than  twenty-tenths,  or  2  in.  of 
water ;  and  this  pressure  should  be  available 
all  over  the  district  of  supply,  irrespective  of 
repair  operations,  &c.  Trunk  gas  mains  may 
be  of  cast-iron  or  steel,  jointed  by  means  of 
spigots  and  sockets,  with  rope-yarn  and  lead, 
or  with  turned  and  bored  joints.  If  of  steel 
they  maybe  welded, or  of  drawn  tube.  Mains 
in  roadways  should  be  2  ft.  6  in.  deep  to 
the  top  of  the  sockets,  and  are  most  con- 
veniently laid  about  3  ft.  from  the  kerb.  Gas 
mains  must  not  be  laid  nearer  to  a  water  main 
than  4  ft.,  and  must  cross  such  mains,  if 
necessary,  at  a  right  angle  (Lighting  and 
Watching  Act,  1833).  It  is  the  modern  prac- 
tice to  supply  houses  in  streets  from  "  service 
mains,"  laid  at  a  depth  of  12  in.  underneath 
each  side  pavement,  for  convenience  of  access. 


No  main  less  than  4  in.  in  diameter 
should  be  put  underground.  In  a  few  large 
cities  street  subways  for  gas  and  water  mains, 
electric  cables,  &c.,  exist  under  new  thorough- 
fares, but  their  construction  is  not  generally 
favoured  for  old  roads.  Mains  must  have  a 
fall  of  T^o  to  siphon  traps  for  condensed 
water.  House  services  are  usually  of  iron, 
with  a  few  exceptions  in  favour  of  lead  pipe. 
A  good  quality  of  steam  piping, painted,  should 
be  used.  Gas  mains  are  best  tapped  on  the 
side,  and  the  service  pipe  should  never  be 
smaller  than  1  in.  for  ordinary  frontage 
lengths.  It  must  be  laid  with  a  fall  towards 
the  main.  Owners  or  occupiers  of  any 
premises  situate  within  25  yards  from  a  main 
are  entitled  to  a  supply  of  gas,  on  paying  for 
all  service  piping  beyond  the  first  30  ft.,  and 
entering  into  a  written  contract  if  required 
(Gasworks  Clauses  Act,  1871,  clause  11  et  seq.)~ 
The  supply  must  be  by  meter,  if  required  by 
the  undertakers,  who  must  provide  the  meter 
(on  demand)  according  to  the  Sale  of  Gas 
Act,  1860.  The  register  of  such  meter  is 
primd  facie  evidence  of  the  quantity  of  gaa 
consumed,  subject  to  appeal  to  two  justices. 
Payment  for  gas  may  in  certain  circumstances 
be  demanded  in  advance,  or  security  may  be 
required.  Such  security,  if  in  cash  deposited, 
is  not  an  advance  payment.  Interest  is 
payable  on  cash  deposits.  The  supply  of 
prepayment  meters,  stoves,  and  gas  fittings  is 
not  compulsory.  The  amount  of  gas  bills, 
including  meter  hire,  is  recoverable  by  sum- 
mary process  before  justices.  Private  Acts 
usually  provide  against  gas  stoves,  &c.,  being 
taken  under  distress  for  rent ;  and  also  limit 
the  period  of  error  for  defective  meters  to  the 
current,  or  preceding  quarter. 

PUBLIC  STREET  LIGHTING. — The  supply  of 
gas  to  public  lamps  is  compulsory  on  demand 
at  a  price  settled  by  agreement  when  not 
specified  by  the  special  Act.  It  is  usually 
taken  on  the  basis  of  the  lowest  price  charged 
to  any  private  consumer  for  lighting.  The 
posts,  lanterns,  and  burners  are  usually  the 
property  of  the  consumer,  whether  a  public 
authority  or  any  person  requiring  a  street 


189 


GAS 


ENCYCLOPAEDIA   OF 


GAS 


lamp.  Lighting,  cleaning,  and  repairing  are 
ordinarily  contracted  for  with  the  gas  company 
at  intervals  of  3  or  5  years.  Painting  is 
separate.  A  schedule  of  hours  of  lighting  and 
extinguishing,  based  on  local  time,  forms  part 
of  the  contract.  "  Moonlight  schedules  "  are 
only  favoured  for  rural  districts.  The  exten- 
sion of  compulsory  services  to  public  street 
lamps  is  for  50  yards  from  an  existing  main. 
(A  main  is  a  pipe  supplying  two  or  more  con- 
sumers.) The  supply  of  gas  to  public  lamps 
may  be  on  the  average  meter  system,  with  a 
meter  to  every  10  or  12  lamps,  but  since 
incandescent  lighting  has  been  in  vogue  this 
system  has  generally  been  abandoned  as  a 
needless  expense.  Street  lamps  may  have 
governors  fixed  to  them  at  the  expense  of 
either  party  (Gas  Works  Clauses  Act,  1871, 
clauses  24  to  27).  Anti-vibrators  are  usually 
required  for  incandescent  street  lamps  in  busy 
thoroughfares  to  economise  •  mantles.  Ordi- 
nary old-fashioned  street  lamp-posts  and 
lanterns  cannot  be  satisfactorily  converted  to 
the  incandescent  lighting  principle,  for  which 
strong,  steady  posts  and  wind-proof  lanterns 
are  necessary.  The  capital  cost  of  new  posts, 
lamps,  &c.,  is  recouped  by  the  annual  saving 
in  gas  consumed,  which  is  only  3£  to  4 
cu.  ft.  per  hour  with  Welsbach  "  C  "  or  Kern 
No.  4  burners,  or  Sugg's  or  Bray's  equiva- 
lents, as  compared  with  5  cu.  ft.  per  hour 
with  the  old  flat  flames.  With  an  average 
yearly  lighting  period  of  4,000  hours  the  differ- 
ence quickly  mounts  up.  There  is  a  partial 
set-off  in  the  cost  of  mantles,  of  which  from 
5  to  12  yearly,  or  more  in  roads  with 
heavy  traffic  may  be  required.  This  com- 
parison sets  no  value  on  the  increased  brilliancy 
of  incandescent  lighting,  which  is  represented 
by  the  proportion  80  to  12  in  direct  candle- 
power  intensity.  A  lamp-renewal  fund  should 
be  maintained  by  every  local  gas  authority  so 
as  to  enable  the  fixtures  to  be  kept  up  to  date. 
Nothing  gives  a  worse  impression  than  to  see 
an  insufficient  number  of  street  lamps,  ill-kept 
lanterns,  and  poor  mantle  maintenance.  Posts 
in  rural  roads  may  be  spaced  80  yards  apart, 
and  more  thickly  according  to  the  density  of 


the  traffic.  Streets  over  50  ft.  wide  between 
frontages  should  have  double  burners,  of 
which  one  could  be  extinguished  at  midnight. 
Wide  boulevards,  open  places  and  squares,  the 
processional  approaches  to  public  buildings, 
docks,  and  large  railway  stations,  are  best 
lighted  by  high-pressure  gas  in  powerful  units. 
The  extra  cost  of  gas  compression  for  this 
purpose  is  about  Id.  per  1,000  cu.  ft.,  and 
its  efficiency  is  doubled  or  trebled  according 
to  the  system  adopted.  Parliament  Square, 
Parliament  Street,  and  other  centres  of  metro- 
politan traffic  are  always  kept  up  to  the  latest 
style  of  good  street  lighting.  There  are  several 
mechanical  devices  available  for  the  simul- 
taneous lighting  and  extinguishing  of  public 
street  lamps,  some  driven  by  clockwork,  others 
by  pneumatic  pressure  of  the  gas  itself. 

DOMESTIC  AND  TRADE  USES. — About  50  % 
of  the  gas  sold  in  towns  is  consumed  for 
domestic  fuel  purposes,  chiefly  cooking  and 
warming  of  rooms.  It  is  also  fast  coming  into 
use  for  heating  water  circulators  in  substitu- 
tion for  kitchener  boilers.  Discounts  up  to 
25  °/0  on  the  normal  price,  according  to 
quantity,  are  usually  allowed  for  gas  consumed 
as  fuel  for  trade  and  industrial  purposes,  and 
for  gas  engines.  It  is  claimed  that  the 
cheapest  electric  light  for  large  business  pre- 
mises is  provided  by  means  of  private  gas 
power.  The  consumption  of  town  gas  to 
generate  a  unit  of  electricity  on  the  pre- 
mises is  about  30  cu.  ft.  High  temperature 
furnaces  for  glass  melting,  enamelling,  or 
steel  brazing  and  tempering  are  economically 
worked  with  high  pressure  gas. 

WATER  GAS  (CARBURETTED)  is  largely  manu- 
factured in  British  towns,  especially  where 
the  gas  coal  supply  is  railway  borne,  to  sup- 
plement the  bulk  coal-gas  output.  Its  com- 
parative cost  to  the  latter  in  the  holder  differs 
in  different  localities,  and  therefore  it  is  not 
everywhere  equally  favoured.  This  also  largely 
depends  upon  the  current  price  of  the  oil  used 
in  the.  manufacture.  Apart  from  the  bare  fact 
of  the  works  cost  of  this  kind  of  gas,  its  in- 
cidental and  consequential  recommendations 
are  considerable.  It  can  be  installed  at  a  very 


190 


GAS 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


GAS 


important  saving  of  capital,  which  is  a  great 
advantage  where  increased  producing  power  is 
required  for  a  heavily-capitalised  undertaking. 
It  can  be  held  as  a  stand-by  with  far  less  cost 
and  trouble  than  reserve  coal-gas  plant.     It  is 
a  check  upon  labour  difficulties.     When  coke 
is  a  drug  in  the  market  it  provides  a  profitable 
outlet  for  the  surplus  of  this  residual,  and  this 
feature   alone   in   many   places   justifies   the 
manufacture.     Carburetted  water   gas  is  not 
often  sent  out  in  this  country  in  a  larger  pro- 
portion   than  50  °/0   of    the   total,    and    less 
than  this  is  the  general  practice.     It  is  pro- 
duced by  first  raising  a  bed  of  incandescent 
coke  in  a  cupola  to  a  high  temperature  by  a 
blast  of  air,  which  is  called  "the  blow,"  and 
then  passing  steam   into    the   glowing  mass 
until  its  temperature  is  again  lowered,  which 
is  called  "  the  run,"  and  so  on  alternately. 
The  "  water  gas  "  resulting  from  the  action  of 
the  coke  upon  the  steam  is  called  "  blue  water 
gas,"  and  in  some    systems    this   product   is 
added  directly  to  the  coal  gas  before  purifica- 
tion.    From  10  to  15  °/0   of   "  blue "   water 
gas,  which  is  non-luminous,  but  has  a  high 
flame  temperature,  can  be  added  to  common 
coal  gas  without  detriment  to  the  incandescent 
lighting  or  the  fuel  value  of  the  latter.     If 
more  water  gas   is   required   to   be  admixed 
with  the  coal  gas  for  town  distribution  it  is 
necessary  to  "  carburet  "  it — that  is,  impart 
to  it  luminosity  and  calorific  power — by  an 
addition   of   petroleum   oil   gas   or   of    some 
hydrocarbon  spirit  vapour.     In  the  process  of 
carburetted  water  gas  manufacture  the  oil  is 
injected  into  the  cupola  system  and  gasified  in 
the  current  of  hot  water  gas.     Where  "  blue  " 
water  gas  is  added  to  the  coal  gas,  the  mixture 
can  be  carburetted  afterwards  by  passing  it 
over  or  through  a  vessel  containing  benzol  or 
petroleum   spirit.     Blue   water   gas   costs   to 
manufacture  about  one-third  the  cost  of  coal 
gas ;   the  carburetting  brings  it  up  to  about 
the  same  works  cost  as  coal  gas  of  the  same 
illuminating  power.  W.  H.  Y.  W. 


Gas  Burners. — Modern  gas  lighting  is  prac- 
tically confined  to  the  various  patterns  and 


sizes  of  incandescent  mantle  burners,  of  which 
the  original,  and  still  the  largest  in  use,  is  the 
Welsbach  Incandescent  Gas  Light  Company's 
"C"  type  of  burner  (Fig.  1).  Since  the 
expiration  of  the  master  patent,  the  British 
market  has  been  flooded  with  cheap  and 
flimsy  makes  of  this  burner,  but  the  genuine 
are  marked  "aur".  These  burners  take  to 
pieces  easily  for  cleaning,  which  is  a  great 
advantage,  as  atmospheric  dust  is  the  chief 
source  of  trouble  with  all  mantle  burners. 
They  have  no  provision  for  regulating  the  gas 
or  air  supply  according  to  the  pressure  of  the 
gas,  and  therefore  are  only  satisfactory  when 
the  gas  inlet  nipple  is  suited  to  the  quality  of 
the  gas  supply  (because  a  burner  made  for 
14-candle  gas  will  not  properly  burn  20-candle 
gas),  and  also  where  the  pressure  is  maintained 
between  thirteen-tenths  and  twenty-tenths. 
Where  higher  pressures  prevail,  and  also  where 
a  varying  proportion  of  carburetted  water  gas 
may  be  supplied,  some  form  of  gas  regulator 
(as  the  "  Pond  "  or  the  "  Nico  ")  is  desirable, 
and  the  fixed  primary  air  holes  should  be  con- 
trolled by  a  thin  brass  adjustable  shutter. 

These  "C"  size  burners  are  the  standard 
for  all  makes  of  mantles.  They  consume  from 
3J  to  4  cu.  ft.  of  gas  per  hour,  according 
to  the  pressure,  and  yield  a  light  intensity 
equal  in  the  horizontal  direction  to  that  of 
60  to  75  candles.  As  the  distribution' of  their 
light  is  mostly  horizontal,  or  upwards,  these 
burners  require  top  reflectors  for  downward 
lighting.  A  valuable  improved  pattern  of 
upright  burner  of  the  type  is  the  "  Bray " 
(Fig.  2)  which  has  several  good  features, 
including  gas  and  air  adjustment.  It  is  well 
suited  for  church  or  theatre  lighting,  as  it 
bears  turning  down  without  lighting  back. 
Messrs.  W.  Sugg  &  Co.  also  make  a  variety  of 
upright  burners,  in  a  series  of  sizes,  for  public 
street  lamps.  The  most  efficient  form  of 
upright  incandescent  burner  is  the  "  Kern  " 
(Fig.  3)  which  yields  20  %  more  light  than 
the  "C"  burner  from  the  same  quantity  of 
gas,  but  is  rather  more  severe  upon  mantles. 
It  does  not  require  a  chimney.  No.  4  "Kerns," 
giving  100  candle-power,  are  much  used  for 


191 


GAS 


ENCYCLOPEDIA  OF 


GAS 


FIG.  1. 


FIG.  3. 


FIG.  4. 


FIG  5. 


FIG.  6. 


192 


GAS 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


GAS 


public  street  lamps.  They  should  be  governed 
down  to  twenty-tenths  pressure,  for  which  pur- 
pose Carpenter's  (South  Metropolitan)  governor 
is  the  best.  An  excellent  pattern  of  storm-proof 
lantern,  with  antivibrator  fitting,  is  shown  in 
Fig.  4.  This  is  suitable  for  all  public  street 
lighting  on  the  ordinary  scale,  for  everything 
short  of  very  wide,  first-class  thoroughfares. 

INVERTED  BURNERS. — Lately  incandescent 
burners  of  the  inverted,  or  semi-inverted  type 
have  seriously  challenged  the  superiority  of 
upright  burners,  being  of  at  least  equal  effi- 
ciency as  illuminants  for  the  quantity  of  gas 
consumed,  and  having  a  better  form  of  light 
distribution.  Fig.  5  shows  a  strong  pattern  of 
inverted  lamp,  the  "  Bland,"  with  protected 
glass  and  top  reflector  for  workshop  use. 
Fig.  6  is  a  "  Nico  Intense  "  lamp  of  the  New 
Inverted  Gas  Lamp  Company,  which  yields  a 
light  of  65  to  70  candle-power  for  an  hourly 
consumption  of  2^  to  2|  cu.  ft.  of  gas.  In 
it  the  supply  of  air  to  the  flame  is  heated,  and 
the  outer  globe  has  no  bottom  orifice.  Fig.  7 
is  a  "  Vesta  Veritas  "  burner,  of  Messrs.  Falk, 
Stadelmann  &  Co.,  based  upon  the  same  prin- 
ciple and  yielding  similar  results.  The  inner 
glass  is  plainly  shown.  A  useful  form  of 
inverted  burner  is  shown  in  Fig.  8,  which  re- 
presents the  adjustable  lamp  of  Messrs.  G. 
Bray  &  Co.  This  can  either  be  fixed  upon  an 
ordinary  gas  bracket,  or  pendant  arm,  in  which 
case  the  gas  and  air  inlets  are  upright,  and 
the  burner  tube  only  is  bent  over  into  the  in- 
verted position,  or,  as  shown  by  the  dotted 
lines,  it  can  be  used  quite  inverted.  This 
fitting  is  very  convenient  for  shops,  and  gives 
little  trouble  in  adjustment. 

The  inverted  form  of  burner  is  also  adapted 
in  several  patterns  to  outdoor  and  public  street 
lamps.  A  windproof  lantern  arrangement  of 
Messrs.  Falk,  Stadelmann  &  Co.  for  a  single 
mantle  is  shown  in  Fig.  9,  and  a  "  Vesta 
Veritas  "  grouped  burner  lamp  is  shown  in 
Fig.  10.  These  lamps  are  much  favoured 
for  outside  shop  lighting,  as  the  light 
is  very  bright,  quite  steady,  and  directed 
wholly  downwards  without  any  shadow.  A 
serviceable  lamp  of  the  same  type,  made 


by   the    Welsbach    Company,    is    shown    in 
Fig.  11. 

HIGH  PRESSURE  GAS  BURNERS. — When  a 
more  brilliant  source  of  light  is  desired  than 
the  ordinary  incandescent  mantle  can  afford, 
the  effect  is  producible  by  artificial  intensi- 
fication of  the  combustion,  which  means  burn- 
ing more  gas  in  less  space,  thus  raising  the 
mantle  temperature.  The  simplest  way  of 
doing  this  is  by  increasing  the  chimney 
draught  of,  say,  a  large  "  Welsbach  Kern " 
burner  (Fig.  12).  The  convenience  of  these 
"  self-intensified  "  lamps  is  that  they  are  quite 
independent  and  self-sufficing.  The  illustra- 
tion is  of  a  300-candle-power  burner  for  indoor 
use,  as  in  the  lighting  of  a  warehouse,  covered 
goods  yard,  &c.  For  outdoor  use  a  Scott- 
Snell  lantern  produces  the  same  effect  by 
mechanical  action  maintained  by  the  heat  of 
combustion. 

The  most  trustworthy  means  of  heightening 
the  brilliancy  of  incandescent  gas  light  is 
pressure-increasing  mechanism  of  a  positive 
kind  which  is  applicable  to  both  indoor  and 
outdoor  lighting,  public  or  private.  There  are 
systems  in  which  the  air,  or  the  air  and  gas 
supply,  are  put  under  higher  pressures  than 
the  normal,  but  in  general  only  the  gas  is  so 
treated.  The  simplest  apparatus  of  the  kind, 
and  highly  efficient,  is  the  water-power  system 
of  Messrs.  James  Keith,  Blackman  &  Co. 
(Fig.  13).  The  compressor,  which  occupies 
little  room,  can  be  set  up  wherever  there  is  a 
water  supply  under  pressure,  and  it  produces 
a  brilliant  mantle  action  under  a  gas  pressure 
of  9  in.  of  water.  A  useful  series  of  upright 
and  inverted  burners  is  available  for  this  treat- 
ment, which  costs  no  more  than  Id.  per 
1,000  cu.  ft.  of  gas  passed  through  the 
apparatus,  while  the  intensity  of  the  light  is 
increased  to  30  candles  per  cubic  foot  con- 
sumed per  hour.  Another  system  achieving 
the  same  objects  is  that  of  Messrs.  Sugg&  Co., 
who  employ  hot  air  or  gas  engine  power  for  the 
purpose,  and  raise  the  gas  pressure  to  about 
17  in.  of  water.  Triple  mantle  lanterns  so 
illuminated  constitute  lighting  units  of  1,000 
candle-power.  Another  system,  the  Sale- 


M.S.E. 


193 


GAS 


ENCYCLOPEDIA  OF 


GAS 


FIG.  7. 


FIG.  10. 


FIG.  11. 


FIG.  9. 


FIG.  15. 


194 


GAS 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


GAS 


Onslow,  supplies  upright  mantles  with  gas  at 
54  in.  pressure. 

The  most  brilliant  gas  light  of  the  period  is 
that   produced   by   the    inverted    system    of 


FIG.  13. 

Messrs.  James  Keith,  Blackman  &  Co., 
worked  at  a  gas  pressure  of  54  in.  of  water 
(4  in.  of  mercury).  The  compressor  is 
driven  by  electric  power  (Fig.  14).  The  effi- 
ciency of  the  mantles  is  about  60  candle-power 
per  cubic  foot  of  gas  consumed  in  the  lanterns 
such  as  are  shown  in  Fig.  15.  The  whole 
equipment  is  substantially  constructed,  and 
the  lanterns  are  durable.  A  peculiarity  of  this 
system  is  that  the  mantles  are  put  on  in  the 


FIG.  14. 

soft  condition,  and  shape  themselves  as  the 
flame  is  turned  on.  Various  sizes  of  lamps 
can  be  used  on  the  same  supply.  The  light  is 
suitable  for  large  factories,  railway  yards, 
wharves,  and  the  most  important  main  city 
thoroughfares.  W.  H.  Y.  W. 

Gas  and  Electric  Light  Testing.— The 

testing  of  gas  is  generally  confined  for  practical 
purposes  to  the  estimation  of  the  illuminative 


value  when  burnt  under  defined  conditions ; 
to  the  determination  of  its  heating  power  and 
the  pressure  of  the  gas  in  the  service.  For- 
merly the  quantity  of  sulphur  present  in  the 
gas  either  in  the  form  of  sulphuretted  hydrogen 
and  other  sulphur  compounds  was  considered 
of  importance,  but  recent  legislation  has 
omitted  for  all  practical  purposes  any  restric- 
tion on  these  in  the  metropolis,  and  for  many 
years  past  they  have  rarely  been  considered 
in  connection  with  the  supply  to  the  provinces. 

In  the  case  of  the  electric  light  the  essential 
features  of  the  test  are  the  intensity  of  light 
yielded  and  the  current  required,  expressed  in 
terms  of  volts  and  amperes  or  "  Board  of 
Trade  units." 

The  measurement  of  the  light  in  both  cases 
involves  the  same  photometrical  procedure, 
and  is  based  upon  the  natural  law  that  the 
intensity  of  the  light  emitted  by  a  given  radiant 
diminishes  in  inverse  ratio  to  the  square  of 
the  distance.  The  following  example  will 
illustrate  this  :— 

When  it  is  desired  to  compare  a  light 
with  a  standard  light,  a  candle  for  instance, 
if  a  translucent  paper  having  a  spot  of 
grease  in  the  centre  is  held  between  the 
two  lights  it  is  clear  that  if  it  is  too  close 
to  one  radiant  the  light  will  be  too  bright  on 
the  side  of  the  paper  nearest  to  it,  and  the 
light  will  shine  brightly  through  the  greased 
portion.  If  the  paper  is  then  carried  over  to 
the  opposed  radiant  the  effect  will  be  trans- 
posed, but  in  its  passage  from  one  to  the 
other  it  will  be  seen  that  at  some  point 
between  them  the  illumination  of  each  side 
of  the  paper  will  be  equal  and  the  grease  spot 
will  all  but  entirely  disappear  in  consequence 
of  the  reflected  and  transmitted  light  being 
equal  on  either  side.  This  neutral  point  hav- 
ing been  found,  it  is  clear  that  the  actual 
intensities  are  equal  at  the  given  distance  from 
the  respective  lights.  Simple  calculation  then 
gives  the  relative  intensities  thus :  If  the 
distance  of  the  one  light  be  26  in.  from 

the    neutral    point   and    that   of    the   other 

442 
44  in.,  then  ^^  =  2'86,  so  that  the  greater  light 


195 


o2 


GAS 


ENCYCLOPEDIA   OF 


GAS 


of  the  two  is  2'86  times  that  of  the  weaker. 
If  the  latter  be  known  to  be,  say,  equal  to 
8  candles,  i.e.,  a  low-power  incandescent 
electric  light,  the  actual  intensity  of  the  greater 
will  be  2-86  X  8  =  22*88  candles.  In  England 
the  standards  of  comparison  generally  em- 
ployed are  either  the  Parliamentary  standard 
sperm  candle,  consuming  spermaceti  at  the 
rate  of  126  grains  per  hour,  the  sperm  con- 
sumption being  ascertained  by  weight  and 
the  intensity  of  the  light,  presumed  to  vary 
with  the  rate  of  consumption,  which  must  not 
exceed  126  grains  per  hour  nor  fall  below  114. 
In  the  metropolis  the  standard  employed  at 
the  gas-testing  stations  is  that  known  as 
Harcourt's  10-candle  pentane  lamp,  which 
consumes  the  vapour  of  pentane  (obtained 
from  light  petroleum  spirit)  carried  forward  to 
the  burner  by  a  current  of  air.  When  the 
flame  is  at  the  regulated  height  the  intensity 
is  taken  to  be  equal  to  10  standard  candles, 
and  no  further  calculation  is  needed  in  that 
respect.  Many  alternative  standards  have 
been  proposed,  but  beyond  certain  calibrated 
electric  incandescent  lamps  used  for  temporary 
purposes  either  of  the  foregoing  are  generally 
employed. 

The  instruments  known  as  photometers  are 
of  many  divergent  patterns,  but  the  essentials 
comprise  simply  supports  for  the  two  lumin- 
ous radiants  to  be  compared  and  the  com- 
parison screen  which  may  be  either  Bunsen's 
greased  disc  above  described,  or  its  alternative, 
the  star  disc  of  Leeson,  consisting  of  a  thick 
piece  of  paper  with  a  perforation  in  the  shape 
of  a  star,  covered  on  either  side  with  a  thin 
paper,  thus  giving  opaque  surfaces  with  a 
translucent  centre.  This  is  best  for  comparing 
coloured  lights  of  different  character.  The 
principle  of  Eumford's  shadow  photometer — in 
which  the  comparison  is  made  by  noting  the 
depth  of  shadow  cast  by  two  vertical  rods 
illuminated  by  the  respective  lights,  which  are 
moved  nearer  to  or  further  from  the  rods  until 
the  shadows  are  of  equal  depth,  or,  more 
truly  speaking,  the  illuminated  surfaces  are 
of  equal  brightness — is  employed  in  the  table 
photometer  used  in  the  official  testings.  The 


accessory  apparatus  necessary  for  testing  the 
illuminating  power  of  coal  gas  consists  in  a 
meter  for  measuring  the  rate  of  consumption, 
which  is  generally  5  cu.  ft.  per  hour,  a  clock 
with  stop  action  to  denote  time  intervals, 
a  governor  to  control  the  steady  flow  of  gas 
to  the  testing  burner,  and  a  pressure  gauge  to 
test  the  pressures  in  the  different  parts  of  the 
apparatus.  The  most  complete  "  bar  "  photo- 
meter comprising  the  whole  of  these  neces- 
saries is  that  known  as  the  "  Tooley- Street 
pattern,"  which  gives  the  steadiest  flame  to 
the  gas  and  candles  by  reason  of  the  freedom 
from  side  and  top  draughts.  This  was  developed 
as  the  results  of  experiments  by  the  writer  at 
the  time  when  the  late  Professor  Tyndal  was 
one  of  the  Gas  Keferees,  the  principle  involved 
being  the  attainment  of  a  large  volume  of  air 
moving  at  a  slow  intensity  in  a  steady  upward 
direction,  with  the  result  that  an  ample  supply 
of  air  was  carried  to  the  burners  and  the 
products  of  combustion  freely  and  steadily 
removed  without  top  or  side  draughts. 

The  candles  are  carried  during  the  test  in 
a  suitable  balance,  and  the  quantity  of  sperm 
consumed  weighed  with  the  candles  in  situ,  as 
great  risk  is  incurred  if  they  are  touched,  by 
reason  of  spilling  some  of  the  melted  sperm, 
or  otherwise  disarranging  the  rate  of  con- 
sumption. If  required,  any  other  standard  of 
comparison  may  be  employed  in  this  photo- 
meter, and  in  the  case  of  testing  powerful  gas 
or  electric  lights  these  may  be  placed  on  suit- 
able supports  in  a  line  with  the  photometer 
bar,  the  side  of  the  casing  surrounding  the 
gas  burner  being  removed,  and  the  usual  scale 
on  the  bar  being  neglected,  the  respective 
distances  being  measured  as  above  indicated  ; 
or  a  special  scale  may  be  engraved  on  the 
bar,  the  usual  one  being  for  lights  60  in. 
apart,  the  readings  in  that  case  being  made 
direct  instead  of  having  to  be  calculated  as 
made.  It  is  unnecessary  here  to  enter  into 
details  of  the  method  of  computing  the  rate  of 
consumption  of  the  gas  and  candles,  as  tables 
are  generally  provided  with  the  instruments. 
An  important  branch  of  this  work  is  that 
introduced  by  the  writer  in  1885  under  the 


196 


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MUNICIPAL   AND    SANITAEY  ENGINEERING. 


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term,  "  Eadial  Photometry,"  which  denoted 
the  estimation  of  rays  in  all  directions  emitted 
from  a  light  source.  According  to  the  then 
usual  practice  only  the  horizontal  rays  were 
taken  account  of,  but  the  introduction  of  the 
inverted  and  other  burners  rendered  it  neces- 
sary to  estimate  in  particular  those  rays  falling 
at  varying  angles  from  the  horizontal  to  the 
perpendicular.  For  this  purpose  the  radial 
photometer  was  made  by  Messrs.  Sugg  &  Co. 
to  the  writer's  design. 

The  support  for  the  illuminant  is  attached 
to  and  shown  in  front  of  the  raised  disc,  which 
slides  up  and  down  in  its  stand.  The  disc  of 
paper,  greased  or  stained  as  required,  is  held 
in  the  clamp  in  front  of  the  lower  disc  on  the 
right-hand  support.  Fixed  rigidly  to  the  sup- 
porting block  is  the  horizontal  bar  on  which 
slides  the  comparison  standard  light.  As  the 
inclined  bar  is  moved  by  any  alteration  in 
the  position  of  either  block,  the  taller  of  the 
two  upright  supports  slides  sideways  on  the 
base  board,  thus  always  maintaining  the  full 
distance  of  the  light  from  the  disc — the 
arrangements  being  such  that  the  light  may 
either  be  directly  above  the  disc  or  below  it — 
the  moving  bar  indicating  and  controlling  the 
direction  of  the  rays.  Many  alternative 
methods  have  been  proposed,  but  this  is  the 
most  complete  instrument  for  the  work  and  is 
extremely  easy  to  manipulate,  even  with 
lanterns  of  many  hundred  candle  -  power 
intensity. 

A  convenient  portable  instrument  was  de- 
signed by  Mr.  Trotter,  and  described  by  him 
in  a  paper  read  before  the  Institute  of  Civil 
Engineers  in  1892.  It  was  designed  for 
estimating  the  intensity  of  street  lighting. 

A  small  standardised  electric  lamp  was  fitted 
at  one  end  of  a  box.  The  light  from  this  was 
received  on  a  reflecting  screen  of  Bristol  board 
mounted  on  an  axis  through  its  upper  edge. 
Above  this  a  simple  cardboard  screen  with  a 
star-shaped  hole  cut  in  it  was  fixed  in  a  hori- 
zontal position,  so  that  the  observer  when 
looking  down  on  the  box  would  see  the  reflect- 
ing screen  through  the  star-shaped  opening. 
The  method  of  observation  consisted  in 


inclining  the  reflecting  screen  at  different 
angles,  this  motion  being  given  by  a  fine  chain 
wound  on  a  snail  cam.  A  convex  lens  was 
used  in  certain  cases  to  increase  the  available 
light  from  the  electric  lamp. 

The  results  of  the  tests  of  illuminative  value 
are  controlled  by  the  quantity  of  gas  con- 
sumed in  the  case  of  that  illuminant,  or  the 
strength  of  the  current  in  the  case  of  electricity. 
In  the  case  of  gas  it  is  not  the  pressure  which 
is  the  governing  factor,  but  the  chemical  or 
illuminating  constituents,  or  even  more  im- 
portant in  certain  respects,  the  heating  quality, 
and  hence  it  is  that  tests  for  the  calorific  value 
of  the  gas  seem  likely  to  displace  to  a  great 
extent  those  for  mere  illuminating  value.  In 
the  case  of  electricity  the  equivalent  factor  is 
the  voltage,  a  given  volume  or  amperes  being 
assumed,  and  the  tolerance  shown  by  public 
authorities  to  the  electrical  industry  by  neglect 
to  establish  a  severe  system  of  tests  and 
punishments  for  default  in  supply,  as  in  the 
case  of  gas,  has  gone  not  a  little  way  to 
encourage  the  growth  of  the  newcomer  in  the 
field  of  luminous  energy.  For  instance,  a  few 
percentages  different  in  the  photometrical 
value  of  gas  makes  but  little  difference,  but 
may  be  punished  with  heavy  and  irritating 
penalties.  On  the  other  hand,  what  happens 
if  the  voltage  of  a  supply  drops  ?  From  tests 
made  by  the  writer  it  was  found  that  a  16- 
candle-power  lamp  was  found  to  give  15*03 
when  the  current  indicated  99'33  volts ;  but 
at  96  volts  the  luminous  intensity  fell  to  10'9 
candles,  or  27*3,  and  when  it  fell  to  90  volts 
the  loss  of  candle-power  was  exactly  50  per 
cent.  It  is  therefore  clear  that  the  necessity 
for  maintained  voltage  is  of  the  greatest 
importance,  and  too  much  stress  cannot  be 
laid  upon  it,  especially  when  it  is  considered 
that  this  difference  in  voltage  makes  practically 
little  on  the  quarterly  account  which  is  based 
on  the  Board  of  Trade  unit,  i.e.  quantity  = 
amperes,  multiplied  by  intensity  =  volts.  Thus 
1,000  amperes  x  1  volt  =  1,000  =  1  B.T.U., 
or  10  amperes  X  100  volts  =  1  B.T.U.,  which 
latter  might  represent  the  above  case,  when  a 
drop  of  10  volts  out  of  100  would  mean,  with 


197 


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ENCYCLOPAEDIA   OF 


GAS 


the  sample  amperes,  900,  or  a  reduction  of     in  the  steam-engine.     In  the  internal-combus- 


10  %  on  the  bill  for  a  50%  reduction  of 
light. 

It  is  impossible  within  the  compass  of  the 
present  article  to  discuss  the  questions  of 
Calorimetry  ;  Illuminating  Effect,  i.e.,  suitable 
distance  of  a  light  from  a  surface  to  be  illu- 
minated ;  Illuminating  Value,  i.e.,  intensity  of 
the  light  which  would  be  required  at  a  foot 
distance  to  produce  the  effect  of  the  given 
light  at  its  given  distance,  and  other  similar 
points.  These  should  be  studied  in  the  text- 
books devoted  to  Public  Lighting,  &c. 

The  following  comparison  of  cost  of  illumina- 
tion by  various  methods  will  be  of  interest. 
It  is  abstracted  from  the  writer's  work  on 
"  Public  Lighting." 

Electricity  at  4d.  per  B.T.U. 

Coal  gas  at  3s.  per  1,000  cu.  ft. 


Cost  of 

producing 
1,000 

Cost 

Candles  of 

of  each 

Light 
during 

Light 
per  hour. 

one  hour. 

Electricity  : 

Pence. 

Pence. 

Arc  Lamp 

450  c.p. 

2-2 

1-0 

,,          Frosted  Globe 

4-0 

1-0 

Opal           ,, 

6-7 

1-0 

Incandescent  Lamp  .  . 

16-0     , 

12-5 

0-2 

Nernst  Lamp 

65-0     , 

6-2 

0-4 

Coal  Gas  : 

Flat  Flame  Burners  .  . 

13-0     , 

13-8 

0-18 

Argand               ,, 

16-0     , 

11-2 

0-18 

Welsbach  Mantle 

60-0     , 

2-1 

0-13 

Intensified       ,, 

300-0     , 

1-2 

0-36 

Petroleum  : 

Kitson's  Incandescent 

1000-0     , 

0-8 

0-80 

Flat  Flame      .  . 

9-5     , 

9-5 

0-09 

W.  J.  D. 

Gas  Engines. — Heat  engines  are  classified 
either  as  internal  or  external-combustion 
engines.  In  the  external-combustion  engine, 
heat  is  generated  in  a  furnace  and  transmitted 
through  the  metal  sides  of  a  vessel  containing 
a  working  fluid,  as  in  the  case  of  the  ordinary 
steam  boiler.  The  water  so  contained  forms 
the  medium  by  which  part  of  the  heat  given 
out  by  the  fuel  is  transformed  into  another 
form  of  energy  and  thence  passed  on  for  use 


tion  engine  the  heat-producing  materials  are, 
at  the  outset,  introduced  into  the  working 
cylinder  uncombined,  and  there  develop  the 
whole  of  the  heat  due  to  combustion,  and 
finally,  after  having  done  work  in  the 
cylinder,  are  ejected  from  it  as  waste  products 
of  combustion.  The  internal-combustion 
engine,  in  thus  having  the  whole  heat  gene- 
rated within  the  cylinder,  possesses  an  impor- 
tant advantage  from  a  thermo-dynamic  point 
of  view,  seeing  that,  in  external-combustion 
engines,  from  25  to  30  %  or  more  of  the  total 
heat  produced  is  lost  in  the  flue  gases  by 
radiation  and  other  causes.  It  has  to  be 
borne  in  mind,  however,  that  the  temperature 
of  the  cylinder  of  an  internal-combustion 
engine,  of  which  gas  and  oil-engines  are 
the  best  examples,  must,  for  practical  reasons, 
be  constantly  kept  below  a  certain  limit  by 
cooling  by  means  of  a  water-jacket,  and  this 
operation  involves  a  waste  even  in  excess  of 
the  chimney  waste  above-named.  Notwith- 
standing the  fact  that  some  50  %  of  the  total 
heat  generated  in  the  gas-engine  cylinder  is 
lost  by  the  water-jacket  in  this  way,  experience 
shows  that  a  higher  thermo-dynamic  efficiency 
can  be  realised  in  practice  in  internal-combus- 
tion engines  than  has  yet  been  obtainable  in 
even  the  best  examples  of  the  external-com- 
bustion type.  With  the  view  of  testing  the 
comparative  efficiency  of  large  gas-engines 
worked  with  Dowson  gas  and  of  a  good  steam- 
engine  and  boiler,  Professor  Witz,  of  Lille, 
carried  out  experiments  which  yielded  the 
following  thermo-dynamic  efficiencies1  :— 

Per  cent. 

Steam  boiler 68  to  76 

Gas-producer  ...         ...         ...         70*6 

Steam-engine  ...         ...         ...  9'7 

Gas-engine       ...         ...         ...         18'0 

Steam-engine  and  boiler        ...  7*0 

Gas-engine  and  producer       . . .         12'7 

Dowson  gas,  obtained  from  a  producer 
worked  with  anthracite  and  coke  was  used 
with  a  112  I.H.P.  single  cylinder  gas-engine, 


1  "  Proc.  Inst.  C.  E.,"  vol.  cix. 


198 


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MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


GAS 


and  the  total  consumption  of  fuel  was  T349  Ib. 
per  brake  horse-power  per  hour.  The  steam- 
engine  under  trial  was  a  simple  jacketed  con- 
densing-engine,  with  steam  at  75  Ibs.  per  square 
inch  generated  in  a  boiler  with  economiser,  and 
a  coal  consumption  of  2'4  to  2'7  Ibs.  per  brake 
horse-power  hour.  Even  when  a  gas-producer 
is  used,  the  internal-combustion  engine  shows 
a  considerable  efficiency  over  the  steam-engine, 
and  where,  as  in  the  case  of  an  oil-engine,  the 
fuel  is  introduced  directly  into  the  cylinder 
without  any  external  losses,  the  thermo- 
dynamic  efficiency  of  the  internal-combustion 
engine  will  show  a  still  more  favourable  com- 
parison with  the  steam-engine  and  boiler.  In 
large  sized  steam-engines  higher  efficiencies 
than  that  assumed  above  are  readily  obtain- 
able, but,  at  the  same  time,  the  internal- 
combustion  engine,  comparatively  speaking, 
is  in  its  early  stages,  and  further  important 
improvements  may  be  confidently  anticipated. 
The  commercial  history  of  the  gas-engine 
dates  from  1876,  when  Dr.  Otto  introduced 
the  well-known  Otto-Crossley  engine  now  so 
widely  used,  and  applied  the  cycle  of  operations 
originally  suggested  by  Beau  de  Eochas  in 
1862.  Since  1876,  the  development  of  the 
gas-engine  has  been  more  in  the  improvement 
of  details  of  construction,  increased  efficiency, 
and  the  use  of  higher  compressions,  than  in 
the  introduction  of  any  entirely  new  type  of 
engine.  The  original  Otto  gas-engine  is  a 
thing  of  the  past,  but  the  present  general 
uniformity  in  design  of  gas-engines  is  a 
strong  indication  that  the  "  Otto  cycle "  is 
best  suited  to  the  commercial  gas-engine, 
although  there  may  be  considerable  variety 
in  other  details. 

The  Otto  cycle  engines  are  explosion 
engines  in  which  the  combustible  gaseous 
mixture  is  compressed  previous  to  the 
explosion.  The  "  cycle "  consists  of  five 
operations,  viz.  : — 

(Outstroke,  charges  the  cylinder  with  gas 
First  and  air  mixture  at  atmospheric  pressure, 

revolution  1 Instroke,  compresses  the   charge   into   a 
I      combustion  space. 

Dead  centre,  the  charge  explodes. 


(Outstroke  (caused  by  the  explosion),  ex- 
Second    I      pansion  of  the  gases, 
revolution  j  Instroke  (due  to  action  of  fly-wheel),  expul- 
I      sion  of  the  burnt  gases  from  the  cylinder. 

An  impulse  to  the  piston  is  thus  only  given 
every  two  revolutions  (i.e.  four  strokes)  of  the 
engine,  so  that  a  very  heavy  fly-wheel  is 
necessary  to  maintain  a  constant  speed. 

In  the  Otto-Crossley  engine,  the  cylinder, 
which  acts  alternately  as  a  motor  and  a  pump, 
is  open-ended  and  horizontal,  and  in  it  works 
a  long  trunk  piston,  the  front  of  which  carries 
the  cross-head  pin.  The  cylinder  is  much 
longer  than  the  stroke  and  the  piston  thus 
leaves  a  space,  known  as  the  "  combustion 
space,"  in  which  the  charge  is  first  compressed 
on  the  inward  stroke  as  above-named  and  then 
burned.  In  a  gas  or  oil-engine  a  large  amount 
of  stored  energy  is  needed  to  carry  the  piston 
through  the  negative  portion  of  the  cycle  as 
set  out  above,  and  for  that  purpose  a  large 
fly-wheel  and  heavy  crank  shaft  are  provided. 
The  valves  are  four  in  number — the  charge 
inlet  valve,  gas  inlet  valve,  igniting  valve,  and 
exhaust  valve — and  are  all  of  the  conical 
seated  lift  type.  The  igniting  or  timing  valve 
determines  the  time  of  the  explosion.  One  of 
the  latest  improvements  in  the  Crossley 
engines  is  due  to  the  introduction  of  a 
"  scavenging  "  arrangement  by  which  the 
exhaust  gases  remaining  in  the  clearance 
space  are  drawn  away  at  the  end  of  the  stroke. 

Self-starters  have  become  necessary  with  the 
introduction  of  large-sized  gas  engines,  as  the 
starting  of  these  would  present  considerable 
difficulty  by  simply  pulling  the  fly-wheels 
round  as  in  the  smaller  engines.  Various 
methods  are  employed  by  different  makers, 
but  the  general  idea  is  to  store  up  a  small 
amount  of  energy  in  a  separate  vessel  for  the 
purpose  of  giving,  when  re-starting,  the  first 
impulse  to  the  piston.  In  the  Westinghouse 
double-acting  engines  of  large  size  an  auto- 
matic compressed  air  starter  is  supplied, 
in  which  air  is  stored  during  the  previous 
run,  or  is  separately  compressed  and  is  turned 
into  one  cylinder  of  the  engine — the  valve 
functions  of  which  have  been  altered — until 


199 


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explosion  takes  place  in  the  others,  when  the 
air  is  cut  off  from  the  starting  cylinder,  which 
then  resumes  its  normal  functions.  Some 
makers  adopt  the  method  of  filling  the  cylin- 
der with  gas  and  then  open  a  connection  to  a 
compressed  air  vessel  from  which  sufficient 
air  under  pressure  is  allowed  to  flow  until  a 
rich  explosive  mixture  is  formed  at  a  consider- 
able pressure,  which,  upon  ignition,  gives  an 
effective  starting  impulse.  An  important 
practical  point  to  be  taken  into  consideration 
when  adopting  large  size  gas-engines  is  the 
avoidance  of  nuisance  caused  by  their  running. 
This  may  arise  from  the  noise  or  smell  of  the 
exhaust  or  from  air  or  ground  vibration. 
The  noise  from  the  exhaust  may  be  deadened 
by  conducting  it  into  a  "  silencing  chamber," 
or  pit  placed  underground  containing  large 
pebbles  or  stones  from  which  an  outlet  pipe 
gives  relief  into  the  open  air.  Internal  air 
vibration  is  often  caused  by  the  displacement 
of  a  large  trunk  piston  setting  up  rapid  pulsa- 
tions of  air  which  may  be  transmitted  through- 
out the  passages  and  other  rooms  of  a  large 
building  if  such  directly  communicate  with 
the  engine-room.  Ground  vibration  is  often 
set  up  by  the  running  of  large  engines,  also 
vibration  not  only  to  the  walls  of  the  building 
in  which  the  machinery  is  situated,  but  also  to 
those  of  adjoining  properties.  Such  vibration 
may  be  transmitted  considerable  distances 
through  the  ground  or  communicated  to  the 
walls  direct  where  the  foundations  of  the 
engine  abut  thereon.  Where  a  material 
nuisance  is  alleged  to  be  caused  in  this  way 
to  neighbouring  properties,  the  prevention  of 
such  vibrations  is  often  a  problem  of  consider- 
able difficulty.  An  alteration  of  the  speed  of 
running  has  in  some  cases  reduced  the  trouble, 
possibly  due  to  the  altered  period  of  vibration. 
If  such  period  happens  to  coincide  with  that 
of  the  building  itself,  the  resulting  vibration 
is  likely  to  become  more  pronounced.  Another 
remedy  applicable  in  some  cases  is  the  bolting 
down  of  the  engine  upon  a  yielding  and 
springy  bed,  such  as  thick  cocoanut  matting 
or  similar  material,  sandwiched  between  two 
iron  plates,  the  whole  being  securely  held 


together  by  strong  foundation  bolts.  In  a 
gas  or  oil-engine  the  water-jacket  surrounding 
the  working  cylinder  is  required  to  perform 
the  important  function  of  conveying  away  the 
excess  of  heat  due  to  combustion  in  the 
cylinder  which  cannot  under  present  con- 
ditions be  converted  into  useful  work.  By 
this  means  the  temperature  of  the  cylinder  is 
kept  within  suitable  limits  without  which 
lubrication  would  be  impossible.  The  heat 
absorbed  by  the  jacket-water  amounts  to 
from  30  to  50  %  of  the  total  generated  by  the 
combustion  of  the  gases  in  the  cylinder.  The 
circulation  of  the  water  takes  place  in  an 
annular  space,  of  from  f  in.  to  2  in.,  cast 
around  the  cylinder,  at  the  underside  of  which 
the  cool  circulating  water  enters  and  from  the 
top  of  which  the  heated  water  flows  away  to 
the  circulating  water  storage  tanks,  or  as  may 
be  arranged.  The  maximum  temperature  of 
the  circulating  water  should  not  exceed  150°F., 
and,  with  water  of  60°  at  the  inlet,  the 
quantity  required  to  keep  the  cylinder  cool 
will  be  from  4^  to  5  gallons  per  I.H.P.  hour. 
The  circulation  is  generally  arranged  through 
circulating  tanks  having  a  capacity  of  from 
20  to  30  gallons  per  I.H.P.  The  jacket  pipes 
will  be  from  1  in.  to  2  in.  diameter  for  engines 
up  to  about  20  I.H.P.,  and  from  2  in.  to  3  in. 
for  inlet  with  2^  in.  to  3J  in.  for  the  outlet  in 
the  case  of  larger  engines.  Sometimes  several 
circulating  tanks  are  arranged  in  series,  the 
pipe  connections  being  arranged  so  that  the 
water  is  drawn  from  the  bottom  of  one  tank 
to  the  top  of  the  next  in  the  order  of  the 
circulation.  In  order  that  the  consumption 
and  working  of  each  engine  may  be  indepen- 
dently checked,  a  separate  gas-meter  should  be 
provided  for  each  ;  it  should  be  placed  outside 
the  engine-room  in  an  atmosphere  of  normal 
temperature  as  an  increase  of  temperature 
means  an  increase  in  the  volume  of  gas  for  the 
same  weight.  A  flexible  gas-bag  or  bags  should 
be  provided  between  the  meter  and  the  engine, 
in  order  to  reduce  the  effect  of  fluctuations  of 
pressure  in  the  mains.  The  ignition  of  the 
explosive  mixture  within  the  cylinder  of  a  gas- 
engine  without  permitting  escape  of  gas  has 


200 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


GAS 


been  a  detail  of  some  difficulty  in  the  design 
of  the  engine.  It  is  accomplished  in  various 
ways.  In  "  flame-ignition"  aportion  of  burning 
gas  is  carried  through  a  small  aperture  in  the 
slide  when  just  closing.  If  the  aperture 
becomes  carbon  coated,  as  often  happens, 
missfires  are  occasioned.  In  "tube-ignition" 
a  cast-iron  tube  is  maintained  at  white  heat 
by  a  Bunsen  burner,  and  when  the  timing- 
valve  opens,  the  charge,  being  partly  com- 
pressed into  an  ignition  chamber  in  communi- 
cation with  the  tube,  then  ignites.  "  Electric 
ignition"  is  accomplished  by  causing  an 
electric  spark  or  shower  of  sparks  to  take 
place  in  the  cylinder  or  in  a  chamber  brought 
into  communication  therewith. 

GAS  FUELS. — The  fuels  most  commonly 
used  in  gas  engines  are  ordinary  town  coal 
gas,  Dowson-Mond,  or  other  cheap  classes  of 
power  or  generator  gas.  In  the  larger  engines, 
notwithstanding  the  improvements  made  in 
economy  of  gas  consumption,  the  price  of 
ordinary  town  gas  supply  is  usually  too  high 
to  permit  of  its  use  to  advantage  except  when 
working  intermittently.  In  these  circum- 
stances, and  where  the  ordinary  gas  is  not 
available,  a  "gas-producer"  plant  may  be  in- 
stalled to  generate  a  non-illuminating  gas  cost- 
ing (including  all  charges,  depreciation,  wages, 
&c.)  from  2Jrf.  to  4d.  per  1,000  cu.  ft.,  accord- 
ing to  the  size  of  the  plant.  These  gases  are 
poor  in  calorific  value  as  compared  with  coal- 
gas,  and  proportionately  greater  volumes  are 
required  to  evolve  the  same  amount  of  heat. 
The  calorific  value  of  1  cu.  ft.  of  coal  gas 
at  atmospheric  pressure  and  32°  F.  is  from 
600  to  650  British  thermal  units,  whilst 
that  of  a  producer-gas  varies  from  145  to  165 
thermal  units  per  cubic  foot.  From  4  to 
5  volumes  of  the  producer-gas  are  there- 
fore required  to  give  out  the  same  amount  of 
heat  as  one  volume  of  coal-gas,  and  the  cost 
per  1,000  cu.  ft.  must  be  multiplied  by  this 
figure  before  comparison  with  coal-gas.  Not- 
withstanding this,  the  producer-gas  shows  a 
large  saving,  which,  with  coal  gas  at  3s.  per 
1,000  cu.  ft.,  may  vary  from  30  to  60  % 
according  to  the  size  of  the  plant. 


The  process  of  manufacture  of  Dowson  gas, 
now  so  extensively  used,  consists  in  injecting 
a  mixture  of  superheated  steam  and  air 
through  incandescent  coke  or  anthracite  and 
collecting  the  resulting  gas.  There  is  no 
external  fire  as  with  ordinary  gas  retorts,  and 
the  production  is  automatically  regulated  from 
the  gas-holder  without  the  employment  of 
skilled  labour  to  work  the  apparatus.  Its 
heating  value  is  equivalent  to  about  150 
British  thermal  units  per  cubic  foot,  and  the 
quantity  of  air  required  for  its  complete  com- 
bustion is  only  from  1  to  1£  volumes  to  1 
volume  of  the  gas.  The  capacity  of  an  engine 
cylinder  is,  therefore,  suitable  for  either  coal 
or  Dowson  gas,  the  gas  and  air  valves  being 
adjusted  to  admit  more  gas  and  less  air.  The 
products  of  combustion  of  Dowson  gas  must 
be  expelled  from  the  cylinder  or  their  presence 
will  cause  the  fresh  charge  to  miss  fire.  This 
is  done  by  what  is  called  the  "  scavenger 
stroke  "  or  its  equivalent.  The  average  fuel 
consumption  for  a  gas-engine  driven  by  Dow- 
son gas  varies  from  about  1  Ib.  per  I.H.P. 
for  the  larger  engines  to  1^  Ib.  per  H.P. 
for  the  smaller  sizes.  In  engines  fed  from 
the  town  gas  supply  the  guaranteed  consump- 
tion is  now  usually  from  15  to  20  cu.  ft.  per 
I.H.P.  per  hour,  according  to  the  size  of  the 
engine  and  quality  of  the  gas. 

TESTING  GAS-ENGINES. — The  testing  of  a 
gas-engine  is,  in  many  respects,  very  similar 
to  a  steam-engine,  but  there  are  important 
distinctions  to  be  kept  in  view.  Indicator 
diagrams  cannot  be  entirely  relied  upon, 
though  if  carefully  taken  they  are  useful  for 
practical  purposes.  The  brake  horse  power  of 
a  gas-engine  should  always  be  taken  as  the 
measure  of  its  duty  in  preference  to  the  indi- 
cated. Yery  stiff  springs  must  be  used  in  the 
indicator  (from  TJ<j  to  ^50)  so  tnat  onlv  tne 
compression,  explosion  and  expansion  curves 
are  clearly  given  by  the  diagram  obtained. 
Besides  the  indicator  diagrams  taken  during 
a  trial,  it  will  be  necessary  to  note  the  brake 
readings  of  the  spring  balance  and  load  on 
brake,  the  speed  of  the  engine  and  number  of 
explosions  per  minute,  also  the  quantity  of 


201 


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GAS 


gas  used  in  cubic  feet  with  its  temperature 
and  pressure,  as  well  as  the  weight  of  the 
jacket- water  and  its  inlet  and  outlet  tempera- 
tures. The  reading  of  the  barometer  and,  if 
possible,  the  temperature  of  the  exhaust  are 
also  noted.  W.  H.  M. 

Gas  Water-Liquor  Purification. — The 

impurities  washed   away   during  the  process 


ammonia  is  valuable  as  a  fertilizer.  It  is 
recovered  by  boiling  this  liquor  (adding  lime 
at  an  intermediate  stage  for  the  decomposition 
of  combined  ammonia)  and  usually  absorbing 
the  evolved  gases  in  sulphuric  acid.  From 
100  tons  of  coal  there  will  be  obtained  one 
ton  of  sulphate  of  ammonia  value  about  £l'2. 
The  costs,  consisting  of  acid,  lime,  coke, 
labour,  bagging,  and  wear  and  tear,  amount 


Ammonia  Waste  Liquor  Purification  Plant  (BadcliflVs  Patents). 


of  purifying  gas  are  principally  ammonia, 
sulphuretted  hydrogen,  carbonic  acid  and 
cyanogen  compounds.  Phenols  and  cresols 
are  also  present  in  this  ammoniacal  liquid 
through  cooling  of  the  hot  gas.  The 


to  £3  15s.  Of/.,  thus  leaving  a  profit  per  100 
tons  of  coal  (equal  to  1,000,000  cubic  feet  of 
gas)  of  £8  5s.  Od.  From  one  ton  of  sulphate  of 
ammonia  there  is  produced  about  2,500  gallons 
of  a  waste  liqour  containing  free  lime, 


202 


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MUNICIPAL   AND    SANITAKY  ENGINEEBING. 


GAU 


hyposulphite,  sulphate,  carbonate,  cyanide 
and  sulpho-cyanide  of  lime,  and  phenols  and 
cresols.  It  is  antiseptic,  and  has  an  oxygen 
absorption  test  of  between  400  and  600.  Its 
common  destination  is  the  sewers.  Since  the 
development  of  the  bacterial  processes  for 
the  purification  of  sewage  many  local  authori- 
ties have  been  obliged  to  exercise  their  powers 
and  prohibit  its  discharge,  because  with  this 
material  present,  the  difficulties  and  expense 
of  the  problem  of  sewage  purification  is  vastly 
increased.  On  the  other  hand  gas  under- 
takings have  to  face  a  considerable  loss  of 
revenue.  While  most  large  gas  undertakings 
work  up  their  liquor  as  above  described, 
smaller  concerns  sell  their  product  as  liquor 
to  a  chemical  works.  In  the  locality  of  these 
chemical  works  the  problem  is  still  further 
increased  in  difficulty.  A  process  has  been 
introduced  by  J.  Kadcliffe,  of  East  Barnet,  for 
the  purification  of  this  ammonia  effluent,  and 
is  now  working  at  a  number  of  gasworks. 
With  the  ammonia  gas  produced  by  boiling  as 
described  also  are  evolved  carbon  dioxide  and 
sulphuretted  hydrogen,  and  upon  absorption 
of  the  ammonia  by  acid  these  gases  remain, 
and  are  employed  for  the  purification  of  tbe 
waste  liquor.  The  liquor  enters  the  plant  at 
A.  The  solids  are  removed  in  B,  the  clear 
liquor  is  pumped  from  C  to  D  and  passes 
to  E.  The  waste  gases  from  the  liquor 
heater  of  the  sulphate  plant  enter  by  E  and 
leave  at  the  top,  passing  to  the  condenser  of 
the  sulphate  plant,  the  working  of  which  is  in 
no  way  interfered  with.  The  lime  is  pre- 
cipitated and  phenoloids  decomposed.  About 
three  volumes  of  air  are  mixed  with  the  waste 
gases  employed  by  means  of  the  injector 
shown,  a  separate  air  pipe  leading  to  the 
section  above  E.  The  liquor  re-enters  at  F 
and  passes  to  G.  A  large  volume  of  air  is 
injected  at  H,  leaving  at  I,  carrying  away 
phenoloids  and  other  liberated  impurities.  A 
condensate  containing  these  accumulates  at  J, 
and  thence  is  led  to  a  fire  K.  Cyanogen  com- 
pounds are  more  completely  removed  if  neces- 
sary by  replacing  L  with  a  tank  for  settling  out 
carbonate  of  lime,  and  introducing  a  small 


amount  of  vitriol  continously  at  F.  The 
liquor  passes  to  settling  tank  Af  and  filter  tanks 
N.  The  bacterial  effect  of  the  purified  effluent 
was  determined  with  sewage  effluent,  adding 
various  amounts  as  below  to  sewage,  incuba- 
ting five  hours  at  32°  C.  (by  0.  Hehner). 
"  Sewage  without  addition,  bacteria  per  c.c., 
2,419,000  ;  sewage  plus  4  %  effluent  bacteria 
per  c.c.,  2,337,000;  sewage  plus  6%  effluent 
bacteria  per  c.c.,  2,475,000 ;  sewage  plus  8  °/0 
effluent  bacteria  per  c.c.,  3,211,000;  sewage 
plus  12  %  effluent  bacteria  per  c.c.,  3,846,000. 

"  Up  to  12%  the  liquid  has  not  only  not  anti- 
septic action  on  bacteria  but  greatly  stimulates 
their  growth  and  development."  These  plants 
have  been  successfully  working  for  years  in 
works  which  have  been  compelled  to  cease 
working  their  ammonia  recovery  plant. 

The  cost  for  labour  and  material  are  nothing 
and  the  outlay  small. 

Gauging  Streams,  &c. — The  simplest 
way  of  ascertaining  the  flow  of  a  small  stream 
is  to  catch  the  water  in  a  vessel  of  known 
capacity  and  to  make  a  careful  note  of  the 
time  taken  to  fill  it.  Several  trials  should  be 
made  in  order  to  establish  a  mean.  Such  a 


FIG.  1. 

method  is,  necessarily,  only  applicable  to  very 
small  supplies.  For  measuring  larger  volumes 
of  water,  gauging  with  a  weir  is  the  most 
reliable  system.  The  weir  is  formed  by 
damming  the  stream  with  a  plank  and  allowing 


203 


GAU 


ENCYCLOPAEDIA   OF 


GAU 


the  water  to  flow  freely  over  a  rectangular 
notch  cut  in  the  same  (see  Figs.  1  &  2). 
The  width  of  the  notch  should  not  exceed 
two-thirds  that  of  the  stream  and  its  depth 
must  be  sufficient  to  pass  all  the  water  that 
is  to  be  measured.  The  edges  of  the  notch 
should  be  bevelled,  as  shown,  and  any  leakage 
at  the  sides  or  bottom  of  the  plank  prevented 
by  the  use  of  puddled  clay.  The  depth  of 
water  flowing  over  the  sill  should  not  be 
more  than  a  quarter  of  the  total  depth  on 
the  up-stream  side,  and  the  dam  should  be 
high  enough  to  form  a  reservoir  through 
which  there  is  no  perceptible  current.  The 
bottom  of  the  notch  must  be  set  truly 
horizontal  by  means  of  a  spirit  level. 


FIG.  2. 

A  gauging  stake  is  then  driven  in  until  its 
top  is  exactly  level  with  the  sill  of  the  notch  ; 
this  stake  should  be  placed  in  the  still  water 
well  away  from  the  depression  that  occurs  in 
the  vicinity  of  the  overfall,  so  that  the  true 
depth  of  the  flowing  section  may  be  measured. 
A  thin  rule  should  be  used  with  its  edge  in 
the  direction  of  the  current.  The  quantity  of 
water  passing  over  the  weir  may  be  calculated 
with  sufficient  accuracy  for  all  practical  pur- 
poses by  the  following  formula  : — 

Q  =  4-81  L.  \/T3 

Q  =  Discharge  over  notch  in  cubic  feet  per 

minute. 

L  =  Length  of  notch  in  feet. 
h  =  Height  of  water  above  top  of  stake  in 

inches. 
A  weir  with  a  V-shaped  notch  is  easier  to 


construct,  and,  as  the  breadth  of  the  over- 
flow bears  a  constant  proportion  to  the  height, 
is  preferable  to  a  level  notch  when  the  volume 
of  water  is  sufficiently  small  to  permit  its 
employment.  The  notch  must  be  an  exact 
right  angle,  with  its  (inverted)  apex  level  with 
the  top  of  the  stake.  The  edges  should  be 
bevelled  on  the  outfall  side  and  the  weir 
formed  in  the  same  manner  as  for  the  rectan- 
gular notch.  The  discharge  may  be  calculated 
by  the  following  formula : — 

D  =  1-978  k2  VTT 
D  =  Discharge  in  gallons  per  minute. 
h  =  Height  of  water  above  top  of  stake  in 

inches. 

If  the  stream  is  too  wide,  or  its  banks  are 
unsuited  to  the  use  of  a  weir,  a 
fairly  reliable  estimate  of  the  flow 
may  be  arrived  at  if  the  average 
cross-sectional  area  of  the  stream 
and  the  velocity  of  the  water  are 
known. 

The  velocity  of  the  water  may  be 
ascertained  by  observing  the  mean 
time  that  a  float  (such  as  a  bottle 
sunk  to  the  cork)  occupies  in  travel- 
ling between  two  points — say  100 
feet  apart.  Several  experiments 
should  be  made  in  the  most  uniform 
section  of  the  stream  that  can  be  found, 
and  the  float  should  be  cast  into  the  water 
well  above  the  starting  point.  Owing  to 
the  friction  of  the  sides  and  bottom  of  the 
channel  the  velocity  of  the  water  will  not  be 
uniform  ;  the  actual  quantity  passed  will  be 
less  than  that  indicated  by  the  float,  by  an 
amount  which  depends  upon  the  material  of 
which  the  channel  is  composed  and,  to  some 
extent,  its  shape.  The  formula  may  be  stated 
thus  :— 

_  DEL 
q~~      T  K  ' 

q   =  Flow  in  cubic  feet  per  second. 
D  =  Average  depth  of  wetted  channel  in  feet. 
B  =  Average  breadth  of  ditto. 
L  =  Distance  traversed  by  float  in  feet. 
T  =  Average    time,    in    seconds,    taken   by 
float  from  point  to  point. 


204 


GEL 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


GER 


K  •=•  Co-efficient  =  '65  for  rocky  stream  beds. 
=  '70     for     small      earthen 

channels. 

=  '80  for  large  ditto. 
=  '85  for  smooth  conduits. 

The  results  by  this  method  are  only  approxi- 
mate, and  it  should  not  be  resorted  to  when 
others  are  admissible. 

The  mean  velocity  of  a  stream  can  be  more 
reliably  determined  by  taking  observations  at 
various  points  with  a  current  meter.  This 
usually  consists  of  a  small  screw  propeller 
driven  by  the  water  and  combined  with  a 
revolution  counter,  the  relation  between  the 
revolutions  of  the  screw  and  the  velocity  of 
the  current  being  established  by  drawing  it 
through  still  water  at  various  speeds. 

When  it  exists,  and  permits  a  free  discharge 
to  the  water,  a  sluice  affords  a  very  convenient 
method  of  obtaining  the  volume  of  a  stream. 
The  gate  must  be  opened  until  it  exactly 
passes  all  the  water  coming  down  the  stream. 
The  breadth  and  height  of  the  opening  and 
the  depth  from  the  surface  of  the  water  to  the 
centre  of  the  orifice  must  then  be  carefully 
measured.  The  discharge  may  be  found 
thus  : — 

q  =  8-025  A  K,  V~H 

q  =  Quantity    of    water    in    cubic   feet    per 

second. 

A  =  Area  of  orifice  in  square  feet. 
K  =  Coefficient  =  '62  for  a  sluice  without  side 

walls. 

=  '96  for  a  sluice  with  walls 
in  a  line  with  the 
opening. 

H  =  Head  =  surface  of  water    to   centre  of 
orifice  in  feet. 

For  cylindrical  extensions,  of  the  same 
diameter  as  the  orifice,  but  with  a  length  rang- 
ing from  twice  to  sixty  times  the  diameter, 
K  varies  from  '82  to  '62.  E.  L.  B. 


Gel,  a  term  introduced  by  Graham  to 
denote  the  gelatinous  result  of  the  coagulation 
of  Colloidal  Matters  (q.  v.}. 


"Germs"  of  Disease. — Numerous  dis- 
eases are  now  known  to  be  due  to  the  presence 
in  the  system  of  very  minute  forms  of  animal 
and  vegetable  life,  popularly  spoken  of  as 
"germs."  Many  of  the  specific  infectious 
diseases,  of  which  Professor  Osier,  in  his 
"  Principles  and  Practice  of  Medicine," 
enumerates  twenty-five,  are  known  to  be  due 
to  bacteria,  and  it  is  probable  that  all  of  them 
are  due  to  similar  organisms.  Proof  is  at 
present  wanting  in  many  cases,  and  in  some 
it  may  ultimately  be  found  that  the  "  germ  " 
is  an  animal  rather  than  a  vegetable  parasite. 
Thus  malarial  fever  was  for  long  considered 
to  be  an  infectious  disease  allied  to  typhoid 
fever,  but  recent  researches  have  proved  that 
the  specific  organism  is  a  sporozoa,  and  that 
human  beings  are  infected  by  the  bite  of  cer- 
tain mosquitoes,  in  the  bodies  of  which  the 
microscopic  animal  undergoes  one  stage  of  its 
singular  development.  Bacteria  are  parasitic 
fungi,  and  it  is  believed  that  some  may  be  so 
small  as  to  be  beyond  the  limit  of  visibility 
under  the  highest  possible  magnifying  power 
of  the  microscope.  Even  with  the  highest 
available  power  they  appear  like  single  cells, 
ranging  in  form  from  a  sphere  to  a  short 
cylindrical  rod.  According  to  their  forms 
they  are  usually  divided  into  three  groups. 
Cells,  spherical  or  nearly  so — Coccii  cells, 
rod-shaped  and  straight  or  but  slightly 
curved — Bacilli  cells,  elongated  and 
twisted  or  forming  spiral  threads — 
Spirilla. 

Erysipelas,  pneumonia  (certain  forms  of), 
gonorrhoea,  Malta  fever  and  cerebrospinal 
meningitis  are  the  chief  diseases  known  to 
be  due  to  cocci,  anthrax,  plague,  typhoid  fever, 
dysentery  (certain  forms  of),  influenza,  diph- 
theria, tetanus,  tuberculosis,  leprosy  and 
glanders  are  due  to  bacilli,  while  the  germ 
of  cholera  is  a  spirillum.  Many  of  these 
bacteria  can  be  made  to  vary  enormously  in 
virulency  by  different  methods  of  cultivation, 
and  when  introduced  into  the  system  they 
may  or  may  not  cause  disease.  (Vide  "  ZYMOTIC 
DISEASES.")  The  mere  presence  of  these  germs 
is  not  sufficient  to  account  for  their  effect,  and 


205 


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ENCYCLOPAEDIA   OF 


GUL 


in  the  majority  of  cases  there  is  110  doubt  that 
these  effects  are  due  to  specific  poisons, 
"  toxins,"  which  the  germs  produce  during 
their  growth.  They  may  enter  the  system 
through  abrasions  of  the  skin  or  internal 
mucous  membrane,  through  the  lung  tissue,  or 
through  the  alimentary  canal.  They  may 
multiply  upon  the  surface  of  the  tonsils  and 
by  their  growth  destroy  the  tissue  beneath 
and  so  gain  access  to  the  system.  The  effects 
produced  vary  considerably,  as  will  at  once  be 
realised  by  comparing  the  history  of  a  person 
suffering,  for  example,  from  typhoid  fever  due 
to  the  typhoid  bacillus  w7ith  that  of  one  suffer- 
ing from  phthisis  due  to  the  bacillus  of  tuber- 
culosis. Many  of  these  germs  are  capable  of 
being  grown  outside  the  human  body  on 
suitable  media.  Most  of  them  are  easily 
destroyed  by  a  temperature  of  80°  C.,  but  a 
few,  such  as  the  bacillus  of  tetanus  and  of 
anthrax,  will  withstand  a  temperature  of 
100°  C.  for  a  short  time.  These  latter  are 
spore-bearing  bacilli.  The  majority  are  non- 
spore  bearing  and  multiply  by  simple  fission. 
Those  producing  spores  only  do  so  under 
certain  circumstances,  and  these  spores  are 
much  more  resistant  than  the  bacilli,  and  may 
survive  under  conditions  which  rapidly  prove 
fatal  to  the  bacilli  themselves.  (See  "  ZYMOTIC 
DISEASES  "  and  "BACTERIA.")  J.  C.  T. 

Goux  Tub  System. — This  is  one  of  the 
conservancy   methods    of    dealing   with   the 


involves  the  lining  of  the  tub  or  pail  with 
some  absorbent  material  with  the  object  of 
securing  dryness,  retarding  decomposition, 
and  preventing  nuisance.  The  size  and  class 
of  pail  is  shown  in  the  accompanying  figure, 
and,  by  the  employment  of  the  mould,  also 
illustrated,  absorbent  materials  such  as  saw- 
dust, shavings,  shoddy,  stable  litter,  leaves, 
or  other  like  substances,  are  compressed  into 
the  form  of  a  lining  some  6  in.  in  thick- 
ness, into  which  the  excreta  is  received. 
When  the  pails  are  received  for  collection  the 
upper  portion  of  the  lining  is  broken  up  and 
scattered  over  the  contents  with  the  object  of 
rendering  the  same  as  free  from  odour  as 
possible. 

Grease  Traps.— Surface  traps  or  gullies 
designed  to  prevent  also  the  passage  of  grease 


Absorbent  lining  of 
sou/dust,  shavings  etc 


collection  of  human  excreta,  and  has  been  in 
use  at  Halifax  for  many  years.   The  principle 


Grease  Trap. 

from  scullery  sinks  into  drains.  These 
traps  are  usually  provided  with  a  dipped  inlet 
and  outlet  and  offer  a  large  water  area  for  the 
cooling  of  the  grease.  Frequently  they  are 
supplied  with  a  bucket  or 
tray  which  when  lifted  out 
of  the  trap  removes  the 
solidified  grease  from  it. 
Grease  traps  are  liable  to 
give  rise  to  nuisance  and  are 
best  avoided  if  possible. 

Gullies,  or  Surface 
Traps.  —  These  are  traps 
placed  on  the  inlet  end  of 
drains  provided  for  the  re- 
ception of  rain  and  waste 
water.  Their  use  is  to  prevent  the  issue  of 
drain  air  at  those  points.  The  sanitary  forms 


206 


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MUNICIPAL  AND   SANITARY  ENGINEERING. 


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Gully. 


of  these  traps  are  of  siphon  shape,  and  that 
illustrated  is  typical  of  them  all.  They  vary 
mostly  as  regards  the  form  of  inlet,  and  are 
available  with  or  without  branches  for  the 
reception  of  waste  pipes, 
&c.  Some  are  provided 
with  flushing  rims,  that 
being  a  convenient  method 
of  connecting  a  flushing 
tank  to  drains.  In  selecting 
gullies,  preference  should 
be  given  to  those  which 
provide  a  sufficient  seal  with  a  minimum 
quantity  of  water,  and  which  have  a  good 
base,  as  the  latter  will  greatly  facilitate 
proper  fixing.  Rain-water  and  waste- water 
pipes  may  be  arranged  to  discharge  into  the 
gullies  either  above  or  under  the  gratings  of 
the  traps,  but  should  in  all  cases  do  so  above 
the  water  level. 

Head  (pressure,  loss  of). — Water,  or 
other  liquids,  when  flowing  through  pipes 
encounter  a  resistance  due  to  friction  and, 
to  a  slight  extent,  the  viscosity  of  their 
particles. 

The  pressure  required  to  overcome  this 
resistance  and  to  propel  the  liquid  through 
the  pipe,  is  conveniently  expressed  in  the 
terms  of  the  head  or  height  of  the  liquid  that 
would  correspond  with  that  pressure. 

The  friction  of  water  in  pipes  increases 
nearly  as  the  square  of  its  velocity  and  directly 
as  the  length  of  the  pipe  ;  but  it  is  inversely 
proportional  to  the  hydraulic  mean  radius  of 
the  same  (i.e.,  the  cross-sectional  area  divided 
by  the  circumference). 

Any  alteration  in  the  direction  of  the  flow 
by  bends  or,  more  particularly  elbows, 
increases  friction,  and  the  latter  should  always 
be  avoided  if  possible.  Sudden  contractions 
or  enlargements  are  also  undesirable,  in  that 
they  create  eddies.  The  condition  of  the 
interior  surface  of  the  pipe  is  likewise  an 
important  factor,  the  friction  in  encrusted 
pipes  being  about  twice  that  in  perfectly  clean, 
smooth  pipes,  added  to  which  there  is  a  further 
loss  by  reduction  of  area.  The  loss  of  head 


in  clean  cast-iron  coated  pipes  may  be  found 
as  follows : 

H=         V*L 

K2  X  -25ZT 

H  =  Head  in  feet. 

V  =  Velocity  of  water  in  feet  per  second. 

D  =  Diameter  of  pipe  in  feet. 

L  =  Length  of  pipe  in  feet. 

K  =  A  co-efficient  depending  upon  the  size 
of  the  pipe,  which  varies  as  follows  :— 
Diain.  of  pipe 

in  feet  ..  -25  -5  '75  1-0  1'25  1-5  1'75  2'0 
Value  of  K  .  .  70  86  97  106  113  118  121  123 
Diam.  of  pipe 

in  feet      . .    2"5    3'0    3'5     4'0 
Value  of  K  . .   127    131    135    138 

Similarly  V  will  be  equal  to  K  \/  2  x  - 

4        L' 

The  discharge  in  cubic  feet  per  second 
will  obviously  be  equal  to  the  sectional  area 
of  the  pipe  in  feet  multiplied  by  V.  (See 
"FLOW  OF  WATEK  IN  PIPES"  and  "  HYDRAULIC 
MEMORANDA.")  E.  L.  B. 

Heat,  Utilisation  of. — (See  "DESTRUC- 
TORS.") 

Heating1.  —  Open  Fires  —  Hot  Water  and 
Steam  Heating  —  Hot  Water  Low-Pressure 
Systems — Two-pipe  Method — One-pipe  System 
—  Hot-water  Boilers  —  Selection  of  Boilers  — 
Radiating  Surfaces  for  Ordinary  and  Horti- 
cultural Buildings — High  Pressure  or  Perkins 
System  —  Heating  Water  by  Steam  —  Steam 
Heating  —  Low  Pressure  —  Vacuum  Systems  — 
Ventilation  and  Heating — Air  Warming-stoves. — 
Ideally  the  warming  of  rooms  and  buildings 
is  to  raise  and  maintain  the  air  and  surfaces 
at  an  even  and  agreeable  temperature  through- 
out, with  a  minimum  of  fuel  and  attention, 
and  without  adding  impurities  to  the  air, 
creating  draughts,  or  unduly  robbing  the  air 
of  its  invigorating  properties  and  humidity. 

OPEN  FIRES  possess  a  cheerful  appearance. 
Bodily  warmth  may  be  quickly  absorbed, 
ventilation  is  assisted,  and  the  fire  is  available 
for  domestic  purposes.  On  the  other  hand, 
there  is  considerable  disproportion  of  heat 
emitted  to  fuel  consumed;  much  dirt  and 


207 


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ENCYCLOPEDIA   OF 


HEA 


labour  is  involved,  and  the  room,  especially  if     hot-water    heating    may   be     sub-divided   as 


large,  is  not  equably  warmed.  Although  open 
fires  provide  perhaps  the  most  healthy  means 
of  warming  rooms,  their  use  in  towns  adds 
seriously  to  the  pollution  of  the  atmosphere. 

HOT  WATER  AND  STEAM  HEATING. — A  more 
equable  temperature  may  be  maintained  with 
a  considerable  saving  of  fuel  by  warming  the 
house  or  building  with  hot  water  or  steam. 

HOT-WATER  LOW-PRESSURE  SYSTEMS. — In 
low-pressure  systems  an  open  pipe  is  carried 
above  the  supply  cistern,  the  pressure  being 
thereby  limited  to  the  head  of  water.  A 
boiler  is  placed  below  the  rooms  to  be  warmed, 
and  one  or  more  pipes — flow  and  return  pipes 
— carried  along  or  returned  in  the  direction  in 
which  heat  is  to  be  emitted.  "  Flow  "  pipes 
leave  the  top  of  boiler  and  ascend,  permitting 
convection  currents  to  rise  therein,  whilst 
"return"  pipes  descend,  the  water  therein 
returning  by  gravitation  to  the  boiler,  entering 
it  near  the  bottom  to  ensure  circulation 
throughout.  The  system  should,  as  far  as 
possible,  be  arranged  to  obtain  the  maximum 
vertical,  as  opposed  to  horizontal  piping,  the 


FiG.l. — One-pipe  Steam  System. 

size  of  mains  and  branches  proportioned  to 
the  radiating  surface  required,  and  a  boiler  of 
ample  proportions  provided.  Low-pressure 


follows : — 

Two- PIPE  METHOD. — Flow  and  return  pipes 
are  carried  along  side  by  side,  the  branches  to 


FIG.  2. — Two-pipe  Hot-water  System. 

the  different  floors  and  radiators  being  taken  off 
the  flow  and  return  pipes.  Objections  to  this 
method  are,  (a)  two  pipes  must  be  run  to 
every  part  of  the  premises  to  be  heated  ; 
(b)  radiators  being  connected  to  both  flow 
and  return,  short  circuiting  may  result. 

ONE-PIPE  SYSTEM. — This  system  has  for 
its  principle  the  running  of  one  or  more 
large  circuit  mains.  Each  main  leaves  the 
top  of  the  boiler  and  rises  as  vertically  as 
possible  to  its  highest  point,  returning  to 
the  boiler  by  way  of  the  radiators.  Branches 
and  flow  and  return  connections  are  taken 
from  the  return  main — in  some  cases  a  few 
may  be  taken  from  the  flow — the  same  as  if 
directly  off  the  boiler ;  flow  connections 
from  top  of  main  and  return  connections 
from  side  of  main  furthest  from  boiler. 
As  single  mains  are  used  they  require  to  be 
larger  than  with  the  two-pipe  system  ;  the 
volume  of  water  to  be  carried  is,  however, 
practically  the  same.  Advantages  of  the  "  one- 
pipe  system"  are,  short-circuiting  is  impos- 
sible, and  generally  the  constructional  cost 
is  lower. 


208 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


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to  Other [ 
Work 


V 


A  modification  of  the  "  one-pipe  system," 
known  as   the   "overhead  or   drop    system," 
is   largely   adopted    in    buildings   possessing 
similarly  planned  floors.     The  main  pipe  is 
carried  direct  to  the  top  floor  or  attic  above, 
distributing  branches   being    here   taken   off 
and    "dropped"    to   return    to    the    boiler. 
Eadiators    are    connected    to    the     "  drop " 
pipes,  the   feed  at  the   top 
and  return  at  bottom.     No 
air  cocks  are  required,  but 
an  expansion  cistern  or  tank 
through   which  the  whole 
system  is  vented  is  required 
above   the   highest   part   of 
main.     With  this  system  a 
more    rapid    circulation    is 
obtained,  and  smaller  pipes 
may  be  used. 

HOT-WATER  BOILERS. — The 
success  of  any  hot -water 
apparatus  is  dependent 
upon  the  boiler.  The  amount 
of  radiating  surface,  in- 
cluding mains  and  branches, 
should  be  ascertained,  and  a 
boiler  of  ample  proportions 
provided.  Uniform  rating 
of  boilers  is  much  needed. 
A  common  basis  is  to  allow 
1  sq.  ft.  of  boiler  surface  to 
35  ft.  of  4-in.  pipe.  This 
ratio  is  reduced  to  1  ft.  to 
25  ft.  by  at  least  one  maker. 
Regard  should,  however,  be 
had  to  the  fact  that  the 
efficiency  of  boiler  surface 
varies  with  its  position  rela- 
tive to  the  fire.  A  better 
method  is  to  list  the  boiler 
B.T.U.  per  hour.  This  should  be  based 


calculated  by  multiplying  the  heat  emission 
per  square  foot  of  radiating  surface  by  the 
total  area  of  radiators,  mains  and  branches. 
The  heat  emission  in  B.T.U.  of  hot- 
water  radiators  and  pipes  varies  from  about 
200  to  150  per  hour  with  the  temperature 
of  the  air  about  them  at  60°  F.  A  reliable 
estimate  of  boiler  power  required  may  be 


1 


I 


Other 
Work 


'eft/rn  from 
Other   Work 


on  an  apparatus  working  under  normal  con- 
ditions. The  practical  test  in  all  cases  is  the 
fuel  consumption  and  heat  transmission  when 
banked  to  last  a  specified  time.  As  the  boiler- 
capacity  should  always  be  at  least  equal  to  the 
radiator  emission  required  to  properly  warm 
the  various  rooms,  &c.,  the  capacity  may  be 
M.S.B.  209 


FIG.  3. — Hot  Water  Overhead  or  Drop  System. 

capacity  in  obtained  by  multiplying  the  total  area  of 
radiators,  uncovered  mains  and  branches  [by 
180,  the  result  giving  the  required  capacity 
in  B.T.U.  per  hour. 

SELECTION  OF  BOILERS. — Brick-set  boilers 
are  now  giving  way  to  "independent"  types. 
These  are  compact,  occupy  less  space,  and  are 
more  easily  examined  and  repaired.  Cast-iron 
sectional  boilers  are  largely  used.  They 

p 


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ENCYCLOPAEDIA  OF 


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possess  many  advantages,  and,  with  proper 
care,  should  last  longer  than  wrought-iron, 
but  are  somewhat  more  complicated,  and  the 
thickness  of  the  castings  are  not  always 
uniform  throughout.  In  a  well-designed  type 
of  this  class  a  large  heating  surface  is  exposed 
to  the  fire  and  hot  gases.  The  grate  area  is 
well-proportioned,  and  the  front  well  fitted  for 
draught  regulation.  These  boilers  are  fairly 
economical  in  fuel. 

EADIATING  SURFACE  EEQUIRED. — This  may  be 
estimated  by  either  of  the  following  methods  : 
(1)  By  calculating  the  heat  in  B.T.U.  required 
to  raise  the  temperature  of  air  contained  in 
and  passing  through  the  apartment,  idus  the 
heat  lost  through  the  several  materials,  walls, 
windows,  &c.,  enclosing  the  room  (in  most 
cases  exposed  surfaces  only  need  be  considered), 
and  dividing  the  sum  of  the  whole  by  the 
B.T.U.  emitted  per  square  foot  of  radiating 
surface,  which  for  radiators  and  low  pressure 
hot  water,  to  maintain  a  temperature  of 
60°  F.,  may  be  taken  as  160°.  Owing  to 
leakage  of  air  through  ill-fitting  doors,  windows, 
&c.,  two  to  three  air  changes  per  hour  should 
be  allowed.  The  following  table  gives  the 
coefficient  in  B.T.U.  to  raise  the  temperature 
of  air,  also  the  heat  transmission  through 
walls/ &c.  The  calculation  is  in  B.T.U.  per 
hour  for  1°  difference  in  temperature  of  air, 
and  also  on  the  two  sides  of  the  walls,  &c. 

HEAT  LOSSES. 


Coefficient. 

Air 

.      ..   leu.  ft.    ..     -019  B.T.U 

4£  in.  Brick  wall 

.  .    1  sq.  ft.   .  .     -5 

9 

..     -35 

14       „ 

..     -27 

18       „ 

..      -23 

Single  windows 

..   1-03 

Double       ,, 

..      '48 

Single  skylights 

..   I'll 

Double        ,, 

..      -5 

Corrugated  iron  roofs 

..   2-17 

Ceilings  close  to  roof 

..     '32 

,,        with    good    air 

space 

..     -13 

Floors   (12  in.   concrete 

and  wood)    .  . 

•17 

,,        (wood  on  joists)     .  . 

..     -52 

Doors  1£  in.  thick 

..     -45 

To  ascertain  the  loss  in  B.T.U.  per  hour 
from  any  room  or  building,  multiply  the  air 


coefficient  in  table  by  the  cubic  capacity  and 
the  air  changes,  and  by  the  difference  between 
the  required  internal  and  the  external  tem- 
perature. To  this  must  be  added  the  sum  of 
the  products  of  the  different  surfaces  multi- 
plied by  their  respective  coefficients  and  by 
the  difference  between  the  external  and  in- 
ternal temperature.  Dividing  the  total  by  160 
gives  square  feet  of  radiating  surface  required 
to  maintain  a  temperature  of  60°  inside 
when  30°  outside.  Or  (2),  a  simplified  formula 
may,  in  ordinary  cases,  be  used.  The  formula 
by  W.  Jones,  based  on  a  lifelong  experience, 
is  easy  of  application  :  — 

FOR  ORDINARY  BUILDINGS  (not  horticul- 
tural). —  To  obtain  60°  inside  when  30°  out- 
side, and  water  170° 


= 
"6     r 


4. 

~1~ 


12        120  to  160*' 


S   = 

G  = 
W  = 
C  = 


Ft.   super  radiation  required  for  the 
stated  temperature. 
Ft.  super  glass. 
Ft.  super  exposed  wall. 
Cubic  capacity. 


l'  120  for  rooms  under  5,000  cu.  ft.  capacity. 
jjl40        „  5,000  to    25,000  „ 

1  150        „         25,000  to  100,000  „          „ 
(.160        >,         over  100,000  „          „ 

The  above  rule  assumes  the  loss  through 
doors,  walls,  and  windows  to  be  from  two  to 
three  changes  of  air  per  hour.  If  more  air 
changes  are  required,  add  cubic  capacity  -r- 
300  for  each  additional  change. 

FOR  HORTICULTURAL  BUILDINGS.  —  The  fol- 
lowing rule  by  W.  Jones  gives  the  feet  sup. 
radiating  surface  required  for  the  same  tem- 
peratures as  in  last  :  — 

Q-S,    E,     £. 
"  6  "r  12  ^  150* 

A  table  of  coefficients  for  use  with  other 
temperatures  is  given  in  "  Heating  by  Hot 
Water,"  by  W.  Jones.  No  rule  or  combination 
of  rules  will  be  applicable  to  every  case  ;  e.g.  an 
increased  amount  of  radiating  surface  will  be 
required  in  the  case  of  rooms  or  buildings 
exposed  to  severe  weather. 


210 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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HIGH  PRESSURE  OR  PERKINS  SYSTEM. — 
This  system  has  been  in  use  upwards  of  60 
years ;  its  use,  however,  is  not  nearly  so 


quickly  raised.  It  may  be  used  to  assist 
ventilation  (in  this  case  it  should  be  filled  with 
anti-freezing  liquid).  The  pipes  are  smaller 


extensive  as  the  low  pressure  system.     It  con-     and   neater   in   appearance.     The   system   is 


sists  of  a  series  of  very  strong  wrought-iron 

tubes — similar  to  hydraulic  tubes — usually  of 

-J  in.  bore,  screwed  together  with  right  and 

left    hand   threads.      One    of    the 

ends    of    the    tube   to    be    drawn 

together    is    tapered,    inside    and 

out,  to  a  conical  edge,  the  other 

end   being  trued   to    a    flat    face. 

Powerful    tongs   are     required    to 

draw  the  tubes  together,  the  actual 

joint   being  made   by  forcing   the 

coned   edge   into   the  flat    face  of 

the  opposite  pipe.     The  boiler  is 

coiled  of  the  same  description  and 

size  of  tube,  the  number  of  coils 

being  proportioned  to  the  quantity 

of     radiating     surface.       At    the 

highest  point  of  the  apparatus  is 

fixed   an   air   vessel  or  expansion 

pipe,  the  capacity  of  which   must 

be   carefully   proportioned    to   the 

quantity  of  water  contained  in  the 

apparatus.     Water  is  pumped  into 

the  apparatu^  from  a  point  near 

the    boiler  s,  until    it    reaches    an 

overflow   placed  at  the  bottom  of 

the  expansion  pipe.     The  overflow 

is    then    plugged,    the    apparatus 

being   hermetically    sealed.     It   is 

afterwards  tested  to  a  pressure  up 

to  3,000  Ibs.   per  sq.  in.     Owing 

to  the  apparatus  being  sealed,  the 

water   may  attain    a   temperature 

of  300°  to  600°,  being,  of  course, 

accompanied    by    high    pressure; 

and    the    expanded    water    compresses    the 

air    in    the    expansion    pipe.      Considerable 

experience    and    special   appliances    are    re- 


suitable  for  large  buildings  that  are  well 
ventilated.  The  disadvantages  are :  Repairs 
necessitate  the  calling  in  of  a  specialist,  pre- 


Automatic 
Steam   Control 
Vslve 


FIG.  4.— Vertical  Steam  Calorifier  with  Indented  Tube. 


ferably  the  erecting  firm.  The  high  tempera- 
ture of  the  pipes  often  produces  unpleasant 
smells,  due  to  the  burning  of  organic  matters 
quired  to  properly  erect  this  system;  but  present  in  the  air.  Pipes  must  be  kept  well 
although  the  apparatus  may  appear  to  be  away  from  woodwork.  The  system  is  specially 
highly  dangerous,  it  is  not  so  in  fact,  as  any  suitable  for  high  temperatures  such  as  are 
defect  manifests  itself  at  the  boiler  and  puts  required  for  laundry  purposes,  &c. 
the  fire  out.  Advantages  claimed  for  this  HEATING  WATER  BY  STEAM.— Where  a  steam 
system  are :  The  temperature  of  the  water  is  supply  is  available  the  building  may  be 

211  " 


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warmed  by  water  heated  by  contact  with 
steam-heated  surfaces,  or  by  allowing  steam 
to  pass  direct  into  the  water.  Warming  by 
steam-heated  surfaces  is  accomplished  by 
steam-heaters,  or  "  calorifiers,"  generally 
cylindrical  in  form,  which  takes  the  place  of 
the  hot  water  boiler,  connections  being  simi- 
larly made  thereto.  Inside  the  calorifier  there 
is  usually  a  coil  or  series  of  tubes  through 
which  the  steam  passes,  warming  the  water  in 
contact  with  the  outside  of  the  tubes.  The 
condensed  steam  is  or  should  be  ultimately 
returned  to  the  boiler. 


FIG.  5. — One-Pipe  Steam  Gravity  System. 

The  power  of  steam-heaters  or  calorifiers 
varies  with  the  temperature  of  steam  and  with 
the  form  of  tube  and  general  construction  ; 
1  ft.  super  of  steam-heated  tube  is  usually 
much  more  effective  than  an  equal  amount  of 
hot  water  boiler  surface.  Heating  by  the 
injection  of  steam  is  accomplished  by  means 
of  an  "  injector;"  the  issuing  steam  warms  the 
water  and  impels  the  same  along  its  course. 
There  is  an  amount  of  water  added  to  the 
apparatus  equal  to  the  steam  condensed, 
which  must  be  allowed  to  overflow,  and  then 
returned  to  the  boiler-house  for  use  in  the 
boiler.  These  systems  are  very  suitable  for 
large  institutions  with  a  central  heating  plant 
or  boiler-house. 


STEAM  HEATING. — Steam  is  extensively  used 
for  warming  public  buildings,  schools,  factories, 
&c.,  and  is  undoubtedly  superior  to  hot  water 
for  warming  in  conjunction  with  ventilation, 
as,  for  example,  in  the  plenum  systems.  It 
may  be  economically  employed  where  steam  is 
generated  for  other  purposes,  exhaust  steam 
being  frequently  and  advantageously  utilised. 
Where  a  steam  supply  is  not  available  and 
the  building  is  of  limited  dimensions,  as  for 
residential  purposes,  hot  water  possesses  many 
advantages  and  will  doubtless  continue  in 
favour  in  this  country.  Generally  speaking, 
a  steam  system  requires  a  skilled  atten- 
dant— a  matter  of  importance  in  small 
buildings  wrhere  the  caretaker  is  expected 
to  attend  to  the  apparatus.  Moreover, 
repairs  are,  if  anything,  more  costly,  and 
the  temperature  of  the  steam  (unless 
under  vacuum  systems)  is  not  easy  of 
manipulation.  For  large  buildings,  how- 
ever, steam  possesses  many  advantages. 
Steam  in  condensing  gives  up  its  latent 
heat — approximately  966  B.T.U.  per  pound, 
which  quantity  of  heat  is  dissipated  by  the 
pipes  of  radiators  before  the  steam  is 
entirely  condensed.  The  latent  heat  is  for 
practical  purposes  the  same  for  all  pres- 
sures, and  no  useful  purpose  is  served  by 
working  at  high  pressure ;  in  fact,  the 
reverse  is  the  case,  owing  to  the  higher 
temperature  of  the  pipes,  &c.,  burning 
up  organic  matter  in  the  air,  causing  un- 
pleasant smells,  and  also  robbing  the  air 
of  humidity.  In  a  properly  erected  steam- 
heating  system,  the  steam  should  be  carried 
to  the  radiators  with  a  minimum  of  con- 
densation and  be  there  dissipated.  The 
water  of  condensation  should  be  properly 
drained  without  interfering  with  the  flow  of 
steam,  and  be  directly  or  ultimately  returned 
to  the  boiler.  Adequate  provision  should  be 
made  for  the  escape  or  removal  of  air  from 
the  apparatus.  The  system  should  be  free 
from  noise,  and  the  steam  generated  and 
maintained  with  a  minimum  of  fuel  and 
attention. 
LOW-PRESSURE — ONE-PIPE  GRAVITY  SYSTEM.— 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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One  or  more  large  circuit  mains  are  used,  the 
highest  point  being  practically  directly  over 
the  boiler ;  from  here  the  main  descends 
until  it  returns  to  the  boiler,  entering  below 
the  water-line.  Single  connections  are  taken 
off  the  main  to  supply  radiators.  As  the 
water  returns  to  the  boiler  by  gravitation, 
little  attention  is  required,  especially  when  a 
good  form  of  automatic  damper  is  fitted,  to 
control  the  temperature  of  steam  by  draught 
regulation.  A  little  water  is  periodically 
added  to  the  boiler  to  replace  any  slight 
escape  of  steam.  This  is  the  cheapest  system 
to  erect,  and  when  properly  executed  is 
entirely  satisfactory. 


the  admission  of  only  the  maximum  amount 
of  steam  that  the  radiator  will  condense  when 
the  controlling  valve  is  full  open.  As  the 
supply  of  steam  is  reduced,  so  will  a  propor- 
tionate amount  of  radiator  surface  be  in  use. 
A  boiler  is  placed  in  a  cellar  or  pit,  a  tank 
being  placed  about  two  metres  above  the 
ordinary  water-line  of  boiler.  Two  pipes 
connect  the  tank  to  the  boiler,  one  being  taken 
from  the  bottom  of  tank  and  connected  to 
bottom  of  boiler  to  ensure  a  return  of  con- 
densed water ;  the  other  pipe — the  "  safety 
pipe  " — connects  the  tank  to  the  boiler  at  a 
point  situated  a  few  inches  'below  the  normal 
water-line.  This  pipe  projects  into  the  tank 


I, 


CE) 


I 


Wat&r  Line  -  -  - 


FIG.  6. — Two-Pipe  System,  Low  Pressure  Steam. 

LOW-PRESSURE—  TWO-PIPE  SYSTEM  WITH  WET     to  allow  sufficient  capacity  beneath  its  end  for 

water  to  return  to  the  boiler.  An  open  pipe 
is  taken  from  the  top  of  the  tank  and  carried 
beneath  the  fire  bars.  The  main  steam  pipe 
leaves  the  top  of  the  boiler  whence  it  gradually 
descends  as  in  previous  systems ;  the  end, 
however,  terminates  in  a  siphon,  the  height 
of  which  should  provide  a  water  column  equal 
to  the  maximum  boiler  pressure.  The  end  of 
the  siphon  is  carried  along,  gradually  falling 
until  it  enters  the  safety  tank  above  the  level 
of  water  therein.  Return  pipes  from  radiators 
are  connected  to  the  return  pipe  from  the 
siphon  and  the  ends  of  radiators  are  open  to 
the  atmosphere,  the  water  of  condensation 
being  returned  to  the  boiler  via  the  safety 
tank.  Advantages  of  this  system  are:  (a), 
that  small  pipes  may  be  used  to  supply 


RETURN. — The  highest  point  is  practically 
directly  over  the  boiler ;  from  here  it  gradually 
falls  until  the  last  radiator  is  passed,  when  the 
main  at  once  drops  below  the  water-line  of 
boiler,  returning  to  the  boiler  at  that  level. 
Two  connections  are  required  to  radiators,  the 
inlet  from  steam  main,  the  outlet  through 
which  condensed  water  flows  being  taken 
direct  to  the  return  pipe,  the  end  being  sub- 
merged. Care  should  be  taken  that  con- 
nections between  two  or  more  returns  are 
made  below  the  water-line  of  boiler.  This 
system  is  more  costly  to  install,  but  is  held  by 
many  to  be  more  silent  than  the  "  one-pipe." 
OPEN-PIPE  SYSTEM. — This  system  is  largely 
used  in  France,  but  is  not  common  in  this 
country.  It  has  for  its  principle  of  operation 


213 


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ENCYCLOPAEDIA  OF 


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radiators  ;  (&),  the  supply  of  steam,  and  con- 
sequently the  temperature  of  the  apartment, 
may  be  regulated  ;  (c),  its  free  discharge  of 
air ;  (d),  its  noiselessness  and  low  steam  pres- 
sure. The  use  of  an  automatic  damper  regu- 
lator is  indispensable. 

VACUUM  SYSTEMS. — Vacuum  systems  may  be 
used  with  live  or  exhaust  steam.  These 
systems  have  for  their  principle  the  removal 
of  air  from  the  apparatus,  and  the  creation  of 
a  partial  vacuum  which  permits  the  steam  to 
more  freely  enter  and  flow  to  all  parts  of  the 


valve,  which  automatically  opens  when  the 
apparatus  is  cold,  but  closes  when  in  contact 
with  steam,  thus  preventing  the  passing  of 
steam  to  the  condensed  water  pipes  and  mains. 
Fig.  8  shows  a  small  installation  having 
only  one  radiator  (2)  and  one  coil  (3) ,  which 
may  be  termed  the  essential  components  of  a 
vacuum  system  of  any  size.  This  small 
apparatus  is  supposed  to  be  supplied  either  by 
live  steam  from  the  boiler  on  the  right,  or  by 
exhaust  steam  from  the  engine  on  the  left, 
since  either  or  both  together  can  be  used  in  a 


RETURN 


WATER  LINE- 


..  i_ 


SAFETY  TANK 


SAFETY   PIPE 
RETURN 


FIG.  7. — Open-Pipe  System,  Low  Pressure  Steam. 
system.      The   whole   of    the   latent   heat  of     vacuum  system.     The  live  steam  would  first 


the  steam  is  given  off  in  the  radiator,  and  the 
steam  temperature  may  be  regulated.  One  of 
the  most  popular  systems  is  that  patented  by 
Warren  Webster  &  Co.,  of  America,  the 
licensees  in  this  country  being  the  Atmo- 
spheric Steam  Heating  Co.,  Ltd.  A  brief 
description  is  as  follows  : — A  pressure-reducing 
valve  is  fitted  to  reduce  the  pressure  of  steam 
entering  the  system  to  about  J  Ib.  per  square 
inch.  A  vacuum  pump  is  fitted  to  the  end 
of  the  condensation  main  to  extract  both  the 
air  and  the  water  of  condensation.  On  the 
outlet  of  radiators  is  fitted  a  therrnostatic 


pass  through  a  reducing  valve  (6)  and  a  main 
valve  (10),  and  the  exhaust  steam  through  a 
grease  separator  (7)  and  main  valve  (9), 
before  reaching  the  rising  pipe  supplying  the 
radiation.  On  each  unit  of  radiation  there 
would  be  an  automatic  valve  (5)  on  the  outlet, 
and  a  hand  control  valve  (4)  on  the  inlet,  as 
well  as  a  similar  automatic  valve  (8)  to  drain 
the  main  and  riser,  and  so  keep  the  apparatus 
clear  of  water.  From  the  automatic  valves 
(5  and  8),  small  pipes  would  be  taken  into  the 
main  return  or  condense  main,  at  the  end  of 
which  is  placed  the  vacuum  pump  (1).  In 


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MUNICIPAL  AND   SANITAEY  ENGINEEEING. 


HEA 


the  working  of  such  an  apparatus  the  vacuum 
pump  would  be  first  started,  and  would  ex- 
haust the  air  from  all  mains,  radiators,  &c., 
through  the  automatic  valves,  so  that  when 
steam  was  admitted  a  partial  vacuum  (average 
not  more  than  10  in.)  would  everywhere  pre- 
vail, and  the  only  work  required  of  the  steam 
would  be  that  of  imparting  its  heat  to  the 
heating  surfaces  by  condensation.  Under 
these  circumstances  it  is  clear  that  a  very 
quick  circulation  of  the  steam  to  the  furthest 
limits  of  the  apparatus  is  attained.  The 
function  of  the  automatic  valves  is  important ; 


the  future.  In  fact,  it  may  be  said  that 
vacuum  systems  and  rapid  circulation  hot 
water  (low  pressure),  are  now  generally 
favoured  by  heating  engineers. 

VENTILATION  AND  HEATING. — The  heating 
and  ventilation  of  rooms  or  buildings  should 
always  be  considered  in  combination.  Where 
a  room  is  warmed  by  hot  water  or  steam, 
ventilation  may  be  obtained  or  supplemented 
by  the  use  of  ventilating  radiators,  the  air 
passing  through  a  grating  in  the  wall  behind 
the  radiator,  being  warmed  by  contact  there- 
with. Another  method,  but  which  is  open  to 


FIG.  8. — Yacuum  System. 


they  prevent  "  short  circuiting  "  of  the  steam 
into  the  vacuum  maintained  return  main, 
which  itself  would  tend  to  destroy  the  vacuum, 
and  so  secure  that  no  steam  shall  be  wasted. 
Where  exhaust  steam  is  available  for  use,  a 
back  pressure  valve  (11)  on  the  exhaust  pipe 
is  required  to  seal  the  apparatus.  This  is 
generally  adjusted  to  open  at  J  Ib.  pressure. 
Gauges  (12)  are  set  up  to  indicate  the  pressures 
in  the  steam  and  return  mains  respec- 
tively. Among  the  advantages  of  a  vacuum 
system  may  be  mentioned  :  perfect  circu- 
lation, absence  of  noise,  controllability  of 
temperature,  economy  in  working  and  main- 
tenance. The  system  has  recently  been 
installed  in  many  important  public  buildings, 
and  will  undoubtedly  be  extensively  used  in 


objection  on  the  score  of  cleanliness,  is  the 
placing  of  a  heating  battery  under  the  floor, 
encased  in  sheet  iron  ;  air  passes  through  a 
grating,  and  is  warmed  by  the  heating  battery, 
thence  passing  into  the  room.  In  plenum 
systems  it  is  usual  to  warm  the  air  at  a  point 
near  the  fan,  the  air  being  either  forced  or 
drawn  through  the  battery  of  heating  pipes. 
A  much  larger  quantity  of  heating  surface 
is  required  with  systems  designed  to  aid  or 
be  used  in  connection  with  ventilation.  (See 
"  VENTILATION.") 

WARMING  BY  HOT  AIR  FURNACES  OR  CALORI- 
FIERS. — The  hot  air  furnace  generally  takes 
the  form  of  a  cast-iron  stove,  with  its  back 
corrugated  or  arranged  with  a  number  of 
fins  or  gills.  The  stove  is  placed  below  the 
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ENCYCLOPAEDIA   OF 


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rooms  and  generally  set  in  brickwork.  The 
air  to  be  warmed  is  conveyed  in  pipes  to  the 
furnace  and  heated  by  passing  over  the 
corrugated  surface  or  gills,  being  afterwards 
conveyed  to  the  different  rooms  by  means  of 
pipes  or  ducts.  As  this  system  brings  in 


system  are  :  (a)  low  cost  of  construction  ; 
(b)  as  fresh  warm  air  is  introduced,  ventilation 
is  necessary,  and  (c)  the  floor  space  of  the 
room  is  not  interfered  with.  On  the  other 
hand,  the  fuel  consumption  is  excessive,  and 
the  temperature  of  the  furnace  frequently 


FIG.  9. — "  Beck  "  Eapid  Circulation  Hot  Water  Apparatus. 


warm  air,  it  is  necessary  to  provide  a  suffi- 
ciency of  suitable  outlets.  The  system  is 
difficult  to  install  in  existing  buildings  owing 
to  the  size  of  ducts  compared  with  hot-water 
or  steam  pipes,  necessitating  much  cutting 
away.  The  advantages  claimed  for  the 


burns  and  dries  the  air.  The  stove  is  apt  to 
be  burnt  through  and  permit  sulphur  fumes 
and  probably  overheated  air  or  gases  to  enter 
the  ducts  and  set  fire  to  the  building.  It 
cannot  be  easily  installed  in  existing  buildings. 
In  every  case  air  should  be  drawn  from  an 


216 


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MUNICIPAL    AND   SANITARY  ENGINEERING. 


HOR 


unpolluted  source,  the  heating  chamber  and 
ducts  should  be  occasionally  cleansed,  and 
the  air  humidified  when  possible,  and  adequate 
exhaust  ventilation  provided. 

AIR  WARMING  STOVES. — These  stoves  are 
very  suitable  for  many  buildings,  and  are 
extensively  used  for  hospitals.  A  good  descrip- 
tion of  such  a  stove  is  that  manufactured  by 
Messrs.  Shorland.  The  "  Galton  "  air  warm- 
ing stove  is  also  well  known.  In  all  such 
heating  appliances  the  air  is  drawn  from 
outside  and  warmed  by  contact  with  the 
exterior  of  the  stove,  afterwards  passing  into 
the  room — the  cheerful  appearance  of  the  fire 
not  being  interfered  with. 

THE  "  BECK  "  RAPID  CIRCULATION  HOT 
WATER  APPARATUS. — This  simple  but  inge- 
nious apparatus  (Fig.  9)  is  primarily  based  on 
the  recognised  fact  that  ebullition,  or  the  pro- 
duction of  steam  bubbles  in  an  ascending  flow 
pipe  may  have  the  effect  of  causing  a  con- 
siderable acceleration  of  the  circulation, 
provided  that  suitable  means  are  employed  to 
regulate  the  ebullition,  which  unchecked 
causes  shocks  and  noise.  From  an  ordinary 
hot  water  boiler  an  ascending  main  flow-pipe 
is  taken  up  into  a  pocket  or  bottle,  from  the 
lower  part  of  which  the  circuit  pipes  are 
taken,  while  from  the  upper  part  a  pipe  is 
led  first  down  through  a  deep  siphon  and 
then  directly  up  to  the  expansion  tank.  In 
operation  the  steam  bubbles,  being  lighter 
than  the  water,  reach  the  upper  part  of  the 
pocket,  where  they  accumulate  in  quantity 
sufficient  to  cause  a  displacement  of  the  water  in 
the  siphon  towards  the  expansion  tank.  This 
displacement  is  taken  advantage  of  to  actuate 
a  diaphragm  or  other  form  of  regulator, 
which,  through  a  suitable  arrangement  of 
pulleys  and  chain,  acts  upon  the  ashpit  and 
smoke-pipe  dampers — checking  the  fire  and 
stopping  the  production  of  further  steam 
bubbles.  As  soon  as  the  temperature  by  this 
means  has  diminished,  the  steam  condenses, 
causing  a  reverse  displacement,  which, 
through  the  regulator,  acts  on  the  fire  to 
render  it  again  more  active.  The  effect  of 
the  arrangement  described  is  to  prevent  the 


steam  bubbles  passing  into  the  heating  cir- 
cuits at  all,  while  taking  advantage  of  their 
presence  to  cause  a  considerable  acceleration 
of  the  water  in  the  circuit  pipes,  and  the 
practical  result  on  the  hot  water  apparatus  is 
a  very  considerable  reduction  of  the  sizes  of 
all  the  circuit  pipes,  and  of  all  the  radiation. 
—(See  also  "  HOT-WATER  SUPPLY".)  W.  F. 

Hermetically  Sealed. — A  vessel,  tube,  or 
other  enclosure  is  said  to  be  "  hermetically 
sealed  "  when  it  is  closed  completely  against 
the  passage  of  air,  gas,  or  other  fluid 
by  fusing  the  extremity  or  opening  of  such 
vessel.  The  term  is  sometimes  less  correctly 
applied  to  any  air-tight  closure,  and  is  also 
commonly  used  in  connection  with  sanitary 
fittings,  traps,  pipe-joints,  &c.,  which  are  proof 
against  the  passage  of  sewer  gases. 

"  Hermite  Process  "  OF  SEWAGE  PURIFI- 
CATION. This  system  was  installed  for  the 
purpose  of  disinfecting  the  sewage  in  a  main 
line  of  intercepting  sewers  in  Ipswich  by  Messrs. 
Patterson  &  Cooper,  Engineers,  Westminster. 
A  deodorising  and  antiseptic  fluid  was  pro- 
duced by  electricity  from  sea  water,  or  from  a 
solution  of  magnesium  and  sodium  chlorides. 
This  fluid  was  put  into  the  drains  or  applied  to 
the  flushing  of  w.c.'s,  much  in  the  same  way 
as  in  "  Conder's  process"  (see  "  CONDER'S  SUL- 
PHATE OF  IRON  PROCESS").  In  Ipswich  the 
antiseptic  fluid  was  admitted  at  the  head  of 
the  main  sewer,  and  the  organic  constituents 
in  the  sewage  were  oxidised  thereby ;  but  the 
process  was  discontinued  about  the  year 
1905. 

Horse-Power. — The  indicated  horse-power 
of  an  engine  is  readily  calculated  from  the 
indicator  diagram  (see  "  INDICATOR  "),  and  for 
this  purpose  the  mean  effective  pressure  per 
square  inch  within  the  cylinder  must  be 
found.  This  is  done  in  practice  by  dividing 
the  diagram  into  ten  parts  by  equidistant 
vertical  lines,  then  scaling  off  the  pressures 
from  the  diagram  at  the  middle  of  each 
division  within  the  enclosed  curve,  and  finding 


217 


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ENCYCLOPEDIA  OF 


HOT 


the  average  by  dividing  the  aggregate  of  the 
pressures  so  scaled  by  ten.  Having  found  the 
mean  pressure  acting  on  the  piston  through- 
out its  stroke,  the  following  rule  may  then  be 
applied  to  find  the  horse-power,  viz. :  Multiply 
the  area  of  the  piston  in  square  inches  by  the 
mean  pressure  per  square  inch,  and  by  the 
piston  speed  in  feet  per  minute ;  then  divide 
the  product  by  33,000  ft.  Ibs.  per  minute  (the 
equivalent  of  one  horse-power  per  minute), 
and  the  quotient  is  the  required  indicated 
horse-power.  This  rule  is  usually  put  in  the 
form  of  a  formula,  thus : — 


Indicated  horse-power  = 


PLAN 


,  in  which 


33,000' 
P  =  the  mean  pressure  on  the  piston  in  Ibs. 

per  square  inch. 
L  =  length  of  stroke  in  feet. 
A  =  the  area  of  the  piston  in  square  inches. 
N  =  the  number  of  strokes  per  minute. 

The  "  brake,"  "actual,"  or  "  effective"  horse- 
power of  an  engine  is  the  measured  horse- 
power given  off  from  the  crank-shaft  of  the 
engine  ;  or,  may  be  described  as  the  net 
effective  horse-power  available  for  external 
work,  and  as  shown  by  the  friction  brake.  It 
is  the  "  indicated  horse-power  "  as  given  by  the 
above  scale,  less  the  power  required  to  drive 
the  engine  itself,  which  latter  may  vary  from 
10  to  25  per  cent,  according  to  the  type  and 
size  of  the  engine.  The  "mechanical  efficiency" 
of  an  engine  is  the  ratio  of  the  brake  to  the 
indicated  horse  -  power,  —  thus  mechanical 
efficiency  : — 

Brake  horse-power 
~  Indicated  horse-power* 

The  term  "nominal"  horse-power,  though 
gradually  becoming  obsolete,  is  still  used  in 
England  to  express  certain  proportions  of 
cylinder,  but  has  no  generally  recognised 
value  as  a  standard  of  measurement.  The  use 
of  the  term  is  now  largely  discarded  owing  to 
its  having  gradually  receded  so  far  below  the 
actual  horse-power,  but  it  is  found  convenient 
for  rating  purposes  to  have  a  rule  for  estimat- 
ing the  power  of  an  engine  from  its  general 
dimensions.  The  nominal  horse-power  may  be 


taken  at  about  one-sixth  the  indicated  horse- 
power. 

Hot  Water  Supply. — General  Systems- 
Tank  —  Cylinder  —  Combined  Systems  —  Boilers 
and  Incrustations — Steam  Calorifiers — Mixing 
Valves — Hot  Water  Calorifiers — Hot  Water  Gas 
Geysers — Gas  Boilers — Materials — Boiler  Explo- 
sions.— A  hot- water  supply  apparatus,  to  be  con- 
sidered satisfactory,  should  yield  an  adequate 
supply  of  hot  water  at  all  taps  within  a  short 
time  of  the  lighting  of  the  fire — say,  one  hour. 
In  addition,  the  fuel  consumption  should  be 
moderate  ;  provision  made  for  shutting  down 
and  emptying  the  apparatus  for  the  execution 
of  repairs,  cleaning  out  of  boiler,  &c.  ;  the 
heat  conserved  by  placing  .the  pipes  and 
storage  vessels  in  warm  positions,  or  by 
covering  the  same;  and  a  reliable  form  of 
safety  valve  should  be  fitted  to  the  boiler. 
Moreover,  the  size  of  the  boiler  and  pipes, 
together  with  the  storage  vessel,  should  be 
properly  proportioned.  As  it  is  seldom  neces- 
sary to  draw  water  off  continuously,  some 
means  of  storing  the  heated  water  is  usually 
provided ;  closed  storage  vessels  of  a  rect- 
angular (tank)  or  circular  (cylinder)  form 
being  mostly  used,  and  connected  to  the  boiler 
by  "  flow  "  and  "  return  "  pipes.  The  manner 
of  connecting  pipes  to  and  from  the  storage 
vessel,  and  the  position  occupied  by  the  latter 
varies,  constituting  what  are  known  as 
different  systems.  There  are,  however, 
certain  principles  and  essential  details 
common  to  all  systems : 

(a)  The  boiler  must  be  placed  below   the 
storage  vessel. 

(b)  Boiler   must   be  connected   to   storage 
vessel  by  two  pipes,  viz. : 

Flow  pipe,  the  lower  end  of  which  leaves  the 
top  of  boiler,  the  other  end  terminating  in  the 
vessel  about  one-third  the  height  of  same  from 
the  top. 

Eeturn  pipe.  The  lower  end  terminates 
near  bottom  of  boiler;  the  other  end  at  bottom 
of  storage  vessel. 

These  pipes  must  be  given  a  rise  towards 
the  storage  vessel  of  at  least  1  in.  in  10  ft. 


218 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


HOT 


(c)  The  cold  water  feed  is  connected  either  to 
the  return  pipe,  boiler,  or  to  the  bottom  of 
storage  vessel,  preferably  the  latter.  It  should 
be  of  ample  diameter  to  ensure  water  entering 
the  apparatus  as  fast  as  it  is  withdrawn,  and 
a  stopcock  of  the  fullway  type  fitted  thereon. 
The  pipe  should  be  connected  in  such  a  manner 
that  convection  currents  cannot  rise  and  set 
up    "local    circulation"  therein;    a    simple 
method  being  to  form  a  dip  before  the  same 
enters  the  apparatus.     It  is  a  good  plan  to 
place  a  tee-piece  or  other  fitting  on  the  end  of 
the  supply  pipe  in  storage  vessel  to  spread  the 
incoming   water  over   the   bottom    of   same, 
that  the  water   may   not    readily    push    its 
way  up    to    and    mingle    with    the    hottest 
water  at  top  of  storage  vessel ;  at  the  same 
time  the  incoming  water  is  prevented  from 
taking   a   direct  course   to  those  pipes  from 
which  water  is  being  drawn. 

(d)  An  open    pipe,  or,    as   it  is  generally 
termed,  "  expansion  or  exhaust  pipe,"  usually 
J   in.   to   1   in.    diameter,  is  taken    off    the 
top   of    storage    vessel,  whence  it  rises,  ter- 
minating a  short  distance  above  the  level  of 
water  in  supply  cistern.     This  pipe  permits 
air  to  automatically  pass  out  of  the  apparatus, 
and    also   prevents    a     "  swelling-back "     of 
water  (much  in  excess  of  the  actual  expansion) 
into  the  supply  cistern  ;  the  pipe  also  prevents, 
should  the  stopcock  on  supply  be  inadvertently 
closed,  the  apparatus  being  sealed  and  sub- 
jected to  increased  pressure.    The  end  may  be 
either  just  carried  above  and  turned  down  to 
discharge   into  supply  cistern,   or  may  pass 
through   a   roof.      The   former   is  the    most 
usual,  and  is  generally  satisfactory.     Should 
the  boiler,  however,  be  of  a  powerful  descrip- 
tion, an  ejection  of  steam  and  water  may  take 
place,  filling  the  roof  space  with  steam,  and 
also   heating    the  water    in   supply   cistern. 
Should  the  pipe  be  taken  through  the  roof, 
that    portion     containing    water     should,   if 
possible,  be  kept  inside  to  prevent  freezing ; 
failing  this  it  should  be  well  protected.      The 
term  "  expansion  pipe  "  is  hardly  a  good  one ; 
water  upon  being  heated  expands  about  -^s  of 
its  volume  from  40°  to  212°  F.,   or   boiling 


point;  the  increase  due  to  expansion  is 
gradually  pushed  through  the  supply  pipe  into 
the  supply  cistern,  the  capacity  of  which, 
measured  above  the  water  line  when  cold, 
should  therefore  be  at  least  equal  to  -^  the 
volume  of  water  contained  in  the  whole 
apparatus. 

(e)  Arrangement  for  Emptying  :  An  empty- 
ing cock,  with  a  loose  key,  to  be  used  only  in 


FIG.  1. — High  Pressure  System. 


the 


case    of  repairs — should  be  provided   at 
lowest  part  of  the  apparatus. 

(/)  Safety  Valve:  A  good  form  of  safety 
valve — preferably  of  the  dead-weight  type- 
should  be  connected  direct  to  the  boiler,  and 
be  periodically  tested  by  lifting  the  spindle 
to  ensure  the  valve  is  not  stuck  fast  or 
choked. 

(g)  Draw-off    Connections  :       Hot     water 


219 


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ENCYCLOPEDIA  OF 


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should — especially  in  the  case  of  lavatory 
basins — be  obtained  immediately  the  tap  is 
opened.  As  water  will  not  circulate  in  single 
branch  pipes,  the  length  should  be  reduced 
as  much  as  possible,  either  by  carrying  the 
main  pipes  in  the  direction  of  the  fittings  to 
be  supplied,  or  by  running  branch  circuits. 
The  connection  of  branch  circuits  to  main 
pipes  and  storage  vessels  is  important,  and 
it  is  as  well  to  point  out,  that  when  a  tap 


FIG.  2.— Tank  System. 

is  opened  on  any  pipe,  water  rushes  to 
such  tap  from  every  possible  source,  hence, 
from  the  two  ends  of  circuit  branches ;  these 
branches  should,  therefore,  terminate  only 
where  the^hottest  water  is  available. 

SYSTEMS. — TANK  SYSTEMS. — A  tank — usually 
rectangular — is  placed  above  the  highest  draw- 
off  tap  and  connected  to  the  boiler  by  flow  and 
return  pipes ;  an  open  pipe  is  taken  off  top 
of  tank  and  the  cold  water  supply  brought 
in  at  bottom  of  same,  all  as  heretofore 
detailed.  Draw-off  connections  are  taken 


from  the  flow  pipe,  or  from  a  specially 
provided  pipe  connected  to  the  tank  at 
about  the  same  level  as  the  end  of  flow 
pipe  therein.  Connections  are  sometimes 
taken  off  the  expansion  pipe,  which  is  a 
satisfactory  arrangement,  providing  an  out- 
flow of  water  can  be  maintained ;  this,  of 
course,  depends  upon  the  rate  at  which  cold 
water  enters  the  apparatus.  Objections 
sometimes  urged  against  the  "  tank  system  " 
are :  (a)  The  placing  of  the  storage  vessel  at 
some  distance  from  boiler  necessitates  long 
flow  and  return  pipes  with  consequent  friction 
and  loss  of  heat  from  the  surfaces  thereof. 

(b)  The  tank  is  frequently  placed  in  a  cold 
position. 

(c)  When  draw-off  connections   are   taken 
from  the  main   flow  pipe,  the  tank  may  be 
emptied  during  failure  of  the  water  supply ; 
the  water  in  boiler  may  then  evaporate  and  the 
boiler  be  burned  and  leak.     An  advantage  of 
the  tank  system  is  that  the  placing  of  storage 
vessel  above  the  taps  ensures  a  good  outflow 
of  water    to    the    highest    taps,    the    water 
gravitating  thereto  until  the  water  in  tank   is 
lowered  to  the   level   of   the   particular  pipe 
supplying  the  tap.     Should  the  draw-off  tap, 
however,  be  on  the  main  flow  pipe,  water  will 
afterwards    pass   to   the   tap  via  the   return 
pipe,   being,  of   course,  much  colder.     From 
what  has  already  been  stated  with  reference 
to  "  draw-off  connections  "  a  tap  placed  on 
the    flow-pipe    must   always   result    in    the 
issuing  water  being  drawn  from  both  the  flow 
and  return,   although,  owing  to  the  force  of 
gravitation  and  generally  lesser  friction,  the 
bulk  would  be  from  the  flow  pipe  so  long  as 
the    upper     end    is   immersed ;    hence,    the 
arrangement  is  generally  satisfactory. 

CYLINDER  SYSTEM.  —  A  storage  vessel— 
generally  of  cylindrical  form  to  withstand  the 
greater  hydraulic  pressure — is  placed  near  to 
and  just  above  the  level  of  boiler,  short  flow 
and  return  pipes  only  being  required.  The 
open  or  expansion  pipe  is  taken  off  top  of 
cylinder  and  should  travel  in  the  direction  of 
draw-off  taps,  which  are  then  connected 
thereto,  the  pipe  ultimately  terminating  above 


220 


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MUNICIPAL  AND   SANITAEY  ENGINEEEING. 


HOT 


the  supply  cistern  as  previously  explained. 
To  ensure  the  issue  of  the  hottest  water 
immediately  a  tap  is  opened,  the  water  should 
circulate  past  the  various  taps,  which  may  be 
done  by  returning  the  expansion  pipe — after 
the  last  branch  is  passed — to  the  cylinder, 
connecting  to  the  same  about  6  in.  from  top, 
thus  ensuring  the  hottest  water  only  reaching 
the  taps.  The  foregoing  would  be  termed  a 
"  secondary  circulation." 
The  cold  water  supply  is  connected  to  the 


FIG.  3.— Cylinder  System. 

bottom  of  cylinder  and  should  be  capable  of 
ensuring  a  continuous  flow  of  water  at  the 
taps.  An  emptying  cock  is  also  imperative. 

The   advantages  claimed   for   the  cylinder 
system  are : 

(a)  Short   flow  and  return   pipes   between 
boiler  and  storage  vessel,  ensuring  a  quicker 
transference   of  heated    water   and  reducing 
risk  of  freezing. 

(b)  As  draw-off  connections  spring  from  the 
top  of   storage   vessel   the   latter   cannot   be 


thereby  emptied  should  the  water  supply 
fail. 

(c)  Cylinder  is  generally  placed  in  a  warmer 
position. 

A  fault  often  met  with  is  a  poor  out- 
flow of  water  to  fittings  placed  just  under 
the  cold-water  cistern,  this  being  due  in  the 
first  place  to  the  low  head  of  water,  and 
secondly,  to  the  water  having  to  travel  down 
to  the  cylinder  and  thence  push,  as  it  were, 
the  hot  water  before  it  until  the  top  is  reached ; 


FIG.  4  .-^-Cylinder  System  with  Secondary 
Circulation. 

hence  in  this  respect  the  tank  system 
possesses  an  advantage. 

COMBINED  SYSTEMS. — A  combination  of  the 
foregoing  systems  has  the  advantages  of  both 
and  the  disadvantages  of  neither. 

This  may  be  described  as  a  cylinder  system 
with  secondary  circulation,  supplemented  by 
a  tank  placed  above  the  highest  draw-off  tap 
and  connected  to  the  cylinder  system  by  dis- 
connecting the  highest  part  of  the  secondary 


221 


HOT 


ENCYCLOPAEDIA  OF 


HOT 


circulation  and  carrying  the  same  up  to 
and  connecting  to  the  bottom  of  tank,  an 
open  pipe  being  taken  from  top  of  tank. 
Draw-off  connections  may  be  taken  from 
either  the  secondary  flow  or  return ; 
other  return  pipes  may  be  taken  from  the 
bottom  of  tank  to  supply  taps,  and  should  be 
ultimately  connected  to  cylinder  near  the  top. 
The  secondary  flow  pipe  may  stand  up  a  short 


fire  being  made  to  suffice  for  cooking,  hot 
water  supply,  and  for  warming  the  kitchen. 
More  fuel,  however,  is  required  for  cooking, 
&c.,  owing  to  a  large  quantity  of  heat  being 
absorbed  by  the  hot  water  apparatus ;  a  further 
quantity  is  also  lost  by  passing  or  escaping 
up  the  chimney,  although  this  may  be  reduced 
by  fixing  a  suitable  but,  at  the  same  time, 
more  expensive  type  of  boiler.  The  efficiency 


FlG.  5. — Combined  System. 


distance  inside  the  tank,  but  a  return  pipe 
must  leave  the  bottom  to  ensure  through 
circulation.  The  combined  capacity  of  the 
two  storage  vessels  is  not  increased  beyond 
that  of  other  systems,  and  it  is  desirable 
to  make  the  upper  vessel  about  two-fifths  of 
the  required  storage. 

BOILERS.  —  The  most  usual  medium  of 
obtaining  a  supply  of  hot  water  is  by  a  boiler 
placed  at  the  back  of  the  kitchen  range,  one 


of  range  boilers  is  proportional  to  the  area 
presented  to  the  fire  ;  for  this  reason  "  boot 
boilers"  yield  larger  quantities  of  hot  water 
by  absorbing  more  flue  heat  than  ordinary 
"  bath  boilers."  The  proportioning  of  boilers 
and  storage  vessels  is  very  important,  and 
although  no  hard  and  fast  rule  can  be  laid 
down,  it  is  generally  preferable  to  use  small 
rather  than  large  storage  vessels,  quicker 
results  being  obtainable.  For  ordinary 


222 


HOT 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


HOT 


work    the   following    proportions    are    satis-         STEAM  CALORIFIERS  OR  HEATERS. — Where  a 


factory : — 


Width  of 
Boiler. 

Shape. 

Storage 
Vessel. 

Flow  and 
Return. 

Number  of 
Taps. 

Inches. 
9 

Saddle 

Gallons. 

25 

Inches. 
1 

2  or  3 

9 

Boot 

30 

1 

3  or4 

11 

Saddle 

30 

1 

,, 

11 

Boot 

40 

1| 

4  or  5 

12 

Saddle 

35 

M 

12 

Boot 

45 

t) 

,, 

14 

Saddle 

40 

t 

14 

Boot 

50 

" 

5  or  6 

INDEPENDENT  BOILERS.— The  most  economi- 
cal arrangement  for  heating  water  is  by 
means  of  independent  boilers.  These  boilers 
are  circular  in  form  and  connected  in  a 
similar  manner  to  range  boilers.  The  fire 
may  be  banked  to  last  several  hours,  and 
practically  any  fuel  may  be  burned  therein. 
They  are  eminently  suited  for  large  houses, 
hotels  and  the  like,  in  fact,  wherever  hot 
water  in  fairly  large  quantities  is  required  at 
all  times  of  the  day. 

BOILERS  AND  INCRUSTATION. — Water  con- 
taining lime  in  solution  (temporary  hard 
water)  is  apt  to  cause  much  trouble  and 
expense  by  furring  of  the  boiler  and  pipes. 
Heating  such  water  to  a  temperature 
approaching  boiling  point  removes  the  tem- 
porary hardness  by  expelling  carbonic  acid 
from  the  soluble  calcic  bicarbonate,  and 
causing  precipitation  of  the  insoluble  calcic 
carbonate,  producing  fur,  which,  unless 
removed  from  time  to  time,  prevents  the 
passage  of  heat  to  the  water  within  the  boiler, 
eventually  causing  destruction  of  the  same  by 
burning  of  the  plates.  The  extent  of  fur 
formation  depends  upon :  (a)  the  amount  of 
lime  in  solution ;  (b)  the  quantity  of  fresh 
water  passed  through  the  boiler ;  and  (c)  the 
temperature  of  the  latter ;  a  variation  in  any 
one  of  which  will  bring  about  different  results. 
All  boilers  used  for  temporary  hard  water 
should  be  provided  with  means  of  access  and 
of  a  form  to  enable  the  interior  to  be  freed 
from  fur ;  hence,  coil  boilers  and  the  like  are 
quite  unsuited  for  such  purposes. 


steam  supply  is  available  the  same  may  be 
usefully  employed  in  warming  water  for 
domestic  or  supply  purposes.  These  calori- 
fiers  may  be  powerful  enough  to  heat  the 
water  as  it  passes  through,  or  where  the 
demand  is  large  and  intermittent  a  storage 
vessel  may  be  coupled  up  to  the  same  or  a 
storage  form  of  calorifier  used  instead.  The 
connections  to  calorifiers  and  storage  vessels, 


FIG.  6. — High  Pressure  Boiler  and  Coil  for 
Indirect  Supply. 

and  the  arrangement  of  cold  supply,  expan- 
sion pipe,  &c.,  is  similar  to  the  ordinary  hot 
water  apparatus.  The  efficiency  of  calorifiers, 
depends  upon  their  form,  the  arrangement  of 
tubes  within,  and  the  steam  pressure.  An 
automatic  steam  control  valve  to  govern  the 
temperature  of  water  and  prevent  waste  of 
steam  is  a  desirable  feature.  A  very  efficient 
form  of  tube  for  use  in  calorifiers  is  an 
indented  type  (Eow's  patent)  as  may  be  seen 
from  the  following.  "  Eelative  heating  value 


223 


HOT 


ENCYCLOPAEDIA  OF 


HOT 


of   1    sq.   ft.   of  indented  heating   surface  at 
various  steam  pressures  (Bow) "  : — 

Steam  in  Ibs.  per  sq.  in.       5    10    15    20    25    30      40 
Gallons  of  water  raised 

from    50°  to  180°  F. 

in  1  hour        . .          ..     35    42    56    62    80    93    103 

An  allowance  should  be  made  for  scaling 
up  when  hard  water  is  used. 

XTixiNG  VALVES.  —  Water  is  sometimes 
heated  by  the  intermixing  of  steam  and  water 


FIG.  7.— Section  of  Twin  Boiler 
(Jones  &  Attwood's  Patent). 

in  a  valve  as  the  water  issues.  These  valves 
may  be  regulated  to  give  water  at  any  pre- 
determined temperature.  An  objection  some- 
times urged  against  this  arrangement  is  that 
a  failure  of  the  steam  supply  would  enable 
steam  to  issue  should  the  valve  be  opened. 
They  certainly  offer  a  convenient  and  cheap 
means  of  obtaining  hot  water,  but  where  taps 
are  scattered  it  would  probably  be  more 
economical  to  use  calorifiers.  The  use  of  live 


steam  also  entails  the  addition  of  fresh  water 
to  the  boiler. 

HOT  WATER  CALORIFIERS. — Where  water 
contains  much  lime  in  solution  it  may  be 
preferable  to  heat  the  same  by  "  indirect 
methods,"  i.e.,  by  means  of  a  boiler  connected 
to  a  coil  or  closed  vessel  placed  inside  a 
storage  vessel,  the  water  therein  being  heated 
by  contact  with  the  coil  or  closed  vessel.  The 
advantage  of  such  an  arrangement  is  that 
incrustation  is  avoided  as  the  water  in  the 
boiler  and  coil,  &c.,  is  unchanged,  whilst  the 
water  in  the  storage  vessel  is  not  heated  to  a 
temperature  high  enough  to  expel  carbonic 
acid  and  cause  fur  formation.  The  primary 
heating  apparatus  may  consist  of  an  ordinary 
independent  boiler  with  a  coil  or  other 
arrangement  connected  thereto,  or  may  be  of 
a  "  high  pressure "  description.  Obviously 
more  heating  surface  will  be  required  in  the 
storage  vessel  than  in  the  boiler ;  the  surface 
of  coil  or  heater  in  the  vessel  should  be  about 
five  times  the  heating  surface  allowed  in  the 
boiler. 

HOT  WATER  GAS  GEYSERS. — Hot  water 
geysers  are  extensively  used  for  supplying  hot 
water  for  baths  and  lavatories,  especially  in 
flats,  bungalows,  and  houses  not  possessing  a 
hot  water  apparatus  ;  they  are  also  frequently 
fixed  where  a  warm  bath  is  required  at  an 
early  hour.  Geysers  are  generally  constructed 
of  copper — tinned  inside — and  possess  a  large 
heating  surface  over  which  the  water  flows,  a 
continuous  supply  being  furnished  so  long  as 
gas  is  burning.  The  temperature  of  the 
issuing  water  will  depend  upon  the  rate  at 
which  the  same  passes  through  the  geyser, 
the  gas  consumption  remaining  the  same. 
In  a  good  type  of  geyser,  the  gas  should  not 
have  access  to  the  water ;  an  automatic  valve 
to  ensure  that  gas  can  only  be  burned  whilst 
water  is  in  or  passing  through  the  same 
should  be  fitted,  and  a  flue  pipe,  not  subject 
to  "  blow-down  "  provided  ;  in  fact,  no  geyser 
should  be  fitted  without  such  a  flue.  A  warm 
bath  should,  with  gas  at  3s.  per  1,000  cu.  ft., 
be  obtained  for  about  Id. 

GAS   BOILERS.— Gas  boilers  are   frequently 


224 


HOT 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


HOT 


used  in  place  of  and  also  to  supplement 
range  boilers.  They  are  useful  where  a 
continuous  supply  is  not  required.  When 
used  to  supplement  an  existing  system  the 
boiler  is  connected  to  the  flow  and  return 
thereof  by  branch  pipes.  A  flue  is  re- 
quired with  these  boilers ;  a  thermostatic 
valve  to  automatically  lower  the 
gas  when  the  water  has  reached  a 
predetermined  temperature  is  a  useful 
accessory. 

MATERIALS. — For  temporary  hard 
water,  wrought  iron  galvanized  is  the 
most  suitable  material  for  pipes  and 
storage  vessels,  the  boiler  being 
usually  uncoated.  Owing  to  the 
action  of  most  soft  waters  on  un- 
coated iron  causing  discoloration, 
or  in  the  case  of  galvanized  pipes, 
&c.,  dissolving  the  zinc  coating,  cop- 
per is  to  be  preferred.  The  tubes 
should  be  thick  enough  for  screwing 
and  gun-metal  fittings  used  through- 
out. It  is  often  advisable  to  tin  the 
threads  and  afterwards  sweat  the 
joints  together.  Copper  pipes  may 
be  easily  bent  in  the  ordinary 
manner,  unless  sharp  bends  are 
required  or  the  pipe  is  of  a  large 
diameter,  when  it  may  be  filled  \vith 
sand,  resin  or  lead  to  prevent  flatten- 
ing. Pipe  clips  should  be  used  and 
built  into  the  wall  to  support  and 
permit  movement  of  the  pipes ;  where 
passing  through  walls,  floors,  &c., 
metal  sleeve  pieces  should  be  pro- 
vided. 

BOILER  EXPLOSIONS. — Although  the  ordinary 
domestic  boiler  is  of  small  dimensions,  an 
explosion  may  be  wrought  with  serious,  if 
not  fatal,  consequences.  The  cause  of  domestic 
boiler  explosions  is  frequently  misunderstood. 
It  may  be  stated  that  these  explosions  are 
invariably  caused  by  a  stoppage  of  the  cir- 
culation pipes,  and  not  through  the  entry  of 
water  into  an  empty  red-hot  boiler.  A  com- 
plete stoppage  of  the  circulation  pipes  her- 
metically seals  the  water  in  the  boiler;  upon  the 


application  of  heat  the  temperature  is  raised, 
and  expansion  of  the  contained  water  being 
prevented,  an  enormous  pressure  is  created, 
which  ultimately  bursts  the  boiler.  As  an 
example  of  the  enormous  stored  energy  under 
these  circumstances,  1  cu.  ft.  of  water  heated  to 
exert  60  Ibs.  pressure  'per  square  inch  amounts 


FIG.  8.— Hot  Water  Calorifier  for  Indirect  Hot  Water  Supply. 


to  about  300,000  foot  pounds,  or  350  times 
as  much  as  an  equal  volume  of  steam  at  the 
same  temperature.  By  far  the  largest  number 
of  explosions  are  due  to  pipes  being  choked 
with  ice ;  it  is  seldom  that  an  explosion  is 
due  to  fur  owing  to  the  accumulation  being 
gradual,  and  when  nearly  stopped  a  loud 
thumping  noise  gives  ample  warning.  It  will 
be  at  once  obvious  that  the  placing  of  stop- 
cocks on  flow  and  return  pipes,  especially  in 
the  absence  of  a  safety-valve,  is  a  dangerous 


M.S.E. 


225 


HOT 


ENCYCLOPEDIA   OF 


HOW 


proceeding.  It  is  popularly  supposed  that 
the  entry  of  water  into  a  red-hot  boiler  will 
burst  the  same,  and  is,  in  fact,  the  cause  of 


FIG.  9. — Horizontal  Steam  Water  or  Calorifier 
(Storage  Pattern). 

explosion.  In  the  first  place,  some  time  would 
elapse  before  the  whole  of  the  water  in  the  boiler 
was  evaporated  and  further,  should  the  water 


FIG.  10. — Steam  Heater  with  Coil. 

suddenly  enter  a  red-hot  boiler,  the  steam 
generated  would  force  the  water  back  until  the 
steam  pressure  was  released. 
It  is  possible  that  the  boiler 
may  be  fractured,  but  nothing 
in  the  nature  of  a  serious  ex- 
plosion would  result.  Very 
few  people  would,  the  writer 
believes,  keep  a  fire  in  a  range 
fitted  with  a  boiler  when  no 
water  was  obtainable  at  the 
taps ;  in  fact,  the  absence  of 
water  is  usually  taken  as  an 
indication  that  something  is 
wrong.  With  circulation 
pipes  choked  with  ice,  however, 


no  such  warning  is  given;  hence  the  import- 
ance of  placing  the  pipes  in  warm  positions 
or  keeping  the  water  warm.  The  writer 
knows  of  no  instance  where  a  domestic  boiler 
explosion  has  occurred  when  a  safety  valve 
has  been  fitted  direct  to  the  boiler. 

There  are  several  other  proprietary  systems 
of  "accelerated  hot-water  circulation."  The 
advantages  claimed  for  such  systems  are  that 
smaller  pipes  may  be  used  and  the  pipes  run 
at  any  desired  level ;  in  many  cases  the  boiler 
may  be  placed  above  the  lowest  radiators, 
an  obvious  advantage  in  many  instances. 
Amongst  such  systems  in  successful  operation 
may  be  mentioned  "  The  Pulsial  system  of 
heating  by  low  pressure  hot  water,"  erected 
by  Messrs.  Werner,  Pfleiderer  &  Perkins,  Ltd., 
Kingsway,  London,  W.C. ;  "  Barker's  Cable 
system  of  vacuum  hot-water  heating,"  erected 
by  J.  F.  Phillips  &  Son,  Old  Queen  St.,  West- 
minster ;  "The  Reck  system,"  designed  by 
Captain  Reck,  of  Copenhagen.  In  the  fore- 
going systems,  steam  at,  or  about,  atmo- 
spheric pressure  is  generated  in  the  boiler. 
Another  system  is  to  install  a  motor  or  steam- 
driven  pump  on  the  circulation  pipes  near  the 
boiler,  hot  water  being  pumped  through  the 
apparatus.  W.  F. 

House  Refuse. — (See  "  REFUSE  DISPOSAL.") 

"Howatson  Process"  OF  SEWAGE  PURI- 
FICATION.— This  system  has  been  tried  at 


STEAM   SUPPLY. 


CONDENSE    MAIN 


FIG.  11. — Arrangement  of  Steam  Calorifiers  for  Warming  of 
Hot  Water  Supply. 


226 


HYD 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


HYD 


Middelkerke,  "Wenduyne,  Haeren,  and  else- 
where. It  has  also  been  satisfactorily  applied 
to  the  purification  of  drinking  water  at  Ostend, 
Haeren,  and  other  places.  Peroxide  of 
chlorine  is  used  as  a  sterilising  agent,  and  this 
is  obtained  by  the  decomposition  of  chlorate 
of  potash  by  sulphuric  acid.  The  organic 
matter  in  the  sewage  is  rapidly  oxidised  by 
the  soluble  gas  thus  produced,  and  a  high 
degree  of  purification  is  obtainable. 


Hydraulic   Gradient. — (S 

PIPES  AND  CONDUITS.") 


ee 


"  FLOW    IN 


Hydraulic  Mean  Depth. — (See  "  FLOW 
IN  PIPES  AND  CONDUITS.") 

Hydrolytic  Tank.— The  first  tank  of 
this  type  was  installed  at  Hampton-on- 
Thames  in  1903.  The  novel  design  and  the 
special  mode  of  operation  implied  so  complete  a 
departure  from  the  usual  methods  of  construc- 
tion and  of  practice  that  more  than  ordinary 
thought  and  time  were  devoted  to  its  con- 
sideration. The  principles  of  its  action  are  as 
follows : — 

(1)  The  rapid  separation  of  the  main  volume 
(80  to  90  %)  of  the  liquid  from  the  remaining 
part  of  the  sewage. 

(2)  The  exclusion  of  this  proportion  from 
any  contact  with  the  resulting  sludge,  from 
the   presence   of    the   generated   gases,    and 
from  any  but  the  shortest  tank  operation. 

(3)  The   concentration   of    the    suspended 
impurities  in  the  smaller  volume  (10  to  20  %) 
of  the  sewage. 

(4)  The  continuous  removal  of  this  volume 
from  the  sedimentation  chambers  by  its  down- 
ward displacement  into  a  separate  chamber, 
where  the  suspended  matters  are  deposited. 

(5)  The  correction  of  the  periodical  outflow 
of  suspended  matter,  the  result  of  the  gaseous 
disturbances,  by  the  re-deposition  and  removal 
of  these  solids  in  an  additional  chamber. 

(6)  The  limitation  of  the  hostile  forces  of 
sedimentation  and  gaseous  eruptions  to  separate 
chambers. 

(7)  The   submission   of   the   whole  of   the 


227 


sewage  to  the  attracting  influence  of  self- 
cleansing  surfaces,  in  order  to  abstract  as 
large  a  proportion  of  the  finer  suspended  and 
colloidal  solids  as  possible. 

(8)  The  prevention  of  any  undue  accumula- 
tion of  scum  and  of  sludge  by  periodically 
withdrawing  the  excess  ;  and 

(9)  The    continued    maintenance    of     the 
working  capacities  of  the  several  chambers. 

The   following    description,    together   with 
the   drawings   of    the    Hampton    tank,    will 
demonstrate  how  these  principles  are  carried 
out.     The  sewage  having   passed  through  a 
J  in.  mesh  screen  enters  one  of  two  detritus 
tanks.      These    have    a    capacity    of    3,000 
gallons  each,  or  one-eightieth  of  the  present 
daily  flow  of  sewage,  and  are  worked  alter- 
nately, the  sewage  being  diverted  from  one 
to  the  other  every  fortnight.     The  sludge  is 
removed  from  the  full  tank  by  means  of  a 
valved  opening,  through  which  it  passes  to 
the  sludge  manhole.     In  this  way  nearly  one- 
half  of  the  total  quantity  of  sludge  is  removed 
from  the   sewage.     The  sewage   leaving   the 
detritus  tank  enters  the  centre  of  a  transverse 
channel,  which  conveys  it  into  the  sedimenta- 
tion  chambers    of    the    hydrolytic    tank   by 
delivering  it  behind  submerged  walls.     The 
tank  is  divided  by  light  walls  into  three  com- 
partments, the  centre  one  of   which   is   the 
reduction  chamber,  the  outer  two  being  the 
sedimentation  chambers.      The  only   means 
of  liquid  communication  between  these  com- 
partments  are  the  narrow   openings   at   the 
bottom  of  the  sedimentation  chambers.     At 
the  end  of  the  tank  is  a  weir  divided  into 
three   portions,  one  for  each  chamber ;   the 
relative  widths  of  these  divisions  govern  the 
outflow  of  sewage  from  the  several  chambers 
and  determine  the  proportional  quantity  which 
flows  through    each.     The   side   weirs  (sedi- 
mentation) have  a  width  of  7  ft.  each,  or  a 
combined   width   of   14   ft.,  and  the  central 
(reduction)  weir  has  a  width  of  2  ft.     The 
total  width  of  16  ft.  is,  therefore,  apportioned 
so   as   to   permit   of    87'5  %   of    the   sewage 
passing   along   the    sedimentation    chambers 
and   over   their   weirs,  whilst   ensuring  that 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


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12'5  %  of  that  liquid  shall  pass  out  of  the 
bottoms  of  them  into  the  reduction  chamber 
and  over  its  weir.  The  entire  volume  of 
sewage  enters  the  sedimentation  chambers. 
Of  this  volume  87'5  %  travels  along  a  prac- 
tically level  plane,  while  the  lighter  and 
heavier  particles  describe  upward  and  down- 
ward curves,  the  length  -  of  the  curve  being 
proportioned  to  the  weight  of  the  particle  and 
to  the  velocity  of  the  flow.  The  lighter  par- 
ticles rise  to  the  surface,  and  are  retained 
there  by  the  submerged  walls  at  the  end  of 
the  chamber.  The  heavier  particles  in  falling 
have  their  curve  shortened  by  the  descending 
volume  (1'2'5  %)  of  the  liquid  which  passes 
out  of  the  bottom  of  the  sedimentation  cham- 
bers into  the  reduction  chamber ;  in  other 
words,  the  natural  downward  displacement 
of  the  particles  are  accelerated  by  tha  down- 
ward flow  of  one-eighth  of  the  entire  volume 
of  sewage,  by  which  means  the  deposit  is 
carried  into  the  reduction  chamber.  The 
slower  rate  of  flow  in  this  chamber  permits 
the  solids  to  descend  into  the  lower  part  of 
the  chamber,  and  prevents  so  large  a  quantity 
of  the  deposited  matters  from  being  carried 
out  of  the  tank  during  periods  of  agitation 
caused  by  the  gases  generated.  The  forma- 
tion of  gases  is,  with  almost  negligible  excep- 
tions, limited  to  the  reduction  chamber.  The 
rising  gases  in  the  reduction  chamber  are 
separated  by  the  sloping  walls  from  the 
depositing  solids  in  the  sedimentation  cham- 
bers, and  thus  the  confusion  in  operation 
which  would  otherwise  ensue  is  obviated. 
The  part  of  the  chamber  below  the  openings 
at  the  bottom  of  the  sedimentary  chambers 
is  for  the  reception  of  sludge ;  it  is  designed 
to  hold  the  sludge  contained  in  40  days' 
average  flow  of  sewage.  In  actual  work, 
however,  it  holds  double  this  quantity.  Along 
the  floor  at  intervals  valves  are  fixed,  through 
which  3,000  gallons  of  sludge  are  removed 
from  the  tank  about  once  a  fortnight  into 
the  sludge  manhole.  Floating  solids  on  the 
surface  of  the  liquid  in  the  sedimentary 
chambers,  and  those  floated  in  the  reduction 
chamber,  are  occasionally,  when  unduly 


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detritus  tank.  The  sewage  flowing  over  the 
weirs  enters  a  channel  which  leads  to  the 
four  hydrolysing  chambers,  which  are  arranged 


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bottom  of  each  chamber  and  passes  upwards 
through  the  material  to  the  surface,  where 
it  flows  over  a  weir  and  descends  to  the  lower 
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229 


HYD 


ENCYCLOPAEDIA   OF 


HYD 


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230 


HYD 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


HYD 


lias  been  repeated  in  the  four  chambers  the 
liquid  enters  the  channel  which  conducts  it 
to  the  contact  beds.  Tank  and  channels  are 
mechanically  ventilated,  and  the  withdrawn 
gases  are  purified  before  being  discharged 
into  the  atmosphere.  The  sludge  is  conveyed 
into  trenches  in  the  land  and  is  almost  imme- 
diately covered  over  with  earth.  Five  years' 
uninterrupted  experience  has  demonstrated 
the  practical  value  of  the  hydrolytic  tank  as 
a  highly  efficient  means  of  removing  the  sus- 
pended matters  from  sewage,  for  collecting 
the  sludge,  and  for  admitting  of  the  maximum 
withdrawal  of  these  matters  during  the  con- 
tinuous work  of  the  tank. 

S.  H.  C. 

Hydraulic  Memoranda. — The  following 
brief  hydraulic  notes  and  memoranda  will  be 
found  convenient  for  reference  by  readers  of 
this  work  and  for  engineering  calculations 
generally : — 

WATEK,  EQUIVALENTS,  &c. 

One  Imperial  gallon  =  277*463  cu.  in. 
,,  ,,  ,,      =        '16  cu.  ft. 

,,  ,,  ,,       =    10*00  Ibs.  avoirdupois 

at  62°  F. 

,,  ,,  „       =      4*546  litres. 

One  United  States  gallon  =  231  cu.  in. 

„      —  8-33111  Ibs. 
One  cubic  foot  of  water     =  6*23    imperial 

gallons. 

=    7-480519  United 
States  gallons. 
=  62-28  Ibs. 
=      -55606  cwt. 
=      -0278  ton. 
=  28-3116  litres. 

,,  ,,  ,,         =      '0283  cu.  metre. 

One  cubic  inch  of  water  =  252*286  grains. 

„      =        -03604  Ib. 
One  pound  of  water  =      '10  Imperial  gallon. 

„     =  27-74  cu.  in. 

One  ton  of  water  =  224  Imperial  gallons. 
One  litre  of  water  =  '22  Imperial  gallon. 
One  cubic  metre  of  water  =  220     Imperial 

gallons, 


One  cubic  metre  of  water  =  1  ton  (approxi- 
mately) . 
One  kilo,  of  water  =  2-2046  Ibs. 

PRESSURE,  HEAD,  &c. 

Head  in  feet  X      "4335  =  pressure  in  Ibs.  per 

square  inch. 
Head  in  feet  X       '341    =  pressure  in  Ibs.  per 

circular  inch. 
Head  in  feet  X  62*425    =  pressure  in  Ibs.  per 

square  foot. 
Pressure  in  Ibs.  per  square  inch  X  2*306  =  Head 

in  feet. 
Pressure  in  Ibs.  per  square  foot  X  '016  =  Head 

in  feet. 
A  pressure  of  1  Ib.  per  square  inch  =  column 

of  water  2*31219  ft.  high. 
A  column  of  water  1  ft.  high  =  a  pressure  of 
"4325  Ibs.  per  square  inch. 

PIPES,  DISCHARGE,  &c. 

Gallons  contained  per  foot  run  of  pipe  =  (dia- 
meter in  inches)  2  X  "03~4. 

Lbs.  per  foot  run  of  pipe  =  (diameter  in 
inches)  3  X  *34. 

Doubling  the  diameter  of  a  pipe  increases  its 
capacity  four  times. 

Discharge  varies  as  the  square  root  •  of  the 
"  head." 

Cubic  feet  of  water  per  minute  X  9,000  = 
gallons  per  24  hours. 

The  friction  of  liquids  in  pipes  increases  as  the 
square  of  the  velocity. 

RAINFALL. 

Average  rainfall  for  England  is  usually  taken 

at  30  in.  per  annum. 
One  inch  of  rain  over  100  sq.  ft.  of  surface 

yields  52  gallons. 
One  inch  of  rain  over  an  acre  of  surface  = 

100  tons  of  water  (approximately). 
One  inch  of  rain  over  an  acre  of  surface  = 

3,630  cu.  ft.  of  water. 
One  inch  of  rain  over  an  acre  of  surface  = 

22,650  gallons. 
Rainfall  in  inches  X  '52  =  gallons  per  squar 

foot. 


231 


HYD 


ENCYCLOPAEDIA   OF 


HYD 


Eainfall  in  inches  X  2,323,200  =  cubic    feet 

per  square  mile. 
Eainfall  in  inches  X  14^  =  millions  of  gallons 

per  square  mile. 

EVAPORATION.  —  The  annual  amount  of  evapo- 
ration is  very  variable  according  to  circum- 
stances. On  land  surfaces  in  this  country  it 
varies  from  8  in.  to  20  in.  On  large  water 
surfaces  at  Lea  Bridge  it  was  found  to  be 
about  21  in.  per  annum,  but,  in  many  cases, 
the  amount  of  evaporation  from  large  water 
areas  is  equal  to  the  rainfall. 

HORSE-POWER.  —  The  horse-power  required  to 
raise  a  given  quantity  of  water  in  gallons  to 
a  given  height  is  found  as  follows  :  —  Multiply 
the  water  to  be  raised  in  gallons  per  minute 
by  10  and  by  the  height  the  water  has  to  be 
raised  in  feet,  and  divide  the  product  by  33,000. 
To  the  net  horse-power  thus  obtained  must 
be  added  an  allowance  to  cover  friction  and 
"  slip,"  according  to  the  necessities  of  the 
case.  An  addition  of  at  least  one-third  is 
usually  made. 

Another  rule  is  as  follows  :  — 
Actual  horse-power  =  '0023  H  Q. 
Where    Q  =  quantity    of    water    raised    per 

minute  in  cubic  feet. 
Where  II  =  height  in  feet. 

Contents  of  wells  or  cylinders  in  gallons  per 
foot  of  depth  or  length  :  —  Diameter  in  feet 
squared  X  4'9  (approximate). 

EQUIVALENT  PIPES.  —  To  find  how  many 
pipes  of  smaller  diameter  are  required  to 
discharge  the  same  quantity  as  one  large 
pipe:— 


Number  of  pipes  required  =     ,  — 

' 


Where  D  =  diameter  of  large  pipe  in  inches. 

Where  p  =  diameter  of  small  pipe  in  inches. 

DISTRIBUTION  OF  WATER.  —  In  determining 
sizes  of  distributing  mains  a  main  room  should 
be  provided  capable  of  yielding  the  maximum 
discharge  with  an  expenditure  of  head  in  over- 
coming friction  not  exceeding  25  %  of  the 
available  statical  head.  For  moderately  large 
pipes  3  ft.  per  second  is  generally  regarded 
as  a  suitable  rate  of  flow.  The  maximum 


rate  of  draught  upon  water  mains  may  be 
from  two  to  two-and-a-half  times  the  average 
consumption  during  the  24  hours.  The 
maximum  statical  head  upon  water  mains 
should  not  exceed  200  ft.,  or  about  86  Ibs. 
per  square  inch ;  and  for  an  effective  supply 
should  not,  if  possible,  be  less  than  100  ft. 
It  is  more  advantageous  to  have  ample  main 
room  than  to  rely  upon  excessive  statical 
head  as,  upon  occasions  of  heavy  draught, 
the  "  head "  will  be  rapidly  absorbed  in 
overcoming  frictional  resistance  in  the  mains. 
Turning  valves  on  and  off  too  suddenly  leads 
to  concussion  and  "  hammer,"  and  may  burst 
a  main. 

Hydraulic  Ram. — The  hydraulic  ram  is 
a  machine  which  is  largely  used  for  the  pur- 
pose of  raising  water  to  a  height  considerably 
above  the  top  of  the  "  fall "  or  head  available 
as  motive  power.  In  other  words,  the  appa- 
ratus utilises  the  momentum  of  a  stream  of 
water  falling  through  a  small  height  in  order 
to  lift  a  portion  of  that  water  to  a  greater 
height.  Thus  100  gallons  of  water  falling 
through  10  ft.  would  raise  10  gallons  to  a 
height  of  80  ft.,  or,  100  gallons  falling  5  ft. 
would  raise  1  gallon  to  an  elevation  of  some 
300  ft.  The  mechanism  of  the  hydraulic  ram  is 
designed  to  take  advantage  of  the  "  ramming  " 
force,  or  momentum  of  the  flow  of  water  in  a 
pipe  when  suddenly  arrested.  The  outline 
diagram  (Fig.  1)  illustrates  the  general 
arrangement  of  the  different  parts  of  a  system 
for  raising  water  by  means  of  a  hydraulic  ram. 
The  water  from  the  source  of  supply  flows 
down  a  "  drive-pipe  "  of  considerable  length, 
and  with  the  requisite  "  fall "  to  work  the 
ram  ;  when  the  water  approaches  its  maximum 
velocity  at  the  ram  its  flow  is  suddenly  and 
automatically  checked,  the  momentum  thus 
producing  a  rise  of  pressure  within  the  ram 
which  closes  the  "  waste  outlet  valve "  and 
forces  a  part  of  the  water  through  the 
"delivery  valve"  into  the  "air  vessel"  and 
"  delivery  main."  The  height  to  which  the 
water  is  thus  delivered  depends  upon  the 
amount  of  fall  available. 


232 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


HYD 


Under  ordinary  circumstances  it  may  be 
said  that  the  hydraulic  ram  returns  about 
50  %  of  the  natural  effect,  or,  in  other  words, 
the  quantity  of  water  raised  multiplied  by  the 
height  of  the  delivery  above  the  ram  will  be 
about  50%  of  the  quantity  of  water  working 
the  ram  multiplied  by  the  "  fall,"  in  the  same 
unit  of  time.  It  is  very  generally  estimated 
that  one-seventh  of  the  water  can  be  raised  to 
about  four  times  the  head  of  supply,  or  one- 
fourteenth  eight  times,  or  one  twenty-eighth 
sixteen  times,  thus  giving  a  useful  effect  of 
about  57  %.  Various  improvements  have 
been  introduced  during  recent  years  by  ram 
makers  in  regard  to  economy  of  drive  water 
and  other  matters,  and  in  the  Bailey's 
Decceur's  hydraulic  ram  one-third  of  the  drive 
water  is  forced  to  two-and-a-half  times  the 
height  of  fall,  one-sixth  to  five  times  the  fall, 
or  one-tenth  to  eight  times  the  fall,  giving 
a  return  of  about  83  %  of  the  natural  effect. 
In  determining  the  size  of  ram  suited  to 
any  particular  case,  it  will  be  necessary 
to  ascertain  the  fall  in  feet  available  from 
the  source  of  supply  to  the  site  of  the 
ram,  the  height  to  which  the  water  is  to 
be  raised,  the  horizontal  distance  from  the 
source  of  supply  to  the  place  of  delivery, 
and  the  quantity  of  water  required  to  be 
lifted  per  hour  or  day.  If  the  source  of  supply 
is  limited,  then  the  flow  should  be  accurately 
gauged  to  ascertain  the  yield  in  gallons  per 
minute.  An  approximate  idea  of  the  quantity 
of  water  which  should  be  available  at  the 
source  of  supply  for  the  purpose  of  working 
small  and  medium- sized  rams  may  be  gained 
from  the  fact  that  for  every  gallon  raised  some 
8  to  12  gallons  must  pass  through  the  ram. 
Larger  sizes  raising  water  to  high  elevations 
with  comparatively  low  falls  consume,  pro- 
portionately, more  water  in  working.  The 
quantity  of  driving  water  required  to  work  a 
ram  will  depend,  therefore,  upon  the  amount 
of  working  fall  available,  the  height  to  which 
the  water  is  to  be  raised,  and  the  quantity  of 
water  to  be  raised.  Under  suitable  conditions 
rams  can  be  worked  with  less  than  1  gallon 
of  water  per  minute.  The  diameter  of  the 


fall  or  injection  pipe  in  hydraulic  rams  is  very 
generally  about  twice  that  of  the  delivery  or 
rising  main.  The  length  of  the  supply  pipe 
may  be  made  from  five  times  to  ten  times 
the  height  of  the  "fall."  Any  working  fall 
from  about  18  in.  up  to  100  ft.  will  work  a 
ram,  but  the  greater  the  fall  obtained  up  to 
about  one-third  of  the  total  height  the  water 
has  to  be  raised  above  the  ram,  the  more 
economical  will  be  the  result,  i.e.,  the  ram 
will  cost  less  to  raise  a  given  quantity  and 
less  driving  water  will  be  required.  Where  a 
dam  cannot  be  formed  across  a  stream,  the 
requisite  fall  may  be  got  by  carrying  the  driving 
water  the  requisite  distance  down  the  stream  by 
means  of  stoneware  pipes  running  nearly  level 
until  the  necessary  fall  is  gained,  but  where 
the  driving  water  is  plentiful  a  small  working 
fall  will  suffice  with  a  more  powerful  ram,  and 


Hiqh,  Level 
TeinJc  or  Cistei-n, 


Diagram  showing  arrangement  of  Hydraulic  Ram. 

may  be  found  cheaper  than  obtaining  a  greater 
fall  and  using  a  small  ram.  Rams  will  force 
to  a  distance  of  several  miles,  some  firms 
guaranteeing  as  much  as  10  miles ;  and,  with 
a  sufficient  driving  water  and  working  fall  will 
force  to  any  height,  up  to  1,000ft.  As  one 
instance  of  a  high  lift  may  be  cited  that  of  a 
pair  of  Blake's  rams  worked  by  impure  stream 
water,  with  a  fall  of  only  9  ft.,  raising  4,500 
gallons  of  spring  water  per  day  to  a  height  of 
719  ft.  above  the  rams  (i.e.,  about  eighty  times 
the  height  of  the  working  fall),  and  to  a  distance 
of  1,223  yards  for  the  supply  of  a  large  horse 
stud  farm.  The  height  to  force  is  calculated 
from  the  level  of  the  ram  or  bottom  of  the 
working  fall.  The  usefulness  of  hydraulic 
rams  has  been  very  greatly  extended  by  the 
introduction  of  those  forms  in  which  the  water 
for  the  motive  power  is  obtained  from  one 


233 


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ENCYCLOPAEDIA   OF 


HYG 


source,  and  that  raised  for  use  from  another. 
This  is  accomplished  by  the  introduction  of  a 
cylinder  and  piston,  with  the  necessary  valves, 
between  the  working-barrel  or  main  pipe  of 
the  ram  and  the  delivery  pipe. 

A  hydraulic  ram  should  be  simple  and  strong 
in  design,  as,  when  fixed,  very  little  attention 
is  usually  given,  the  apparatus  frequently 
being  left  for  months  at  a  time.  The  air- 
chamber  should  be  of  tested  strength,  all 
joints  faced,  and  all  valves,  such  as  delivery, 
beat,  and  snifting  valves,  should  be  made  of 
gun  metal.  The  apparatus  is  a  very  useful 
and  economical  one  in  some  circumstances, 
will  work  even  when  flooded  with  water,  and 
requires  no  lubrication  or  packing  and  very 
little  attention. 

The  action  of  the  hydraulic  ram  is  some- 
what violent  and  noisy,  and  the  wear  and  tear 
necessarily  considerable.  These  objections 
are  largely  overcome  by  the  hydraulic  pressure 
pump,  by  means  of  which  a  large  quantity  of 
water  under  a  small  head,  flowing  slowly 
through  a  supply  pipe,  is  made  to  steadily 
raise  a  portion  of  the  water  to  a  higher  level. 
The  apparatus  consists  generally  of  a  large 
piston  working  vertically  in  a  cylinder  sur- 
mounted by  a  small  upper  cylinder,  in  which 
works  a  hollow  plunger  delivering  into  an  air 
vessel  from  which  the  delivery  pipe,  or  rising 
main,  is  taken  off  in  the  same  manner  as  in 
the  case  of  the  hydraulic  ram.  Where 
duplicate  cylinders  are  provided  the  apparatus 
can  be  made  to  deliver  water  steadily  and 
continuously. 

Hydrogel. — (See  "COLLOIDAL  MATTERS.") 

Hydro  -  Pneumatic  Systems.  —  (See 
"  EJECTOR.") 

Hydrosal.— -(See  "  COLLOIDAL  MATTERS.") 

Hydrostatic  Head.— The  pressure  due  to 
the  weight  of  liquids,  when  they  are  confined, 
is  proportional  to  the  height  of  the  column, 
and  is  equally  exerted  in  all  directions.  Any 


vessel  which  contains  a  liquid  has,  therefore, 
to  sustain  upon  each  point  a  pressure,  the 
intensity  of  which  will  vary  according  to  the 
height  or  head  of  the  liquid  above  that  point, 
but  which  will,  otherwise,  be  quite  indepen- 
dent of  the  shape  of  the  vessel.  As  an 
instance,  suppose  a  closed  tank  with  a  pipe 
projecting  vertically  from  its  top  and  that, 
both  are  filled  with  water ;  the  intensity  of 
the  pressure  upon  the  bottom  of  the  tank  will 
be  proportional  to  the  height  of  the  tank  plus 
that  of  the  pipe.  Again,  suppose  this  arrange- 
ment inverted,  with  the  end  of  the  pipe  closed ; 
the  pressure  per  square  inch  or  per  square 
foot,  as  the  case  may  be,  will,  at  the  bottom 
of  the  pipe,  be  precisely  as  it  was  at  the 
bottom  of  the  tank  when  in  its  former  posi- 
tion. The  large  "body"  of  water  in  the 
tank  does  not,  as  so  many  people  suppose, 
make  any  difference  whatever  to  the  intensity. 
From  this  it  follows  that  the  pressure  per 
square  inch,  for  example,  will  be  equal  to  the 
head  in  inches  multiplied  by  the  weight  of  a 
cubic  inch  of  the  liquid — the  same,  of  course, 
applies  to  any  other  unit  of  measurement. 
(See  article  on  "  HYDRAULIC  MEMORANDA.") 

E.  L.  13. 

Hygiene  and  Public  Health.  —  Defini- 
tion— Preventive  Medicine — Sanitary  Code  and 
Administration  --  Medical  Officer  of  Health 
— Acts  of  Parliament  —  Bye-Laws.  —  Hygiene 
is  defined  as  the  science  which  teaches 
us  how  to  keep  the  body  in  health  ;  but 
it  would  be  more  exact  to  define  it  as 
embracing  the  application  to  this  end  of  a 
whole  group  of  sciences  which  throw  light  on 
the  growth,  development,  and  vital  activities 
of  man.  It  aims  at  rendering  growth  more 
perfect,  life  more  vigorous,  decay  less  rapid, 
and  death  more  remote.  The  principles 
involved  and  the  scope  of  the  field  of  studv 
necessarily  embrace  every  circumstance  which 
affects,  for  good  or  evil,  man's  physical  wel- 
fare ;  or  in  other  words  all  those  factors, 
personal  and  environmental,  that  determine 
perfect  health.  It  is  not  possible  here  to  fully 
enunciate  those  principles;  the  object  and 


234 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


HYG 


scope  of  hygiene  and  public  health  can  only 
be  broadly  defined.  The  importance  of  the 
subject  from  the  standpoints  both  of  the 
individual  and  the  State,  cannot  well  be 
exaggerated,  for  it  seeks  to  promote  that 
physical  health  which  determines  in  such 
large  measure  the  happiness  and  productive- 
ness of  the  individual.  The  value  of  the 
observance  of  the  laws  of  hygiene  are,  from 
the  communal  standpoint,  largely  economic  ; 
nothing,  for  instance,  is  so  costly  as  disease, 
and  just  as  the  employer  of  labour  gains,  both 
in  the  quantity  and  quality  of  work  performed, 
by  paying  due  regard  to  the  sanitary  environ- 
ment of  his  workers,  so  does  the  State  reap 
a  material  benefit  by  promoting  wise  public 
health  legislation, that  physical  efficiency  which, 
while  promoting  moral  and  mental  health, 
also  increases  that  vigour  and  productiveness 
of  the  community  which  determine  national 
prosperity.  Seeing,  then,  that  it  is  a  prime 
matter  of  State  concern  that  the  public  health 
should  be  conserved,  and  recognising  that  the 
individual  is  often  ignorant  or  helpless  in 
these  respects,  the  State  has  sought  to  pro- 
mote the  general  health  by  public  health 
legislation  and  to  provide  the  necessary 
machinery  to  give  it  effect. 

PREVENTIVE  MEDICINE. — Hygiene  is  essen- 
tially preventive  medicine,  but  it  also  embraces 
matters  which  are  beyond  the  province  of 
medicine.  A  convenient  subdivision  of  this 
great  subject  may  be  made  into  (1)  General 
and  personal  hygiene ;  (2)  Special  hygiene  ; 
(3)  Public  health.  General  hygiene  embraces 
those  external  or  environmental  conditions 
of  locality,  site,  dwelling,  air,  water-supply, 
soil,  refuse  and  sewage  disposal,  &c.,  which 
determine  healthy  life  ;  while  measures  which 
relate  more  particularly  to  the  individual's 
person,  and  are  so  largely  dependent  upon 
individual  habits  and  initiative  for  their 
observance,  are  included  in  the  sphere  of 
personal  hygiene.  Thus  bathing,  washing, 
clothing,  food  and  diet,  exercise,  &c.,  are 
matters  of  personal  hygiene.  Special  hygiene 
embraces  the  hygiene  of  special  circumstances, 
as,  for  instance,  school  hygiene,  industrial 


hygiene,  military,  naval,  and  tropical  hygiene. 
Public  health  in  the  sense  of  State  hygiene 
may  be  taken  to  embrace  the  legal  pro- 
visions and  the  administrative  measures 
which  are  designed  to  protect  the  health 
interest  of  the  community,  such  as  the  pre- 
vention of  the  spread  of  infectious  disease, 
the  prevention  of  unwholesome  conditions  in 
the  community,  the  protection  of  the  public 
water  and  food  supply,  and  generally  the 
removal  of  nuisances  which,  by  favouring  the 
prevalence  of  disease,  may  act  as  foci  of  infec- 
tion to  the  community.  Much  remarkable 
testimony  is  forthcoming  to  the  benefits  which 
have  accrued  from  the  application  of  the  laws 
of  hygiene ;  as,  for  instance,  the  great  reduc- 
tion in  sickness  and  mortality  among  sailors 
in  our  navy,  among  the  soldiers  in  our  army, 
among  the  prisoners  in  our  gaols,  and  the 
occupants  of  our  hospitals,  factories,  work- 
shops, &c. ;  and  the  effect  of  the  growth  of 
public  health  legislation  and  administration 
and  of  an  increasing  realisation  by  the  people 
of  the  importance  of  the  demands  of  sanita- 
tion, is  shown  by  the  reduced  death-rate  from 
all  causes  and  from  certain  special  diseases 
(more  particularly  certain  communicable  dis- 
eases) ;  while  the  increase  in  the  mean  duration 
of  life  of  all  classes  is  no  less  noteworthy. 
If  it  is  conceded  that  the  observation  of  the 
laws  of  hygiene  leads  to  the  survival  of  some 
who  would  otherwise  have  succumbed  as  the 
result  of  the  law  of  the  survival  of  the  fittest, 
then  it  must  be  conceded  also  that  preventable 
disease  does  not  kill  only ;  too  often  it  maims 
or  enfeebles  ;  so  that  in  a  substantial — per- 
haps in  a  very  large — proportion  of  cases  it 
subtracts  the  patients  whom  it  may  ulti- 
mately spare  from  the  sum  of  the  vigorous 
and  adds  them  to  the  sum  of  the  relatively 
inefficient. 

SANITARY  CODE  AND  ADMINISTRATION. — It  may 
be  said  that  no  other  country  possesses  a 
sanitary  code  and  administration  so  complete 
as  that  of  Great  Britain.  The  provision  for 
public  health  administration  in  this  country 
includes  the  Local  Government  Board  (a 
central  authority  directly  under  Government), 


235 


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ENCYCLOPEDIA   OF 


HYG 


county  councils,  borough  councils,  urban  and 
rural  sanitary  authorities,  and  their  respective 
staffs  of  officials.  The  Local  Government 
Board  is  charged  with  some  measure  of  con- 
trol and  supervision  of  Poor  Law  and  Public 
Health  Administration  (including  vaccination) 
throughout  the  country.  For  these  purposes 
a  large  staff  of  skilled  advisers  and  inspectors 
has  been  appointed,  and  a  National  Vaccine 
Establishment  for  the  supply  of  vaccine-lymph 
is  maintained.  The  more  important  powers 
and  duties  of  the  Local  Government  Board 
may  be  summarised  as  follows :  To  issue 
regulations  and  instructions  with  reference  to 
the  prevention  and  suppression  of  epidemic 
disease ;  to  inspect  vaccination ;  to  regulate 
the  borrowing  powers  of  local  authorities,  by 
inquiring  into  projects  of  sanitary  improve- 
ment relative  to  housing  of  the  poor,  sewage 
disposal,  water-supply,  hospitals,  &c.,  when 
the  projects  involve  the  raising  of  a  loan  for 
their  undertaking ;  to  revise  and  approve 
local  sanitary  bye-laws ;  to  sanction  or  veto 
the  appointment  of  local  sanitary  officials, 
when  the  State  pays  a  moiety  of  the  salaries 
of  such  officers.  The  Home  Office  deals  with 
the  conditions  of  labour  in  factories  and  work- 
shops, &c.,  and  possesses  a  staff  of  inspectors 
charged  with  many  duties  under  the  provi- 
sions of  the  Factory  and  Workshops  Acts, 
&c.,  and  the  Orders  issued  from  time  to  time. 
County  councils  supervise  generally  the 
sanitary  administration  throughout  the 
county,  and  may  report  a  defaulting  sanitary 
authority  to  the  Local  Government  Board. 
They  are  also  given  certain  administrative 
powers  in  reference  to  public  health  matters  ; 
they  are,  for  instance,  charged  with  the 
administration  of  several  important  public 
health  measures,  namely,  the  Rivers  Pollution 
Prevention  Act,  the  Education  Act,  the  Mid- 
wives  Act,  the  Isolation  Hospitals  Act,  the 
Contagious  Diseases  Animals  Acts,  1878  to 
1886.  The  several  sanitary  areas  comprised 
within  the  county  are  constituted  either 
boroughs,  urban  or  rural  sanitary  districts; 
and  the  borough  or  district  councils  are 
charged  with  the  local  administration  of  the 


bulk  of  public  health  legislation.  To  assist 
in  the  satisfactory  performance  of  these  duties 
a  clerk,  a  medical  officer  of  health,  a  surveyor, 
and  one  or  more  sanitary  inspectors  are 
appointed  to  serve  each  local  authority. 

MEDICAL  OFFICER  OF  HEALTH.  -  -  The 
duties  of  the  medical  officer  of  health,  as 
defined  by  the  Local  Government  Board, 
require  that  he  shall  inform  himself  respect- 
ing all  influences  which  may  injuriously  affect 
the  public  health  in  his  district,  and  advise 
the  sanitary  authority  thereon  ;  that  he  shall 
investigate,  report  and  advise  upon  outbreaks 
of  contagious,  infectious,  or  epidemic  disease, 
and  give  immediate  information  to  the  Local 
Government  Board  and  county  council  of  any 
outbreak  of  dangerous  infectious  disease ;  that 
he  shall  deal  with  unsound  food,  offensive 
trades,  &c.,  and  shall  furnish  an  annual 
report  ;  subject  to  the  instructions  of  the 
sanitary  authority  he  shall  direct  or  super- 
intend the  work  of  the  sanitary  inspector. 
The  duties  of  a  sanitary  inspector  relate  to 
the  inspection  of  nuisances,  of  offensive 
trades,  food,  &c. ;  the  procuring  of  samples 
under  the  Sale  of  Foods  and  Drugs  Acts,  and 
the  taking  of  measures,  under  the  direction 
of  the  medical  officer  of  health,  for  prevent- 
ing the  spread  of  dangerous  infectious 
disease. 

ACTS  OF  PARLIAMENT. — The  chief  Acts  of 
Parliament  which  have  reference  to  the  public 
health  embrace  measures  to  guard  the  health 
interests  of  all  classes  of  the  community,  from 
the  cradle  to  the  grave.  Indeed  the  practical 
realisation  of  the  true  scope  of  preventive 
medicine  is  one  of  interesting  evolution. 
Preventive  medicine  at  first  took  cognizance 
of  little  else  than  dangerous  infectious  disease 
and  prescribed  certain  measures  of  precaution 
almost  exclusively  when  these  diseases  reached 
epidemic  proportions.  Then  followed  the 
adoption  of  measures  directed  towards  ensur- 
ing an  improved  sanitary  environment  for 
the  people.  These  mainly  related  to  the 
drainage  arrangements  and  water  supply ; 
in  fact,  at  first  they  went  little  further,  and 
it  is  only  comparatively  recently  that  the 


236 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


HYG 


fuller  needs  of  hygienic  environment  began 
to  receive  the  attention  their  importance 
demands.  Personal  hygiene  remained  rela- 
tively neglected  for  what  were  conceived  to 
be  the  superior  claims  of  sanitary  environ- 
ment ;  but  when  the  broader  horizon  of 
preventive  medicine  was  illumined  by  a  truer 
conception  of  its  scope  and  demands,  it  was 
r  ecognised  that  the  personal  and  social  cir- 
cumstances of  the  community  were  at  the 
root  of  the  main  difficulties  with  which  pre- 
ventive medicine  had  to  contend.  The  fact 
is  now  generally  appreciated  that  the  hygienic 
well-being  of  the  community  will  be  deter- 
mined more  by  education  and  training, 
developing  individual  desire  and  initiative, 
than  by  legal  enactment. 

While  therefore  we  possess  in  several  Public 
Health  Acts  the  power  which  enables 
administrative  bodies  to  provide  the  sanitary 
environment  of  the  individual,  whether  at 
home  or  in  the  workshop  or  factory,  legal 
measures  have  more  recently  appeared  upon 
the  statute  book  which  mainly  concern 
themselves  with  the  personal  demands  of 
hygiene. 

It  is  only  possible  here  to  schedule  the 
more  important  legal  enactments  which  are 
embraced  in  the  public  health  legislation  of 
this  country.  They  are  as  follows :  The 
Public  Health  Acts  of  England  and  Wales, 
London,  Scotland,  and  Ireland — including 
certain  Public  Health  Amendment  Acts,  the 
more  recent  of  which  is  the  Amendment  Act 
of  1907.  These  Acts  contain  provisions 
dealing  with  conditions  which  are  nuisances 
or  injurious  to  health,  offensive  trades,  water 
supply,  house  drainage,  sewerage  and  sewage 
disposal,  scavenging  and  cleansing,  houses  let 
in  lodgings,  common  lodging-houses,  under- 
ground rooms,  unsound  food,  slaughter-houses, 
dangerous  infectious  diseases,  and  disinfection. 

The  Local  Government  Acts,  1888,  1894. 

The  Midwives  Act,  1902. 

The  Births  and  Deaths  Registration  Act, 
1874. 

The  Notification  of  Births  Act,  1907. 

The  Infant  Life  Protection  Act,  1897. 


The  Education  (Administrative  Provisions) 
Act,  1907. 

The  Employment  of  Children  Act,  1903. 

The  Provision  for  Meals  for  Children  Attend- 
ing Public  Elementary  Schools  Act,  1906. 

The  Prevention  of  Cruelty  to  Children  Act, 
1894. 

The  Children's  Act,  1908. 

The  Shop  Hours'  Acts,  1886,  1892,  1904. 

The  Factories  and  Workshops  Acts,  1891, 
1895,  1907. 

The  Alkali,  etc.,  Works  Regulation  Act,  1881, 
1892. 

The  White  Phosphorous  Matches  Prohibi- 
tion Act,  1908. 

The  Housing  of  the  Working  Classes  Acts, 
1890,  1900,  1903. 

The  Customs  and  Inland  Revenue  Act,  1890, 
1903. 

The  Open  Spaces  Acts,  1887,  1890. 

The  Infectious  Disease  Notification  Acts, 
1889  and  1899. 

The  Infectious  Diseases  Prevention  Act, 
1890. 

The  Isolation  Hospitals  Act,  1893. 

The  Vaccination  Acts,  1867,  1871,  1898, 
1907. 

The  Cleansing  of  Persons  Act,  1897. 

The  Aliens  Act,  1905. 

The  Inebriates  Act,  1898. 

The  Public  Health  (Interments)  Act,  1879. 

The  Burial  Acts,  1854,  1855,  1857. 

The  Cremation  Act,  1902. 

The  Public  Health  Water  Act,  1878. 

The  Rivers  Pollution  Prevention  Acts,  1876, 
1893. 

The  Canal  Boats  Acts,  1877,  1884. 

The  Sale  of  Foods  and  Drugs  Acts,  1875  to 
1899. 

The  Sale  of  Horseflesh  Act,  1889. 

The  Margarine  Act,  1887. 

The  Butter  and  Margarine  Act,  1907. 

The  Public  Health  (Regulations  as  to  Food) 
Act,  1907. 

In  addition  there  are  in  force  many  orders, 
bye-laws  and  regulations  which  are  authorised 
by  Acts  of  Parliament.  The  more  important 
orders  are  the  Dairies,  Cowsheds  and  Milkshops 


237 


INC 


ENCYCLOPAEDIA   OF 


IND 


Orders  of  the  Local  Government  Board, 
1885,  1899,  and  several  orders  issued  by  the 
Home  Office  relating  to  factories  and  work- 
shops. Among  the  regulations  issued  by  the 
Local  Government  Board  special  mention 
should  be  made  of  those  designed  to  prevent 
the  importation  of  cholera,  yellow  fever,  and 
plague  into  these  islands,  and  those  relating  to 
canal  boats,  and  to  the  importation  of  unsound 
food  and  foreign  meat;  while  among  the 
regulations  which  local  sanitary  authorities 
are  empowered  to  make,  those  relating  to 
dairies,  cowsheds,  and  milkshops,  and  the 
removal  to  and  the  detention  in  hospital  of 
infectious  patients  removed  from  ships  and 
vessels,  are  of  special  importance. 

BYE-LAWS. — Subject  to  the  approval  of  the 
Local  Government  Board  many  bye-laws  are 
authorised  to  be  made  by  local  sanitary 
authorities,  and  to  assist  those  bodies  in 
framing  such  bye-laws  the  Board  has  issued 
a  series  of  model  bye-laws.  Bye-laws  may 
be  made  dealing  with  houses  let  in  lodgings, 
offensive  trades,  common  lodging  houses,  new 
buildings,  slaughter-houses,  cleansing  and 
scavenging,  the  prevention  of  certain  nuis- 
ances, mortuaries,  &c. 

Finally,  the  public  health  legislation  of  this 
country  includes  many  local  improvement 
Acts  which  only  relate  to  the  particular  dis- 
trict for  which  the  special  powers  have  been 
sought  and  obtained.  These  Acts  are  now 
numerous,  and  they  constitute  an  important 
addition  to  the  sanitary  legislation  of  the 
country.  As  instances  of  such  Acts,  the 
London  County  Councils  General  Power  Acts 
and  the  Sheffield  Corporation  Act,  1903,  for 
the  compulsory  notification  of  consumption 
in  that  city,  may  be  cited.  H.  B.  K. 


Incandescent  Lamps. — (See 
CITY"    and  "  GAS.") 


ELECTKI- 


Indicator. — The  Expansive  Use  of  Steam — 
Condensing. — All  good  class  modern  steam 
pumping  machinery  must  be  designed  and 
worked  with  a  careful  regard  to  fuel 
economy,  and  smallness  of  steam  con- 


sumption of  the  engines.     To  this  end  the 
tendency  for  many  years  has  been  towards 
the  employment  of  high-pressure  steam,  used 
expansively  in   either    two,    three,    or    four 
stage   compound    engines     (more    commonly 
spoken  of  as  compound,  triple,  and  quadruple 
engines   respectively),  the   use   of   high-duty 
valve  gears,  and  many  other  improvements 
having  for  their  common  object  the  produc- 
tion of  the  largest  possible  amount  of  work 
from    any    given    weight    of    steam    passing 
through  the  cylinders.     At  works  using  large 
quantities  of  steam  power,  as  in  the  case  of 
water  or  sewage  pumping  stations,  where  the 
coal  bill  necessarily  becomes  a  considerable 
item  in  the  annual  expenditure,  it  is  therefore 
of  primary   importance    that    the    engineer 
should  be  well  acquainted  with  the  best  avail- 
able means  of  frequently  and  fully  investigating 
the  behaviour  of  the  steam  in  the  cylinders  of 
the  various  engines  that  may  be   under  his 
charge.    Any  neglect  to  systematically  perform 
such  investigations  may,  even  in  a  station  of 
medium  size,  easily  involve  the  waste  of  con- 
siderable sums  annually  in  fuel  for  the  want 
of  a  knowledge  of  the  efficiency  of  the  per- 
formance  of   each    individual  engine.       The 
need  for   some    convenient    means    of    thus 
investigating  the  work  of  his  engines  was  first 
realised  by  James  Watt,  who  introduced  the 
"steam-engine  indicator,"  an  instrument  for 
the  purpose  of  describing  a  diagram,  the  area 
of  which  has  a  definite  relation  to  the  amount 
of  work  done  upon  the  piston  by  the  steam  in 
the  cylinder.     It  will  not  be  necessary  to  here 
describe  the  indicator  in  detail,  but  it  may 
briefly  be  stated  to  consist  of  a  small  cylinder 
communicating  with  the  engine  cylinder,  and 
fitted  with  a  small  piston,  which  the  varying 
steam  pressure  drives    upward    against    the 
resistance  of  a  spring  of  a  stiffness  suited  to 
the  pressure.      A  lever,  connected  with   the 
piston-rod  of  the  indicator,  imparts  motion  to 
a  pencil,  which  traces  the  diagram  on  a  card 
wrapped  round   a   vertical   drum,    which    is 
turned  backwards  and  forwards  by  means  of 
a  string    connected    with    the   piston-rod   of 
the  engine.     The  figure  thus  drawn  by  the 


238 


IND 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


IND 


indicator  shows  the  varying  pressure  acting 
upon  the  piston  of  the  engine  at  every  point  of 
the  stroke;  the  mean  pressure  is  thence  readily 
ascertained,  and  the  power  of  the  engine 
calculated.  The  indicator  diagram  also  affords 
invaluable  information  as  to  the  interaction 
of  the  steam  and  cylinder  walls,  and  enables 
defects  in  the  design,  setting,  and  working  of 
the  valves  for  the  admission  and  exhaust  of 
steam  into  and  out  of  the  cylinder  to  be 
detected  and  remedied,  and  the  economy  of 
the  engine  thus  improved.  By  the  teachings 
of  the  diagram  of  work  performed  the  advan- 
tages of  the  expansive  use  of  steam,  com- 
pounding and  condensing,  can  alone  be 
fully  appreciated. 

A  theoretical  indicator-diagram  of  work 
upon  the  piston  in  a  condensing  engine, 
with  early  "cut-off"  of  steam,  is  shown 
in  Fig.  1,  and  serves  to  illustrate  the 
advantage  of  expanding  steam  in  a  single 
cylinder  instead  of  using  full  pressure  to 
the  end  of  the  stroke.  It  will  be  seen  that 
full  steam  is  used  during  a  small  portion 
only  (.4  F)  of  the  stroke  of  the  piston,  the 
remainder  being  completed  by  the  pres- 
sure of  the  expanding  steam;  that  the 
pressures  gradually  fall  as  the  end  of  the 
stroke  is  approached,  as  roughly  repre- 
sented by  the  hyperbolic  curve  D  H.  The  area 
of  the  diagram  is  a  measure  of  the  work  done, 
and  the  portion  B  C  D  E  represents  that 
performed  by  the  "  full  steam  "  without  con- 
densation, E  D  II  J  that  done  by  expansion 
without  condensation,  and  A  B  J  G  that 
resulting  from  the  use  of  the  condenser.  It  is 
thus  seen  that  by  "condensing,"  by  the  use 
of  high-pressure  steam  and  expansive  working, 
great  economy  is  obtainable  by  the  introduc- 
tion of  an  earlier  "  cut-off,"  and  a  higher 
ratio  of  expansion,  thus  using  at  each  stroke 
a  less  weight  of  live  steam, 

In  all  modern  economical  steam  plants  of 
any  considerable  size,  the  tendency  is  towards 
the  use  of  high-pressure  steam  and  high  ratios 
of  expansion  in  the  cylinders.  For  this 
purpose  a  compound  engine  having  two, 
three,  or  even  four  cylinders,  becomes  neces- 


sary. Theoretically,  there  is  no  difference  in 
the  expansive  power  of  steam  of  given  initial 
and  terminal  pressure,  whether  effected  in 
one  or  two  cylinders,  provided  the  compound 
cylinders  are  correctly  proportioned.  The 
single-cylinder  engine  has  considerable  theo- 
retical advantage  over  the  compound  engine, 
but,  practically,  the  advantage  lies  decidedly 
with  the  compound  principle.  This  arises 
from  thfi  circumstance  that  although  very  high 
rates  of  expansion  are  theoretically  possible 
in  the  single-cylinder,  the  practical  economical 
limits  are  soon  reached,  because  high  ratios 
of  expansion  involve  high  initial  pressures  and 


Length  of  Stroke 

Full  Exhaust 


L 


Back  Pressure 


Point  of  Admission 


FIG.   1.- 


-Theoretical  Indicator  Diagram — Condensing 
Engine. 


great  differences  of  temperature  between  live 
and  exhaust  steam.  When  the  live  steam 
enters  a  relatively  cold  cylinder  a  considerable 
initial  condensation  takes  place,  thereby 
largely  neutralising  the  advantage  of  a  high 
expansion  ratio.  This  difficulty  is  met  by 
permitting  the  steam  to  successively  expand 
in  either  one,  two,  three,  or  even  four  cylinders, 
according  to  the  initial  pressure  of  the  steam 
used,  and  the  ratio  of  expansion  adopted. 
We  thus  have  what  are  known  as  the  single, 
compound,  tfiple,  and  quadruple  forms  of 
engines  respectively,  and  it  is  in  thus  dim- 
inishing the  effects  of  initial  condensation 
with  high  expansion  ratios  that  the  main 
advantage  of  "  compounding  "  lies.  There  is, 
however,  a  further  advantage  in  that  the 
multiple  cylinder  engine  lends  itself  to  the 
equal  division  of  the  work  between  two  or 


239 


IND 


ENCYCLOPAEDIA  OF 


IND 


three  cranks  set  at  angles  of  90°  or  120°  with 
each  other,  thus  giving  a  more  equable  turning 
effect,  and  avoiding  dead  centres.  In  the 
distribution  of  the  steam  between  two  or  three 
cylinders,  each  piston  should  give  to  its  crank 
as  near  as  possible  an  equal  amount  of  work, 
and  there  should  also  be  an  approximately 
equal  fall  of  temperature  in  the  different 
cylinders. 

From  what  has  been  said  it  will  be  gathered 
that  a  high  initial  pressure  is  necessary  in 
order  to  get  the  full  advantages  to  be  derived 
from  the  use  of  steam  in  the  compound  and 
triple-c}7linder  engine.  For  compound  engines 
a  pressure  of  from  90  Ibs.  to  120  Ibs.  per  square 
inch  is  required,  and,  where  a  steam  pressure 
of  150  Ibs.  is  available,  triple  expansion  engines 


Full  Sieam 


-Point  of  Cutoff 


Point  of  Admission 
Point  of  Compression 
Exhaust 


^Re/ease 


Line 


FIG.    2. — Actual 


Indicator   Diagrain- 
Enyine. 


will  be  more  economical  than  compound. 
Higher  pressures  still  are  necessary  for  the 
quadruple  expansion  engine,  but  these  are 
seldom  used  for  municipal  purposes. 

The  actual  indicator  diagram,  as  taken  from 
the  steam  engine,  differs  considerably  from  the 
theoretical  diagram  given  in  Fig.  1,  and 
may  be  considered  under  two  heads,  viz., 
those  from  non-condensing  engines  and  those 
from  condensing  engines.  From  the  study  of 
the  diagram  from  any  given  engine,  much 
useful  information  may  be  obtained  in  addition 
to  the  power  of  the  cylinders  indicated  by 
carefully  observing  the  nature  of  the  deviations 
from  the  theoretical  diagram.  The  diagram 
shown  in  Fig.  2  is  from  a  non-condensing 
engine,  that  is,  one  which  exhausts  directly 
into  the  atmosphere.  It  will  be  noticed  that 
from  the  point  of  admission  the  steam  pressure 
at  once  rises,  and  is  well  maintained  to  the 
point  of  cut-off,  where  a  slight  "  wire-draw- 


ing "  of  the  steam  is  indicated  by  the  rounded 
corner  of  the  diagram.  The  absence  of  any 
such  wire-drawing  in  a  diagram  points  to  the 
efficiency  of  the  valve  gear.  From  the  point 
of  cut-off  the  steam  works  expansively  through 
the  remainder  of  the  stroke  till  the  "  release  " 
of  the  exhaust  steam  occurs  at  the  point  indi- 
cated. The  exhaust  line  of  the  diagram  falls 
to  the  atmospheric  line  through  the  exhausting 
of  the  steam  being  well  carried  out  without 
back-pressure,  and  a  small  amount  of  "  com- 
pression "  takes  place  on  the  return  of  the 
piston  before  the  admission  of  a  fresh  supply 
of  live  steam  to  the  cylinder.  A  larger  amount 
of  compression  than  that  shown  would 
advantageously  tend  to  decrease  the  amount 
of  initial  condensation  in  the  cylinder,  and  to 
produce  smoother  working  in  the  engine. 

A  practical  indicator  diagram  from  a 
condensing    engine    (that    is    one    which 
exhausts  into  a  vacuum)  is  given  in  Fig.  3, 
which  fully  explains  the  functions  of  the 
different  parts  of  such  a  diagram.     Fol- 
lowing the  diagram  round  from  the  point 
of     admission    of    the     steam    (M)    the 
-Non-condensing       following   cycle    of    operations    occurs   ;it 
each    stroke.      Upon    the    admission    of 
live    steam    the    "  clearance "    space    is   first 
filled,  and  the  pressure  in  the  cylinder  then 
rises  to  E,  whereupon  the  piston  moves  forward 
under  full  steam  to  the  point  of  cut-off.    From 
this  point  the  forward  stroke  is  completed  by 
the  expansive  force  of  the  steam  to  the  point 
of   release.     Upon    the    release    opening    to 
exhaust  the  pressure  at  once  falls  to  J,  and 
the  piston  returns  because  the  vapour  pressure 
in  the  condenser  cannot  be  wholly  removed, 
thus   showing  a  certain  amount   of    "  back- 
pressure," as  in  the  diagram.     The  exhaust 
ports  being  fully  open  on  the  return   of  the 
piston  from  J  to  K,  a  horizontal  line  is  drawn 
till  the  point  of  compression  is  reached  and 
the  remaining  steam  is  compressed  to  M,  the 
point  of  admission.  Here  it  meets  the  incoming 
live    steam   due   to   the  advance  opening   or 
"lead"  of  the  valves  immediately  before  the 
commencement  of  a  new  stroke,  and  the  steam 
pressure  again  rises  to  point  E.     In  practice, 


240 


IND 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


IND 


there  are  many  variations  in  form  from  this 
diagram,  and  it  is  by  observing  these  differ- 
ences from  time  to  time  that  defects  in  the 
working  of  an  engine  are  detected.  For 
example,  if  the  "  full-steam  "  line  falls  in  the 
manner  shown  by  the  dotted  line  E  F  G,  it 
indicates  "  wire-drawing  "  at  the  point  of  cut- 
off on  account  of  narrow  steam  ports,  insuffi- 
ciency of  valve  opening,  or  throttling,  and 
the  steam  is  thus  prevented  from  following  up 
the  piston  at  full  pressure.  The  common 
slide  valve,  actuated  by  an  ordinary  eccentric, 
owing  to  the  slowness  with  which  it  closes  the 
port,  always  produces  a  certain  amount  of 
wire-drawing.  To  obtain  a  perfect  cut-off 
the  valve  must  open  quickly, 
remain  open  till  the  point  of  cut- 
off, and  then  close  quickly.  There 
are  several  special  valve  devices 
designed  to  meet  these  conditions, 
of  which  the  Corliss  valve  gears, 
which  are  very  perfect  in  their 
action,  are  perhaps  the  best 
known,  and  have  the  merit  of 
producing  a  very  sharply  denned 
diagram.  A  moderate  amount  of 
"  compression  "  is  shown  in  the 
diagram  from  K  to  M.  This  is 
brought  about  by  closing  the 
exhaust  port  a  little  before  the 
piston  has  completed  its  stroke, 
thus  compressing  the  steam  still 
remaining  in  the  cylinder  into  the  clearance 
spaces.  The  extent  of  compression,  or 
"cushioning,"  which  may  be  advantageously 
employed  depends  mainly  upon  the  speed  of 
the  engine.  A  large  amount  of  cushioning 
is  required  in  high-speed  engines  to  arrest  the 
momentum  of  the  rapidly  moving  parts,  but 
in  engines  with  a  slow  piston  speed  a  moderate 
compression  will  be  sufficient  to  ensure  smooth 
running.  In  engines  having  great  piston 
speed  and  high  ratio  of  expansion  the  exhaust 
steam  may  be  compressed  up  to  the  initial 
pressure  of  the  steam,  in  which  case  the 
cylinder  becomes  heated  to  the  initial  tempera- 
ture, and  the  condensation  of  the  fresh  live 
steam  upon  entry  is  thereby  greatly  reduced. 


Cushioning  is  partly  effected  by  giving  the 
slide  valve  the  requisite  amount  of  "  lead," 
that  is,  allowing  it  to  open  the  steam  port 
before  the  piston  arrives  at  the  end  of  the 
stroke.  Want  of  lead  on  the  valve,  causing 
late  admission  of  the  steam,  shows  itself  upon 
the  diagram  by  a  rounded  corner  such  as  C  to 
D,  or  if  very  marked  by  a  sloping  admission 
line  as  from  A  to  B  owing  to  the  piston  having 
travelled  through  a  part  of  the  stroke  before 
full  pressure  is  upon  it.  In  addition  to  the 
admission  of  steam  before  the  end  of  the 
stroke,  it  will  be  observed  from  the  diagram 
that  its  release  on  the  other  side  of  the  piston 
also  takes  place  before  the  end  of  the  stroke. 


1 


—  \          —  —  tS]£^tLe—  —  —rJLs£u—eV—lI— 
Mt  "Tf-Po/nt  of  Adrfiission  of  Steam 
/•Point  ^Compression 
x  K      Full     ^  ^Exhaust 


'  /3_  N  Back  Pressure 

r T ~ — * 1 

Pressure  in  Condenser  \ 


'Absolute  Vacuum  or  Zero  line 
k= Stroke >j 

MtoK'  Compression 
PIG.  3. — Actual  Indicator  Diagram — Condensing  Engine. 

This  prevents  excessive  back  pressure,  and 
has  the  effect  of  rounding  that  end  of  the 
diagram  as  shown.  If  the  steam  were  carried 
to  the  end  of  the  stroke  before  opening  to 
exhaust  the  diagram  would  approximate  to 
the  form  shown  by  the  line  H  J  indicating 
excessive  and  wasteful  back  pressure. 

A  leaky  piston  produces  a  diagram  with  a 
loop  enclosing  minus  effective  pressure — the 
pressures  on  each  side  of  the  piston  tending 
to  equalise,  and  initial  condensation  is  shown 
by  the  sudden  falling  off  of  the  pressure  and 
corresponding  fall  of  the  expansion  curve  from 
the  point  of  cut-off.  This  and  re-  evaporation 
may  be  detected  by  drawing  the  hyperbolic 
expansion  curve.  By  the  same  means  the 


M.S.E. 


241 


IND 


INT 


effect  of  a  leaky  slide  valve  upon  the  diagram 
would  be  revealed  as  it  would  raise  the  expan- 
sion  curve   at   the   expense    of    live    steam. 
Excessive  compression  would  produce  an  effect 
upon  the  diagram  similar  to  that  shown  by  the 
dotted  line  N  P  E  (Fig.  3).    An  indicator  with 
too  light  a  spring  or  too  heavy  a  piston  pro- 
duces a  shaky  diagram  having  a  wavy  outline. 
Reference  has  been  made  above  to  the  hyper- 
bolic expansion  curve,  and  it  may  be  convenient 
here  to  observe  that  steam  is  not  a  perfect 
gas  capable  of  expanding  in  strict  accordance 
with  Boyle's  law,  nor  is  the  curve  of  its  expan- 
sion strictly  represented  by  a  hyperbola.    The 
expansion  line,  however,  of  a  good  diagram 
approximates    to    the    hyperbolic    curve    so 
closely  that  it  is  used  as  a  convenient  datum 
for  purposes  of  comparison.     Its  application 
in  this  connection  frequently  enables  defects 
in    the   diagram,    and    consequently   in    the 
action   of   the   steam  valves,  to   be   detected 
which  might  otherwise  have  escaped  observa- 
tion.    On  the  left  hand  side  of  the  diagram 
(Fig.    1)     will    be     noted    a     space    marked 
"  clearance,"  and  to  which  further  reference 
must  be  made.     The  piston  of  an  engine  in 
practice  does  not,  at  the  end  of  its   stroke, 
come  quite  close  up  to  the  end  of  the  cylinder. 
The  small  space  thus  left  between  piston  and 
cover  is  necessary  to  allow  for  the  wear  of  the 
journals  and  affords  room  for  any  condensed 
steam    or    priming   which    may   occur.      In 
addition  to  this  there  is  also  the  volume  of 
the  steam  ports  between  the  valve  faces  and 
the  cylinder.      The   spaces    are    collectively 
known  as  the  clearance  of  the  cylinder,  and 
have  an  important  bearing  upon  the  expansion 
of  the  steam  and  the  economy  of  the  engine 
as  they   have   to    be  filled  with  steam  when 
"  admission  "  occurs.      Clearance,   therefore, 
influences   the    thermodynamic   efficiency   of 
the  engine  mainly  by  altering  the  consump- 
tion of  steam  per  stroke.  Neglecting  clearance, 
the  ratio  of  expansion  of  steam  in  a  cylinder, 
is  equal  to  the  volume  of  the  cylinder  divided 
by  the  volume  to  the  point  of  cut-off,  but  if 
clearance  be  taken  into  account  the  true  ratio 
of  expansion  is  much  less.     Thus,  referring 


back  to  Fig.  1,  if  P  A7  represents  the  volume 
swept  through  by  the  piston  up  to  the  point 
of  release,  K  P  the  volume  of  the  clearance, 
and  P  S  the  volume  swept  through  during 
admission  or  to  cut-off,  then  the  apparent  ratio 
of  expansion  is  P  N/P  S,  whereas  the  real  ex- 
pansion is  (K  P+P  N)/(K  P  +  P  S).  The  losses 
arising  from  clearance  cannot  in  practice  be 
avoided  altogether,  but  may  be  considerably 
reduced  by  the  "compression"  of  a  portion 
of  the  steam  on  the  return  stroke  as  already 
explained.  W.  H.  M. 


Infectious 

DISEASES.") 


Diseases. — (See      "  ZYMOTIC 


Intake. — In  water  supply  the  "  intake  "  is 
the  source  or  point  on  the  banks  of  a  river  or 
lake  at  which  the  supply  is  derived,  and  from 
which  it  is  conveyed  to  the  waterworks 
pumping  station  for  subsidence  and  filtra- 
tion. The  site  for  the  "  intake  works  "  should 
be  chosen  with  great  care.  At  the  point 
selected  there  should  be  no  tendency  for  the 
river  to  deposit  silt  or  debris  of  any  kind, 
and  for  this  reason  a  convex  bank  or  straight 
reach,  with  suitable  training  works  where 
necessary,  is  preferable.  The  intake  chamber 
should  be  situate  below  the  dry-weather  level 
of  the  river,  so  as  to  exclude  floating  matter, 
but  above  the  bed  of  the  river  to  prevent  silt 
and  deposit  gaining  access.  The  inlet  should 
always  be  protected  by  means  of  a  grating  to 
prevent  any  large  objects  entering.  The 
intermediate  position,  or  level,  of  the  intake 
as  above  enables  water  to  be  drawn  off  in 
cold  climates  between  the  floating  ice  and 
the  ground  or  anchor  ice.  Suitable  means 
for  flushing  out  the  intake  chamber  should 
also  be  provided.  There  are  two  intakes  to 
the  East  London  Waterworks  on  the  river 
Lea — one  at  Ponder's  End  and  the  other 
just  below  the  Ordnance  Factory  at  Enfield. 
Another  intake  connected  with  these  works  is 
situate  on  the  Thames  just  above  the  Sunbury 
Weir  at  Wheatley's  Ait.  It  is  of  paramount 
importance  that  all  water  intakes  from  rivers 
should  be  as  high  up  the  stream  as  practicable, 


242 


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MUNICIPAL   AND   SANITAEY  ENGINEEBING. 


ISO 


above  sewer-outfalls  or  other  discharges  con- 
tributing to  the  pollution  of  the  water. 

Intercepting  Sewer. — (See  "  SEWERAGE.") 

Interceptor. — A  bent  pipe  so  formed  that 
while  liquids  are  permitted  to  flow  through 
it,  air  is  prohibited.  (See  "  DISCONNECTING 
TRAPS.") 

International  Process  of  Sewage  Puri- 
fication.— This  system  of  sewage  purification 
employs  a  magnetic  precipitant  and  deodorizer 
called  "  ferozone,"  and  the  liquid  is  afterwards 
filtered  through  a  "  polar ite  "  filter.  The 
sewage  of  Mangotsfield  is  treated  by  the 
International  Company's  process  with  Candy 
upward  flow  precipitation  tanks,  and  the 
effluent  has  been  very  favourably  reported 
upon.  (See  "POLARITE"  and  "FEROZONE.") 

Inverted  Siphons. — (See  "  SIPHONS.") 

Irrigation,  Broad. — (See  "SEWAGE  DIS- 
POSAL.") 

Isolation  Hospitals. — Acts  of  Parliament 
— Provision  of  Isolation  Hospitals — Local  Govern- 
ment Board  Requirements  as  to  Wards — Porter's 
Lodge  and  Receiving  Blocks  —  Administrative 
Buildings  —  Ward  Pavilions  —  Laundry —  Mor- 
tuary —  Protection  Against  Fire  —  Telephonic 
Installation — Cost  of  Hospitals. — Local  authori- 
ties first  obtained  powers  to  build  or  otherwise 
arrange  for  hospitals  to  deal  with  infectious 
disease  by  the  passing  of  the  Sanitary  Act  of 
1866.  These  powers  were  increased  by  the 
Public  Health  Act,  1875,  and  the  Isolation 
Hospitals  Act,  1893.  In  1883  the  Epidemic 
and  other  Diseases  Prevention  Act  was 
brought  into  force  as  an  amendment  to  the 
Public  Health  Act  (England),  1875.  It  pro- 
vides for  the  prevention  of  any  threatened 
pestilence,  such  as  epidemic,  endemic,  or  in- 
fectious disease,  and  makes  regulations  for 
the  speedy  interment  or  other  disposal  of  the 
dead  ;  house  -  to  -  house  visitation  ;  provision 
of  medical  and  hospital  accommodation ;  and 
also  provides  for  the  cleansing,  ventilation, 


disinfection,  and  the  guarding  against  the 
spread  of  disease.  The  Infectious  Disease 
(Prevention)  Act,  1890,  in  addition  to  other 
matters,  enables  local  authorities  to  make 
free  provision  from  time  to  time  for  tempo- 
rary shelters,  or  house  accommodation,  with 
the  necessary  attendants,  for  the  members 
of  any  family  in  which  an  infectious  disease 
has  appeared,  who  have  been  compelled 
to  leave  their  dwelling  for  the  purpose  of 
enabling  such  building  to  be  disinfected  by 
the  local  authority.  The  Isolation  Hospitals 
Act,  1893,  was  promoted  to  enable  county 
councils  to  establish  hospitals  for  the  recep- 
tion of  patients  suffering  from  infectious 
disease.  This  Act  does  not  extend  to  the  ad- 
ministrative county  of  London,  or  to  any 
county  borough,  or,  without  the  consent  of 
the  council  for  the  borough,  to  any  borough 
containing,  according  to  the  census  for  the 
time  being  in  force,  a  population  of  10,000 
persons  or  upwards,  or  to  any  borough  con- 
taining a  less  population,  -without  the  like 
consent,  unless  the  Local  Government  Board 
by  order  direct  that  the  Act  shall  apply  to  such 
borough.  Under  this  Act  the  council  of  every 
county  may,  on  such  application  being  made 
to  them  and  proof  adduced,  provide  or  cause 
to  be  provided  a  hospital  for  the  reception 
of  patients  suffering  from  infectious  diseases. 
An  application  to  a  county  council  for  the 
establishment  of  an  isolation  hospital  may  be 
made  by  any  one  or  more  of  the  authorities 
having  jurisdiction  in  the  county,  or  any  part 
of  the  county.  Such  an  application  may  be 
made  in  pursuance  of  a  resolution  passed  at 
a  meeting  of  any  authority  by  a  majority  of 
the  members  assembled  thereat,  and  voting 
in  a  manner  in  which  votes  are  required  by 
law  to  be  given  at  a  meeting  of  the  authority. 
An  application  for  the  establ'shment  of  an 
isolation  hospital  may  also  be  made  by  any 
number  of  ratepayers  not  less  than  25.  Such 
application  shall  be  made  by  petition,  and 
shall  state  the  district  for  which  the  isola- 
tion hospital  is  required,  and  the  reasons 
which  the  petitioners  adduce  for  its  estab- 
lishment. In  1899  an  Act  was  passed  to 

R  2 


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ENCYCLOPEDIA  OF 


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extend  the  Infectious  Disease  (Notification)  Act     and  be  well  isolated.     In  towns  wards  should 


to  districts  in  which  it  has  not  hitherto  been 
adopted.  It  extends  to  and  takes  effect  in 
every  urban,  rural,  and  port  sanitary  district. 
This  Act  provides  that  the  head  of  the  family, 
or  the  nearest  relative  of  the  patient  resident 
in  the  building,  must  give  immediate  notice 
(in  case  of  infectious  disease)  to  the  Medical 
Officer  of  Health  ;  that  the  medical  practi- 
tioner attending  the  patient,  on  finding  a  case 
of  infectious  disease,  must  notify  to  the 
Medical  Officer  of  Health  for  the  district  the 
name  of  the  patient,  the  situation  of  the  house, 
and  the  infectious  disease  from  which  the 
patient  is  suffering.  The  Isolation  Hospitals 
Act,  1901,  which  is  an  amendment  of  the 
Isolation  Hospitals  Act,  1893,  provides  that 
any  local  authority  (including  a  joint  board) 
within  the  meaning  of  the  Public  Health  Act, 
1875,  which  has  provided  under  this  Act,  or 
any  local  Act,  a  hospital  for  the  reception  of 
the  sick,  may,  with  the  sanction  of  the  Local 
Government  Board,  and  with  the  consent  of 
the  council,  transfer  it  to  the  council  of  the 
county  within  which  the  hospital  or  any  part 
of  the  district  of  the  authority  is  situate. 
Any  hospital  transferred  under  this  section 
shall  be  appropriated  to  a  district  formed 
under  the  Isolation  Hospitals  Act,  1893,  and 
may  be  adopted  as  an  isolation  hospital ;  and 
any  hospital  so  appropriated  shall  be  treated 
as  if  it  had  been  originally  established  under 
the  Act  for  the  district.  Any  expenses  in- 
curred by  a  county  council  in  or  incidental 
to  the  transfer  of  any  hospital  under  this  Act 
shall  be  defrayed  as  structural  expenses  in- 
curred by  a  hospital  committee  within  the 
meaning  of  section  17  of  the  principal  Act. 

PROVISION  OF  ISOLATION  HOSPITALS. — Hos- 
pital accommodation  for  infectious  and  con- 
tagious diseases  is  required  more  particularly 
in  towns  than  in  rural  districts  ;  still  some 
provision  should  be  made  for  the  most  isolated 
villages.  The  best  arrangement  for  small 
populations  is  by  the  provision  of  a  hospital 
accessible  from  several  villages.  Such  a 
building  could  be  planned  with  accommoda- 
tion for  four  or  more  cases  of  infectious  disease, 


be  placed  in  one  or  more  pavilions,  with  space 
enough  for  the  erection  of  other  blocks, 
temporary  or  permanent.  In  all  hospitals 
there  must  be  a  division  between  the  hospitals 
coining  within  the  category  of  so-called  fever 
hospitals.  They  may  be  divided  into  two 
classes :  those  of  the  sanatoria  type,  pure  and 
simple,  and  those  of  the  hospital  type.  In 
all  cases  it  is  necessary  that  small-pox  cases 
should  be  separated  from  scarlet-fever  and 
diphtheria  patients.  In  the  case  of  infectious 
hospitals  the  ratio  is  about  twenty  beds  for  a 
population  of  25,000.  In  twenty-seven  im- 
portant towns,  having  a  population  of 
nearly  4,500,000,  there  are  twenty  infectious 
beds  to  each  29,000  persons.  At  the  present 
time  London  has  about  10,216  beds  in  the 
hospitals  of  the  Metropolitan  Asylums  Board. 
Some  authorities  advocate  accommodation  for 
infectious  cases  in  the  proportion  of  ten  beds 
per  10,000  of  population,  with  arrangements 
to  admit  of  three  different  infections  in  both 
sexes.  It  is  well  to  provide  an  average  number 
of  two  or  three  simultaneous  infections,  and 
this  should  be  supplanted  by  temporary 
arrangements  in  case  of  necessity.  When 
authorities  contemplate  the  erection  of  a 
hospital  for  small-pox  it  may  be  laid  down, 
with  a  view  to  lessening  the  risk  of  infection, 
that  the  erection  of  the  hospital  should  not 
be  on  a  site  where  it  would  have  within 
a  quarter  of  a  mile  of  it  as  a  centre  either  a 
hospital,  whether  for  infectious  disease  or  not, 
or  a  workhouse,  or  any  similar  establishment, 
or  a  population  of  150  to  200  persons ;  or 
upon  any  site  where  it  would  have  within 
half  a  mile  of  it  as  a  centre  a  population  of 
500  to  600  persons,  whether  in  one  or  more 
institutions  or  in  dwelling-houses.  It  should 
be  understood  that  even  when  the  above  con- 
ditions are  strictly  fulfilled,  there  may  be 
circumstances  under  which  the  erection  of  a 
small-pox  hospital  should  not  be  contemplated. 
Cases  in  which  there  is  any  considerable 
collection  of  inhabitants  just  beyond  the  half- 
mile  zone  should  always  call  for  special  con- 
sideration. The  site  of  a  hospital  should,  if 


244 


ISO 


MUNICIPAL   AND   SANITAEY  ENGINEEKING. 


ISO 


possible,  be  in  the  open  country,  and  so 
maintain  a  maximum  amount  of  purity  of 
air  being  breathed  by  the  patients.  Pre- 
suming that  the  situation  is  unfettered,  except 
by  hygienic  requirements,  the  qualities  of  a 
site  more  favourable  to  an  isolation  hospital 
is  a  clean,  porous,  and  dry  soil,  with  free 
circulation  of  air  round  it. 

LOCAL  GOVERNMENT  BOARD'S  REQUIREMENTS 
AS  TO  WARDS. — The  Local  Government  Board, 
in  their  memorandum  of  requirements  and 
suggestions  relating  to  the  provision  for 
infectious  disease  cases,  state  that  "  any 
building  intended  to  contain  infected  persons 
or  things  should  be  placed  at  least  at  a  dis- 
tance of  40  ft.  from  the  boundary  of  the 
site."  The  following  minimum  amount  of 
space  per  patient  should  be  provided  in  wards 
for  infectious  cases  : — 

Wall  space,  per  bed.         .     12  ft. 
Floor  space      .         .         .     144  sq.  ft. 
Cubic  space      .         .         .     2,000  cu.  ft. 

In  designing  isolation  hospitals  it  will  be 
found  that  if  the  above  amount  of  floor  area 
is  to  be  adhered  to,  then  the  requisite  cubic 
space  can  only  be  obtained  by  adopting  a 
height  of  some  14  ft.  As  this  height  is  some- 
what excessive  in  other  than  wards  of  great 
length,  it  is  desirable  that  a  height  of.  say, 
12  ft.  or  13  ft.  should  be  adopted,  and  the 
floor  space  be  correspondingly  increased.  The 
following  table  gives  the  requisite  space,  and 
at  the  same  time  provides  a  ward  more  suited 
for  supervision : — 

Wall  space,  per  bed.         .     12  ft. 

Height  of  ward        .         .     13  ft. 

Floor  space      .         .         .     156  sq.  ft. 

Cubic  do.          .         .         .     2,028  cu.  ft. 

PORTER'S  LODGE  AND  RECEIVING  BLOCKS. — 
The  entrance  to  a  fever  hospital  should  be  so 
situated  as  to  allow  for  the  separate  admission 
and  discharge  of  patients,  and  also  for  the 
delivery  of  stores  and  for  tradesmen  to  trans- 
act their  business  without  coming  in  contact 
with  the  infected  parts  of  the  hospital.  In 
the  case  of  small  isolation  hospitals  one 
entrance  should  suffice  for  all  purposes.  In 


the  case  of  large  hospitals,  however,  it  is 
desirable  that  the  porter's  lodge  should  be  so 
situated  as  to  allow  of  the  provision  of  two 
entrances,  one  for  infected  to  enter,  and  with 
a  carriage  drive  direct  to  the  hospital  build- 
ings, and  another  for  non-infected,  with  a 
roadway  leading  to  the  administrative  build- 
ings. The  porter's  lodge  usually  comprises 
an  office  and  waiting-room,  sitting-room, 
kitchen,  and  the  usual  out-offices  on  the 
ground  floor,  with  at  least  two  bedrooms  and 
a  bath-room  on  the  first  floor.  In  some  cases 
the  rooms  for  receiving  and  discharging 
patients  are  provided  in  connection  with  this 
building.  When  this  provision  is  provided 
in  a  distinct  block,  the  receiving  apartment 
should  comprise  a  room  for  the  medical  officer 
to  examine  the  patient,  patients'  clothes  store, 
and  bath-room.  The  discharge  block  should 
comprise  an  undressing  room,  where  the 
patient  is  relieved  of  the  hospital  clothing 
and  then  bathed.  Adjoining  the  undressing- 
room,  and  dividing  the  discharge  room,  should 
be  placed  a  bath-room,  "in  order  that  the 
patient,  after  bathing,  may  receive  his  own 
clothes  and  pass  into  the  discharge-room, 
which  should  also  act  as  a  waiting-room  for 
relatives  or'  friends  of  the  patient.  In  some 
hospitals  two  receiving  and  discharge  blocks 
are  provided,  one  for  scarlet  fever,  the  other 
for  diphtheria  and  enteric  fever. 

ADMINISTRATIVE  BUILDINGS. — The  admini- 
strative buildings  should  provide  accommoda- 
tion for  medical  and  nursing  staff,  stores, 
cooking,  &c.  In  small  isolation  hospitals 
provision  is  made  for  matron's  quarters,  nurses' 
sitting-  and  mess-room,  medical  officer's  room, 
dispensary,  mending-room,  stores,  and  the 
necessary  sleeping  accommodation  for  the 
staff.  In  large  hospitals  the  medical  super- 
intendent is  provided  with  a  residence 
separated  from  the  other  buildings.  The 
kitchen  and  stores  should  be  placed  centrally 
to  allow  of  easy  distribution  of  food  and 
stores.  The  matron's  department,  which 
comprises  linen  stores,  needle-room,  and  the 
like  apartments,  should  also  be  placed  in  the 
central  administrative  block.  In  the  case  of 


245 


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ENCYCLOPAEDIA   OF 


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small  isolation  hospitals  the  nurses'  depart- 
ments will  also  be  provided  in  the  adminis- 
trative building.  When,  however,  there  is 
a  large  staff  of  nurses,  as  in  the  case  of 
large  hospitals,  they  are  housed  in  a  separate 
and  distinct  building.  When  a  nurses'  home 
is  provided  it  should  contain  mess-rooms, 
general  sitting-room  or  common  room,  reading- 
room,  and  bedrooms.  The  bedrooms  should 
measure  13  ft.  by  8  ft.  6  in.,  or  12  ft.  by  9  ft. 
The  whole  of  the  rooms  should  be  heated  by 
radiators  ;  fireplaces  should  not  be  provided 
in  the  bedrooms,  as  they  are  rarely  used. 
Provision  should  be  made  for  at  least  one 
sick-room  for  use  as  occasion  may  require. 
Water-closets,  lavatories,  slop-sinks,  and 
baths  should  be  provided  on  each  floor  in 
proportion  to  the  number  of  beds.  Suitable 
provision  should  be  made  in  large  hospitals 
for  medical  students  undertaking  a  course  of 
studies.  In  this  case  a  well-lighted  and 
ventilated  lecture-room  should  be  provided 
in  connection  with  the  administrative  build- 
ings. When  provision  is  made  for  housing 
students,  they  should  be  accommodated  in  a 
block  quite  distinct  from  the  other  buildings. 
WARD  PAVILIONS.  —  In  considering  the 
number  of  beds  apportioned  to  each  disease, 
it  should  be  borne  in  mind  that  scarlet  fever 
demands  almost  a  half  of  the  total  bed 
accommodation.  As  scarlet  fever  is,  in  the 
large  majority  of  cases,  an  acute  disease 
during  the  first  one  or  two  weeks  only,  and 
seeing  that  it  is  generally  admitted  to  be 
most  desirable  to  separate  these  cases  from 
convalescents,  the  best  arrangement  is  to  have 
two  separate  blocks — a  small  one  for  acute 
cases  and  a  large  one  for  convalescents.  The 
small  pavilion  should  have  a  couple  of  one- 
or  two-bed  wards  for  the  isolation  of  delirious 
and  noisy  cases.  The  separation  wards  should 
be  provided  with  separate  and  distinct  water- 
closet  and  slop-sink.  The  walls  and  ceilings 
of  all  wards  should  be  finished  with  a  plaster 
or  cement  face,  and  be  painted  or  varnished. 
The  angles  made  by  the  walls  with  each  other 
and  with  the  ceiling  should  be  finished  with 
quadrant  shaving  the  concave  surface  to  the 


ward.  The  whole  of  the  ceilings  should  be 
quite  plain,  free  from  all  projections,  angles,  or 
cornices  which  accumulate  dust.  The  floors 
of  all  wards  should  be  constructed  of  such 
material  as  will  be  capable  of  being  easily 
cleaned.  Wood  as  a  material  for  floors  in 
wards  is  far  from  satisfactory,  being  full  of 
joints,  which  frequently  open  and  become 
receptacles  for  impurities.  The  best  material 
for  floors  is  terrazzo,  or  one  of  the  many 
jointless  floors  now  in  general  use.  The 
latter  are  preferable,  being  much  warmer. 
The  windows,  where  the  cost  will  allow  of  it, 
should  be  double-glazed  to  prevent  the  loss 
of  heat  and  to  maintain  an  even  temperature 
in  the  ward.  They  should  have  an  area  of 
not  less  than  1  ft.  of  glass  for  every  70  cu.  ft. 
of  ward  space.  A  window  should  be  arranged 
between  each  pair  of  beds,  and  it  is  advisable 
to  place  a  window  in  each  corner  of  the  ward, 
between  the  end  wall  and  the  last  bed.  The 
windows  should  be  divided  into  two  parts,  of 
which  the  upper  part  is  made  to  fall  in  and 
form  a  hopper  ventilator,  glazed  hoppers 
being  fixed  on  each  side ;  the  lower  portion 
being  formed  as  double-hung  sashes.  The 
doors  in  the  wards  should  be  so  arranged  as 
to  facilitate  nursing,  and  be  large  enough  to 
allow  the  passage  through  of  the  sick  on 
movable  stretchers.  The  doors  should  afford 
an  opening  of  from  3  ft.  8  in.  to  4  ft.  The 
construction  of  all  doors  in  wards  should  be 
such  as  to  present  as  few  projections  or  places 
for  the  accumulation  of  dust  as  possible.  The 
upper  part  of  entrance  doors  to  wards  should 
be  glazed.  The  ward  adjuncts  for  water- 
closets,  slop  and  scalding  sinks  should  be 
separated  from  the  wards  by  intervening 
lobbies,  having  windows  at  each  side.  It  is 
advisable  to  fix  in  each  of  these  lobbies  a 
radiator  capable  of  raising  the  temperature  to 
a  higher  degree  than  that  of  the  ward,  so  that 
the  air  is  drawn  from  the  ward  into  the  lobby 
instead  of  vice  versa.  In  the  disconnecting 
lobby  between  the  wards  and  water-closet  and 
slop-sink  two  openings  should  be  formed  in 
the  external  walls,  one  for  the  reception  of 
soiled  linen  (which  can  be  drawn  through  by 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


ISO 


the  attendant  on  to  a  trolley  outside),  and  a 
smaller  opening  in  which  stools  can  be  kept 
for  inspection.     It  is  necessary  to  fix  a  tightly- 
fitting   internal  iron    door   to  each  of  these 
openings.     A   nurses'   duty   room  should  be 
provided  in  connection  with  each  large  ward  ; 
it  should  lead  direct  from  the  corridor  and 
be  so  situated  as  to  overlook  both  the  principal 
and  the  separation  wards.     It  should  contain 
a    gas    cooking-stove,    dresser,    washing   and 
rinsing  sink,  and  a  small  cupboard.    Provision 
should  also  be  made  in  each   pavilion  of  a 
water-closet,  lavatory,  and  a  robing-room  for 
the  use  of  the  staff.     It  is  advisable  to  pro- 
vide open  fireplaces  in  all  wards  in  addition 
to  the  heating  by  hot-water  pipes  and  radiators. 
In   the   case   of   large   wards   down  draught 
stoves  should  be  provided,  fixed  in  the  centre 
of  the  wards.     Suitable  provision  should  also 
be  made  for  the  admission  of  fresh  air  and 
the    extraction    of   vitiated  air.     (See  "  VEN- 
TILATION.") 

THE  LAUNDRY. — The  laundry,  which  is  one 
of  the  most  important  departments  of  an 
isolation  hospital,  should  be  so  situated  as  to 
allow  of  the  receiving  and  dispatch  of  linen 
without  any  undue  distance  being  traversed. 
This  building  should,  however,  be  well  removed 
from  the  ward  pavilions  and  the  adminis- 
trative buildings.  The  laundry  should  con- 
tain two  departments,  one  for  the  staff  and 
the  other  for  the  patients'  washing.  Adjoining 
the  patients'  washhouse  provision  should  be 
made  of  a  foul-washhouse  for  receiving  and 
steeping  articles  soiled  by  excreta.  It  should 
be  fitted  with  tanks  classified  for  scarlet  fever, 
enteric  fever,  diphtheria  and  isolated  cases. 
The  laundry  proper  should  comprise  a  wash- 
house,  drying  apartment,  ironing  rooms  and 
receiving  and  delivery  rooms. 

Provision  is  necessary  for  disinfecting  all 
clothing  of  the  patients,  bedding,  &c.,  from 
the  wards.  The  disinfecting  chamber  should 
adjoin  the  laundry  and  be  fitted  with  a  steam 
disinfector.  The  disinfecting  apartment  com- 
prises two  chambers,  one  for  receiving  the 
infected  clothing  and  the  other  for  receiving 
the  clothes  after  they  have  passed  through 


the  disinfector.  There  should  be  no  com- 
munication between  the  two  chambers.  (See 
"  LAUNDRIES.") 

It  is  also  necessary  to  make  provision  for 
the  destruction  of  all  refuse,  which  frequently 
consists  of  mattresses  and  bedding  on  which 
patients  have  been  lying,  bandages,  portions 
of  food,  ordinary  sweepings,  and  solid  and 
liquid  excrement.  This  building  is  best  placed 
so  as  to  adjoin  the  laundry. 

MORTUARY. — Every  hospital  should  be  pro- 
vided with  a  mortuary,  which  should  have 
facilities  for  isolating  bodies  for  the  purpose 
of  viewing  and  identification.  The  mortuary 
should  comprise  a  room  fitted  with  slabs  for 
the  reception  of  dead  bodies,  visitors'  waiting- 
room,  and  viewing  closet.  A  post-mortem 
room  should  adjoin  the  mortuary  and  have  a 
north  light.  This  room  should  be  well  lighted 
and  ventilated  and  furnished  with  sinks,  lava- 
tory, anatomical  table,  and  glass  shelves  for 
the  storage  of  bottles.  The  whole  of  the  walls 
should  be  faced  with  glazed  bricks  or  glazed 
tiles,  and  the  floor  covered  with  terrazzo 
paving. 

PROTECTION  AGAINST  FIRE. — Where  buildings 
are  of  two  or  more  storeys  in  height  they 
should  be  provided  with  external  fire-escape 
staircases  for  use  in  cases  of  emergency. 
Suitable  provision  of  fire  appliances  is  also 
necessary  to  protect  the  buildings  against  fire, 
and  the  most  ready  means  should  always  be 
at  hand  with  which  to  attack  a  fire  at  its  out- 
break. Fire  hydrants  fitted  with  hose  and 
hand  pipes  should  be  fixed  in  every  building, 
and,  in  addition,  fire  buckets  should  be  pro- 
vided as  an  extra  precaution. 

TELEPHONIC  INSTALLATION. — A  system  of 
electric  intercommunication  should  be  pro- 
vided between  every  part  of  an  institution, 
either  by  means  of  telephones  or  bells.  Tele- 
phonic communication  between  each  of 
the  ward  pavilions  and  the  administrative 
buildings  is  also  necessary  for  cases  of  emer- 
gency. A  bell-call  should  also  be  provided 
from  the  medical  superintendent's  and  the 
matron's  office  to  the  porter's  lodge  and  the 
nurses'  home ;  also  from  the  stores,  laundry 


247 


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and  porter's  lodge ;  a  signal  code  in  reference 
to  the  supply  of  steam,  outbreak  of  fire,  or 
other  call,  being  previously  arranged. 

COST  OF  HOSPITALS. — The  cost  of  erecting 


Discharge  _Pipe 
'For  EFFIuent- 


Kessel  Separator. 

hospitals  for  infectious  disease  has  been  found 
to  vary  considerably.  The  average  cost  of 
the  Metropolitan  Asylums  Board's  Hospitals, 
which  provide  accommodation  for  some  500 
beds  in  each  institution,  is  about  £450  per 
bed.  The  cost  of  isolation  hospitals  in  the 
provinces  is  found  to  be  from  £500  down  to 
£272  per  bed ;  as  an  example  Baguley, 


Cheshire,  cost  £512  per  bed  ;  Burnley  £486  ; 
Coventry  £308^  ;  Liverpool  £456^,  while  the 
Bridlington  isolation  hospital  cost  only  £272 
per  bed.  A.  C.  F. 


"  Ives  "    Tank.  —  The 

"  Ives "  upward-flow  self- 
acting  continuous  precipi- 
tating tank  of  the  Universal 
Sewage  Purification  Co.  was 
introduced  by  Mr.  Ives  in 
1894  and  1895,  and  has 
been  installed  by  several 
authorities.  It  is  somewhat 
complicated  in  design,  is 
circular  in  plan,  and  in- 
cludes arrangements  for 
aeration.  As  a  preliminary 
preparation,  the  centrifugal 
reduction  of  the  coarser 
solids  by  whirling  them 
against  bafflers  is  employed, 
by  which  they  are  broken 
up  and  brought  into  suspen- 
sion for  subsequent  chemical 
treatment.  The  precipitant 
used  in  connection  with  this 
tank  is  Spence's  alumino- 
ferric  in  the  form  of  slabs 
of  suitable  size,  and  the 
tank  effluent  is  passed  over 
land,  or  through  coke  or  ash 
filter  beds. 


Kessel    Separator.— 

This  is  a  boiler-shaped 
apparatus  first  introduced 
in  Germany  with  the  object 
of  the  economical  removal 
of  suspended  matters  from 
It  consists  of  an  elongated  vertical 
cylinder  having  an  inverted  cone-shaped 
bottom  and  a  domed  top  as  illustrated  in  the 
figure.  The  vessel  is  erected  on  iron  or  brick 
supports  over  the  line  of  sewer,  and  the  flow 
of  sewage  is  siphoned  through  the  cylinder 
at  such  a  rate  as  will  permit  of  the  deposition 
of  solids,  the  liquid  portion  being  discharged 


Inlet  Manhole 


248 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


LAT 


with  a  loss  of  head  of  about  3  in.  only  in  the 
level  of  the  sewer.  From  the  figure  it  will  be 
seen  that  the  inlet  or  short-leg  of  the  siphon 
takes  its  sewage  from  a  small  manhole  and 
discharges  within  the  vessel  at  a  point  verti- 
cally over  a  central  deposit  pipe  into  which  the 
coarser  solids  are  deflected.  As  indicated  by 
the  arrows,  the  sewage  liquid  rises  and  enters 
a  narrow  annular  slot  around  an  internal 
inverted-cone,  the  lower  portion  of  which 
connects  with  a  discharge  or  effluent  pipe 
(forming  the  long-leg  of  the  siphon)  which, 
passing  downwards  through  the  lower  part  of 
the  Kessel,  terminates  by  means  of  a  trapped 
end  in  a  second  manhole.  The  end  of  the 
long-leg  is  made  about  3  in.  lower  than 
the  level  of  the  inlet  or  short-leg  so  as  to 
ensure  the  necessary  siphonic  action  upon 
which  the  motion  of  the  sewage  through  the 
Kessel  depends.  Needless  to  say  the  whole 
apparatus  must  be  made  and  kept  perfectly 
air-tight  throughout,  and  accumulations  of  air 
from  the  sewage  or  elsewhere  in  the  top  of 
the  vessel  would  interfere  with  its  proper 
action.  A  further  pipe  is  also  provided  from 
the  apex  of  the  cone,  as  shown  in  the  illustra- 
tion, for  the  discharge  of  gas  and  fat.  To 
start  siphonic  action  through  the  Kessel  it 
is  necessary,  as  in  the  case  of  any  other 
siphon,  to  first  fill  the  apparatus  with  water 
and  then  simultaneously  open  the  valves  on 
the  legs. 

The  size  of  Kessel  for  any  given  case  depends 
greatly  upon  the  nature  of  the  sewage,  but  the 
capacity  must  be  large  enough  to  give  a 
sufficiently  slow  speed  of  flow  to  permit  of  the 
deposition  of  the  solids.  A  cylinder  8  ft.  in 
diameter  will  deal  with  from  2,000  to  4,000 
gallons  per  hour,  and  one  of  30  ft.  diameter 
from  25,000  to  50,000  gallons  per  hour.  For 
physical  reasons  the  height  of  the  vessel  must 
not  exceed  the  limit  of  the  atmospheric 
pressure  as  compared  with  the  specific  gravity 
of  the  sewage,  or  say,  from  27  to  30  ft.  It 
is  stated  that  with  ordinary  domestic  sewage 
about  70  %  of  the  solids  in  suspension  are 
removed. 

The  Kessel  is  not  at  present  in  use  in  this 


country,  but  there  are  a  number  of  such  plants 
at  work  in  Germany  and  others  in  course  of 
erection.  The  design  of  a  Kessel  to  meet  any 
particular  case  naturally  depends  upon  the 
class  of  sewage  to  be  dealt  with  and  the  rate 
at  which  its  suspended  solids  are  found  to 
precipitate,  but,  broadly  speaking,  it  is  claimed 
equally  thorough  precipitation  of  solids  can  be 
secured  in  either  the  Kessel  or  in  the  "  Com- 
min- Separator"  (see  "COMMIN- SEPARATOR")  at 
half  the  cost  of  septic  or  ordinary  sedimentation 
tanks. 

Lateral  Water  Filtration.  — A  combina- 
tion of  the  lateral  and  downward  flow  of  water 
through  filter  beds  has  been  adopted  in  order 
to  secure  rapidity  of  action  and  economy  of 
construction  and  maintenance.  This  principle 
is  embodied  in  the  McGregor  system,  which 
has  been  introduced  in  Canada.  Bound  a 
sunken  circular  pure  water  reservoir  a  number 
of  concentric  filter  beds  are  built,  each  ring 
from  the  centre  outwards  being  stepped  on  a 
higher  level,  the  base  of  the  outer  ring  being 
on  a  level  with  the  top  of  the  inner  bed.  The 
number  of  the  concentric  rings,  their  width 
and  depth,  and  the  composition  of  the  bed 
may  be  varied  according  to  the  amount  of 
water  required,  the  quality  of  the  water  and 
the  degree  of  purity  to  be  arrived  at.  The 
bases  of  the  beds  have  a  slight  inward  slope, 
and  at  the  base  of  the  inner  walls  are  open- 
ings— protected  with  metal  screens  fitting  in 
iron  gratings.  The  inner  bed  has,  in  addition 
to  these  screens,  duplex  wire  strainers,  through 
which  the  filtered  water  flows  into  the  reser- 
voir. The  beds  are  divided  into  sections  by 
means  of  partition  walls,  so  that  one  or  more 
sections  can  be  put  out  of  action  for  cleansing 
or  repairs  without  interrupting  filtration. 
The  crude  water  is  sprinkled  over  the  top, 
and  outer,  bed,  and  flows  downwards  and 
sideways,  from  bed  to  bed.  The  stresses  on 
such  beds  are  very  slight  and  evenly  dis- 
tributed. Armoured  concrete  may  be  used  for 
their  construction,  and  the  reservoirs  and  beds 
may  be  protected  from  the  action  of  sun  and 
frost  by  a  roof. 


249 


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LAU 


Laundries. — These  establishments  fall  into 
two  main  divisions  :  (1)  those  equipped  for 
hand  labour  ;  (2)  those  wherein  machinery  is 
driven  by  mechanical  power.  Each  of  these 
divisions  is,  for  purposes  of  consideration, 
divided  into  four  classes  : — 

(a)  Private  laundries. 

(b)  Trading  laundries. 

(c)  Baths  and  wash-houses  laundries. 

(d)  Public  institutions  laundries. 

(1)  HAND  LAUNDRIES  are  found  chiefly  in 
connection  with  private  houses  and  certain 
descriptions  of  public  institutions,  such  as 
schools,  workhouses,  lunatic  asylums.  For 
some  years  the  tendency  has  been  for  the 
genuine  trading  hand  laundry  to  disappear,  and 
the  new  Factory  and  Workshop  Act,  1907— 
amending  the  Factory  and  Workshop  Act,  1901 
(referred  to  as  "  the  Principal  Act  ") — has 
hastened  this  desirable  consummation.  The 
sanitary  requirements  in  hand  laundries  neces- 
sitate the  provision  of  good  ventilation,  lighting, 
drainage,  and  an  adequate  supply  of  fairly  soft 
water.  (See  "  WATER  SOFTENING.")  There 
should  be  at  least  two  rooms  ;  the  wash-house 
and  the  ironing  and  packing  room.  A  drying 
closet  may  be  built  into  one  corner  of  the 
ironing  room,  or  the  iron  heating  stove  may 
be  screened  off  so  as  to  form  a  drying  closet ; 
but  in  such  an  establishment  a  built-in  brick 
closet  is  best.  This  should  be  in  two  divisions 
each  of  them  having  a  door.  Between  the 
divisions  there  should  be  a  kind  of  cell  to 
contain  an  iron  heating  stove,  and  there 
should  be  direct  communication  between  this 
heating  chamber  and  the  closet  by  means  of 
hot  air  flues,  provided  with  dampers.  The 
heat  can  then  be  directed  into  or  shut  off 
from  one  or  both  of  the  divisions  as  desired. 
In  this  way  it  is  possible  to  economise  heat, 
and,  at  the  same  time,  afford  workers  the 
necessary  protection  from  radiation.  When 
one  section  of  the  closet  is  being  loaded,  or 
unloaded,  heat  is  shut  off  and  the  door  opened. 
In  large  establishments  it  may  be  necessary 
to  provide  more  heat  than  that  produced  by 
the  above  method.  This  can  be  obtained  by 
placing  a  small  furnace  beneath  the  closet, 


or  by  providing  hot  air  or  steam  radiators. 
The  floors  should  be  impermeable,  and  for 
the  wash-house,  concrete,  floated  with  good 
cement,  is  best,  as  it  is  easy  with  this  material 
to  arrange  for  a  slight  inclination  towards  a 
gutter,  placed  centrally  or  against  the  lateral 
walls,  and  communicating  with  a  trapped  drain. 
The  plant  usually  consists  of  steeping  tanks 
and  washing  troughs.  These  should  be 
either  of  hard  wood  or  salt-glazed  stoneware. 
Rotary  washing-machines  and  hydro-extrac- 
tors are  now  made  for  driving  by  hand-power 
(see  below). 

(2)  POWER  LAUNDRIES  are  equipped  with 
machines  which  are  generally  worked  by 
steam-engines,  although  gas-engines  and 
hydraulic  and  electric  motors  are  also  used. 

(a)  PRIVATE  LAUNDRIES  should  contain  not 
less  than  two  rooms,  (1)  wash-house,  fitted  with 
washing    troughs,     steam-driven     washing- 
machines,      wringer     or     hydro-extractors  ; 
(2)  ironing  and  packing  room.     This  last  may 
be  fitted  with  strong  tables  for  hand  ironing, 
or  with  ironing  machines.     A  good  plan  is  to 
place  the  drying  closet  between  the  two  rooms, 
with  a  door  opening  into   each,  so  that  the 
wet  linen  may   be  inserted  from   the  wash- 
house  side,  and  when  dry  may  be  removed  by 
the  other  door.     The  floor  of  the  wash-house 
must  be  smooth  and  impermeable.     In  small 
laundries,  induced  draught  will  be    sufficient 
for  ventilation  ;  there  should  be  inlet  grids 
with  air-filtering  boxes  near  the  ground,  and 
outlet  grids,   preferably  communicating  with 
vaned  cowls  in  the  roof.     The  latter  should 
Ite  near  the  chimney  stack,  as  the  heat  thus 
gained  will  become  the  accelerator  of  circula- 
tion of  air. 

(b)  TRADING     LAUNDRIES.  —  An     essential 
point  in  all  large  laundries  is  that  the  estab- 
lishment should  be  planned  so  that  the  soiled 
linen    enters   at   one   door,  and   after   being 
counted  and  sorted,  passes  on  to  be  steeped, 
washed,   rinsed,  dried,  starched,   ironed,  and 
packed,  and  so  out  at  another  door.    We  must, 
therefore,  have  not  less  than  four  main  rooms, 
preferably  on  the  ground  floor,  with  engine 
and  boiler-house  attached,  and  ample  sanitary 


250 


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LAU 


accommodation  near,  but  having  no  direct 
communication  with  any  of  the  working 
rooms.  The  first  room  is  the  receiving 
department,  where  the  linen  is  counted  and 
sorted,  table,  bed,  body,  and  kitchen  articles 
forming  different  heaps  to  be  treated  separ- 
ately. This  room  being  the  most  exposed  to 
contamination  should  be  fitted  as  plainly  as 
possible  to  facilitate  cleansing.  The  wash- 
house  should  come  next,  and  communicate 
either  by  means  of  a  corridor,  or  a  trap-door 
in  the  partition  wall,  with  the  receiving 
department.  The  wash-house  must  be  well 
lighted,  either  by  means  of  sky-lights  or 
windows  placed  rather  high  up.  The  walls 
must  be  smooth,  white-washed  at  the  upper 
part,  but  having  a  dado  6  ft.  high,  painted 
in  oil  colour.  The  floor  should  be  of  concrete 
with  a  coating  of  cement,  and  given  a  slight 
inclination  towards  a  draining  gutter,  placed 
either  down  the  middle  of  the  room  or 
against  the  walls,  such  gutters  being  protected 
by  iron  grids,  and  connected  with  trapped 
drains.  In  order  to  economise  power,  the 
heavy  rotary  washing  machines  and  hydro- 
extractors  should  be  placed  as  near  the  ironing 
room  partition  as  possible,  as  this  will  simplify 
the  planning  of  the  shafting  for  transmission 
of  power,  reduce  its  extent,  and  lessen  the 
length  of  belting.  It  is  a  good  plan  to  run 
both  washing  and  ironing  machines  from  one 
main  shafting,  as  this  not  only  economises 
material  and  power,  but  the  pulling  from  right 
to  left  tends  to  equalise  the  strain  and  so  con- 
duces to  smooth  running.  Against  the 
opposite  wall  there  should  be  large  steeping 
tanks  of  either  galvanized  iron  or  salt-glazed 
stoneware,  and  washing  troughs  of  hard  wood 
or  stoneware. 

Tanks  and  troughs  should  be  fitted  with 
cold  and  hot  water  (or  steam)  service  pipes 
and  taps,  and  large  waste  valves.  The  wastes 
of  tanks  and  troughs,  and  also  of  all  machines, 
should  discharge  through  a  free  opening  over 
the  drain,  not  directly  into  it ;  by  this  means 
the  dangers  of  siphonage  (of  water  or  gases) 
are  prevented,  and  stoppages  arising  from 
articles  being  dropped  through  are  avoided. 


On  reaching  the  wash-house,  all  very  soiled 
linen     (body,    bed,    and   kitchen    chiefly)    is 
steeped  in  the  tanks.     If  the  fouling  is  of  an 
organic  nature  (blood  or  excreta),  cold  or  luke- 
warm water,  with  a  very  little  soda  should  be 
used  to  soften,  but  prevent  coagulation.   After 
steeping,  the  articles  are  generally  treated  by 
hand  in  the  washing  troughs  to  remove  stains, 
and   are   then    passed    on    to    the    washing 
machines.     There  are  a  large  variety  of  wash- 
ing machines,  but  those  most  commonly  used 
are   of    the  rotary   type,    and  consist  of   an 
outer  stationary  cylinder  and  an  inner  revol- 
ving  cage.       Both    cylinder    and    cage    are 
provided   with  doors,  and   may  be   made   of 
wood  or  metal,    or   the  cylinder  may  be    of 
metal,  and  the  cage  of  wood,  or  vice  versa. 
The  outer  casing  should  be  fairly  solid,  and 
fitted  with   hot  and  cold   water  taps,   steam 
valve,   water   gauge,   large    outlet    or   waste 
valve,  and  fast  and  loose  pulleys  for  the  trans- 
mission of  power,  with  starting  and  stopping 
gear.     The  cage  is  made  either  of  rods  placed 
close  together,  or  of  perforated  sections,  so  as 
to   admit   water    freely.       The   rods   or   the 
sections  may  be  so  arranged  as  to  present  an 
internal   corrugated    surface,    or    "  rubbers " 
may  be  provided.     In  many  cases,  a  series  of 
metal  tubes  or  a  rounded  slat  of  hard  wood, 
are  placed  like  a  mid-feather  to  act  as  lifters. 
When  the  linen  is  packed  in  these  cages,  the 
doors  are  closed,  hot  water  is  admitted  and 
dissolved   soap    and    soda   added   through   a 
hopper.     The  water  may  be  brought  to  the 
boil   by   admitting   steam.      The  machine  is 
then  set  in  motion  by  bringing  the  driving 
belt  from  the  fast  to  the  loose  pulley.     Then 
the  cage  revolves,  rolling  over  the  linen,  carry- 
ing   it   half    up    the    revolving    circle,   and 
allowing  it  to  fall  back   into  the  soap  suds ; 
meanwhile  a  rain  of  soapy  water  falls  through 
the   perforations.     In   many   machines,  this 
action  is   increased   by  providing  horizontal 
bands  of  metal  or  wood  on  the  outer  periphery 
of  the  cylinder,  which  act    like  cups,  lifting 
the  water  which  descends  through  the  perfora- 
tions.    Were  the  cage  to  revolve  only  in  one 
direction,   the   linen   would  not  be   properly 


251 


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ENCYCLOPEDIA  OF 


LAU 


cleansed,  as  it  would  soon  be  formed  into  a 
tight  ball,  so  the  revolution  of  the  cage  is 
automatically  reversed  at  every  five  or  six 
revolutions.  The  cleansing  action  of  such 
machines  consists  of  a  series  of  motions, 
combining  rubbing,  rolling,  and  squeezing, 
meanwhile  forcing  the  water  through  the  fabric. 
Without  stopping  the  machine,  the  soapy 
water  can  be  emptied  by  opening  the  waste 
valve ;  then  hot  water  can  be  admitted  for  the 
first  rinse,  followed  by  rinses  in  warm,  and 
finally  in  cold  water.  After  this,  blueing 
fluid  may  be  introduced.  Handling  is  thus 
reduced  to  a  minimum,  and  all  operations 
made  as  automatic  as  possible.  After  washing 
and  rinsing,  the  linen  may  be  passed  through 
wringers  or  placed  in  hydro-extractors.  The 
hydro-extractor  consists  of  a  strong  outer 
casing  and  an  inner  perforated  basket,  which 
is  made  to  revolve  in  an  upright  position. 
The  wet  linen  is  packed  in  the  basket,  which 
is  then  set  in  motion  and  driven  at  a  high 
speed  (from  800  to  1,500  revolutions  per 
minute),  the  centrifugal  force  expelling  the 
water,  which,  escaping  through  the  perfora- 
tions, is  drained  off.  From  the  wringers 
or  hydro-extractors  the  linen  may  be  either 
starched  (by  hand  or  machinery),  or  may  pass 
direct  to  the  drying  closets.  These  may  con- 
sist of  rooms  heated  by  means  of  waste  gases 
from  stoves,  or  by  steam  passing  through 
radiator  coils,  or  the  room  may  be  fitted  with 
a  series  of  draw-out  horses  on  which  the 
linen  is  hung.  If  an  ordinary  drying  room 
is  used,  it  should  be  in  duplicate,  as  the  closet 
has  to  be  cooled  down  before  the  attendant 
enters  to  hang  up  or  remove  the  linen.  From 
the  drying  closets  the  articles  pass  on  to  the 
ironing  room.  Here  small  articles  and  finery 
are  ironed  by  hand,  but  most  of  the  linen 
handled  is  dealt  with  on  elaborate  machinery. 
Bed  and  table  linen  is  generally  treated  on 
large  machines  of  the  "  Decoudun  "  or  multi- 
ple roller  types.  The  "Decoudun"  machine 
consists  of  a  concave  steam  chest,  forming  on 
the  top  a  polished  metal  bed,  on  which  a 
large  hollow  roller,  covered  with  flannel, 
and  sheeting  rests.  Steam  is  admitted  into 


the  bed  at  a  high  pressure,  and  consequently 
a  pressure-gauge  and  safety-valve  are 
necessary.  The  linen  is  placed  on  the  lip  of 
the  bed  and  the  revolving  roller  guides  it 
gently  through,  drying  and  polishing  it  as  it 
goes.  Two  or  more  passages  are  necessary. 
In  the  multiple  roller  machines,  the  steam 
heated  bed  has  two,  three,  or  more  depres- 
sions, in  which  flannel  covered  rollers  revolve. 
In  such  machines  the  heating  surface  is  larger 
and  the  action  more  rapid.  A  large  variety 
of  more  or  less  complicated  machines  are  now 
made  for  ironing  shirts  and  collars  and  cuffs, 
for  goffering,  and  so  on.  From  the  ironing 
room  the  linen  passes  to  the  despatch  depart- 
ment, where  it  is  inspected,  checked,  and 
packed.  It  will  be  seen  that  a  well  ordered 
laundry  offers  considerable  safeguards  to 
health,  as  the  linen  is  handled  as  little  as 
possible,  the  soiled  being  kept  away  from  the 
clean ;  it  is,  moreover,  subjected  to  the  action 
of  soap  and  steam.  The  ventilation  of  such 
an  establishment  must  be  efficient,  and  this 
can  rarely  be  attained  by  any  "  natural  " 
system  of  inlets  and  outlets,  even  if  the  out- 
lets be  heated.  Mechanical  propulsion  or 
extraction  is  necessary.  This  is  usually 
accomplished  by  means  of  fans  placed  high 
up  in  the  walls  or  the  roof,  in  an  opening 
communicating  with  the  interior  and  exterior 
of  the  building.  These  fans  may  be  placed 
so  that  they  extract  vitiated  air  and  steam 
from  all  departments.  In  large  establish- 
ments where  the  extraction  is  considerable,  it 
may  be  necessary  to  regulate  the  introduction 
of  fresh  air,  which  is  usually  drawn  into  a 
cleansing  and  warming  chamber  by  means 
of  a  suction  fan,  and  then  blown  through  air 
conduits,  provided  with  regulator  inlet  grids 
in  each  room. 

(c)  Laundries  attached  to  public  baths  and 
wash-houses  (q.v.)  are  now  often  elaborately 
fitted  up. 

(cl)  PUBLIC  INSTITUTION  LAUNDRIES  should 
be  planned  on  the  same  principle  as  trading 
establishments,  to  secure  a  regular  circuit, 
the  clean  linen  being  kept  apart  from  the 
soiled,  once  it  has  left  the  wash-house. 


252 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


LAV 


Whenever  possible  all  departments  should  be 
on  the  ground  floor,  whether  in  a  separate 
building  with  top-lights,  or,  as  is  often  done, 
in  the  basement.  Only  in  the  latter  case 
special  attention  must  be  paid  to  ventilation, 
and  artificial  lighting  becomes  necessary. 
Unless  the  laundry  is  at  some  distance  from  the 
institution,  the  corridors  near  dormitories 
may  be  connected  with  the  receiving  room  by 
means  of  shutes,  so  that  the  soiled  linen  can 
be  removed  to  the  laundry  rapidly  without 
difficulty.  Such  shutes  must  be  smooth  and 
impermeable  to  permit  of  periodical  flushings, 
and  provided  at  the  corridor  end  with  tight- 
fitting  doors.  Linen  from  infectious  diseases 
wards  is  placed  in  galvanized  iron  bins 
containing  some  disinfecting  fluid,  and  is 
then  removed  to  the  wash-house.  After 
steeping  for  a  prescribed  number  of  hours, 
the  linen  is  removed  and  washed  separately. 
After  the  first  soap  wash  (or  breakdown),  the 
second  soap  suds  are  boiled  during  the  process 
of  washing  by  means  of  the  admission  of 
steam  under  pressure.  The  liquid  from  the 
disinfecting  bins  and  the  washing  machines 
used  for  infected  linen,  or  linen  soiled  with 
blood  and  excreta,  should  be  run  into  a  special 
steam-tight  tank,  built  beneath  the  floor,  and 
boiled  for  some  minutes  by  the  admission  of 
steam,  then  allowed  to  cool  before  being 
discharged  into  the  sewer.  The  washing 
machines  for  this  class  of  laundry  are  usually 
of  a  heavy  type  with  strong  doors,  as  much 
steam  is  used,  both  to  facilitate  cleaning  and 
as  a  bactericide.  Foul  rotary-washing 
machines  are  made  to  deal  with  soiled  body 
and  bed  linen.  This  machine  consists  of  a 
single  cylinder,  of  heavy  metal,  hung  hori- 
zontally in  bearings  supported  by  standards. 
A  casing  of  splash-boards  is  provided,  partly 
enclosing  the  lower  section  of  the  cylinder. 
The  cylinder  has  a  steam-tight  door,  and  also 
a  large  orifice  protected  by  a  grid  and  a  screw- 
down  cap.  The  foul  linen  having  been  placed 
in  the  machine,  the  door  is  fastened  close 
and  the  cap  unscrewed  ;  then  cold  water  is 
admitted  and  the  machine  set  in  motion. 
Plenty  of  water  must  be  used  to  soften  and 


remove  dirt,  which  is  carried  away  by  the 
rush  of  water  as  the  cylinder  revolves.  After 
a  few  minutes  hot  and  cold  water  is  run 
together,  then  the  machine  is  stopped,  the 
cap  screwed  down,  and  soap  and  water 
admitted,  the  regular  processes  of  washing, 
boiling,  and  rinsing  being  pursued.  Such 
machines,  like  the  ordinary  rotaries  used  for 
treating  infected  linen,  should  have  two-way 
waste  cocks,  so  that  the  water  may  be  dis- 
charged either  into  the  disinfecting  tank  or 
direct  into  the  sewer.  In  institution  laundries 
the  wash-house  and  drying  closets  are  rela- 
tively of  more  importance  than  the  ironing 
room,  thus  differing  from  a  trading  establish- 
ment. In  school,  workhouse,  and  asylum 
laundries,  where  inmates  often  take  a  share 
in  the  work,  special  precautions  must  be 
observed  in  fencing  machines  and  providing 
safety  guards,  protecting  all  working  parts. 

Lavatory  Basins. — Now  almost  exclu- 
sively made  of  white  glazed  earthenware. 
There  are  three  types  :  (a)  Tip-up  lavatories  ; 
(b)  plug  basins ;  and  (e)  "  Rivulet  "  basins. 
In  the  first-named  the  basins  are  emptied  by 
tipping  their  contents  into  containers  below 
them,  to  which  the  waste  pipes  are  fixed. 
Although  convenient  in  hotels  and  other 
public  places  where  the  basins  are  in  constant 
demand  and  rapid  emptying  therefore  desir- 
able, they  can  hardly  be  regarded  as  sanitary 
in  view  of  the  large  soiling  surfaces  exposed. 
Plug  basins,  which  are  the  most  frequently 
used,  are  made  as  self-contained  fittings,  or 
may  be  fixed  under  marble,  slate,  or  other 
slabs.  In  selecting  them  particular  attention 
should  be  paid  to  the  wTaste  pipes  and  over- 
flows. In  hidden  standing  overflows  in 
which  the  water  contained  by  the  basin  is  in 
contact  with  that  in  the  overflow,  and  in 
basins  in  which  water  enters  through  the 
waste  pipes,  there  is  great  risk  of  carrying 
infection  from  one  user  to  the  next.  The 
spread  of  skin  disease,  there  is  reason  to 
think,  is  greatly  due  to  these  types  of 
appliances,  which  are  frequently  to  be  found 
in  public  places.  Rivulet  basins  are  useful 


253 


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ENCYCLOPAEDIA   OF 


LEA 


in  hospitals,  schools,  &c.  They  are  basins  in 
which  a  depression  is  substituted  for  the 
bowl,  water  flowing  constantly  through  it. 
Although  very  sanitary,  the  hands  being 
washed  in  running  water,  they  tend  to  waste 
water,  and  can  only  be  made  use  of  in  special 
circumstances.  All  basins  should  be  fixed  free 
of  all  enclosure. 

Lead. — The  chief  ore  of  lead  is  galena,  or 
sulphide  of  lead,  which  has  a  crystalline  form 
and  striking  lead-like  lustre.  It  is  smelted 
and  run  into  half-round  troughs  to  form  pigs 
weighing  1  cwt.  each.  Sheet  lead  is  generally 
made  by  casting  a  thick  block  weighing  from 
4  to  6  tons  and  passing  it  under  metal  rollers 


Ram 


Press  for  making  Lead  Pipes. 

until  it  is  reduced  to  the  thickness  required, 
when  it  is  called  milled  lead.  The  sheets  are 
from  24  ft.  to  36  ft.  long,  and  5  ft.  to  8  ft. 
wide,  the  finished  thickness  varying  from 
-^o  in.  to  T3^  in.  thick,  but  they  are  generally 
known  by  the  weight  in  pounds  per  foot 
super.,  say,  3  Ibs.  to  10  Ibs.  In  roof  work 
the  lead  for  aprons,  flashings,  and  soakers  is 
4  Ibs.  or  5  Ibs. ;  for  hips  and  ridges,  5  Ibs.  to 
7  Ibs. ;  for  gutters  and  flats,  or  any  place 
liable  to  be  walked  upon,  6  Ibs.  to  8  Ibs. ;  for 
soil  pipes,  7  Ibs.  or  8  Ibs. ;  for  lining  sinks, 
6  Ibs.  to  8  Ibs.  The  weight  in  pounds  per 
foot  super,  multiplied  by  0'017  will  give  the 
thickness  in  decimals  of  an  inch.  For 
example,  8  Ibs.  lead  is  0'136  in.  thick,  or  a 
trifle  over  £  in.  Lead  pipes  are  made  in  a 
hydraulic  press,  the  principle  of  which  is 
shown  in  the  figure.  Molten  lead,  from  which 


the  scum  has  been  removed,  is  contained  in  a 
steel  cylinder  having  a  rod  standing  up  in 
the  centre  equal  in  diameter  to  the  inside  of 
the  pipe.  A  ram  above  has  a  hole,  or  die, 
equal  in  diameter  to  the  outside  of  the  lead 
pipe  to  be  made.  When  the  lead  has  just  set, 
either  the  cylinder  is  forced  upwards  or  the 
ram  is  forced  downwards  by  hydraulic  pres- 
sure and  the  lead  is  squirted  through  the 
annular  space  between  the  die  and  the  rod,  to 
form  a  continuous  pipe  which  is  wound  on  a 
wooden  drum.  The  following  are  the  average 
weights  of  lead  pipe,  but  great  variation 
occurs  :  for  instance,  Farmiloe  &  Sons  manu- 
facture eleven  thicknesses  of  f  in.  pipe  alone  : 


Bore  in  Inches. 

Average  weight  in  Ibs.  per  yard. 

Common. 

Middling. 

Strong. 

\ 
¥ 
1 

3-20 

4-80 
6-00 

4-40 
5-60 
8-00 

5-20 
7-20 
920 

it 

9-00 
12-00 

11-00 
14-00 

18-25 
17-50 

2 

16-80 

21-00 

24-90 

2* 

21-00 

26-80 

30-00 

Lead  pipes  are  sold  in  lengths  as  follows:  \  in. 
to  1  in.,  in  15  ft.  lengths  or  coils  of  60  ft. ; 
\\  in.  to  2  in.,  in  12  ft.  lengths  and  some  of 
them  in  coils  of  36  ft.  Lead  pipes  must  not 
be  used  for  conveying  soft  water,  as  the 
oxygen  of  the  air  contained  in  small  quantities 
in  the  water  acts  upon  the  lead,  converting  a 
portion  into  oxide  of  lead  which  is  very  poison- 
ous and  accumulates  in  the  human  system. 
Hard  water  does  not  have  the  same  effect,  as 
some  of  the  carbonates  contained  are  deposited 
on  the  lead  and  protect  it.  H.  A. 

Leaping  Weirs. — Leaping  or  separating 
weirs  were  introduced  by  Mr.  J.  F.  Bateman, 
F.E.S.,  on  the  Manchester  Waterworks,  and 
are  now  very  generally  adopted  in  various 
forms  for  the  purpose  of  causing  turbid  and 
impure  flood  waters  to  be  automatically 
rejected  whilst  the  pure  normal  flow  falls 
into  a  clear  water  conduit  below  the  weir. 


254 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


LEV 


CLEAR  WATER 
CONDUIT 


For  example,  when  a  mountain  stream  crosses 
an  aqueduct  the  clear  ordinary  flow  may  be 
admitted   to    such   aqueduct  and   the   turbid 
flood  flow  rejected  by  constructing  a  weir  (as 
illustrated)  across  the  stream.     It  will  be  seen 
that   the  increased   velocity    of    the 
water  when   the    stream    is    swollen 
and  discoloured  in   flood  will  cause 
it   to    leap    over    the    comparatively 
narrow    slot,    giving    access    to    the 
clear  water  conduit  below,  and  flow 
down    the    stream    to    the   river    or 
compensation    reservoir   at   a   lower 
level.     In  the  simplest  forms  of  this 
device  the  width  of  the  slot  or  open- 
ing    is     fixed     once     for     all     by 
experiment,  but  circumstances  some- 
times require  that  it  should  be  made  adjust- 
able or  capable   of   being   entirely    closed  if 
required.       Different    forms    will    be    found 
illustrated    in    the    catalogues  of   makers    of 
waterworks  apparatus. 

Levelling,    General    Principles    of.— 

Levelling  is  usually  performed  by  means  of  a 
"  dumpy "    level    consisting   essentially   of   a 
spirit  level  combined  with  a  small  telescope, 
which,    to    save  light,   is  fitted  with  a  non- 
erecting  eye-piece,  so  that  objects  viewed  by  it 
appear  upside  down ;  the  optical  axis  of  the 
telescope  is  adjusted  to  be,  truly  horizontal 
when  the  bubble  of  the  spirit  level  is  in  the 
centre  of  its  run.     There  is  also  a  small  cross 
level  by  which  the  telescope  may  be  levelled  at 
right  angles  to  its  axis.      Between  the  object 
glass  and  the  eye-piece  is  placed  a  diaphragm, 
generally  consisting  of  a  glass  plate  with  one 
central  horizontal  and  two  parallel  vertical 
lines  engraved  upon  it ;    these  lines    become 
visible  in  the  field  of  view  when  the  instrument 
is  in  focus.     The  telescope  is  mounted  upon 
a  tripod  stand  and  can  be    turned   about  a 
vertical  axis  ;  the  perpendicularity  of  this  axis 
can  be  adjusted  by  milled  screws,  of  which 
there  are  three  or  four,  but  preferably  three,  in 
order  that  the  level  may  be  made  to  revolve 
in  a  truly  horizontal  plane. 

The  other  important   instrument   used  in 


levelling  is  the  staff.  This  is  made  in  three 
pieces,  the  two  upper  portions  sliding  tele- 
scopically  within  the  lower  and  fastening  by 
spring  catches  ;  the  height  of  the  staff,  when 
extended,  is  generally  14  ft.  The  face  of  the 


Leaping  Weir. 

staff  is  painted  in  divisions  of  a  foot,  and  also 
in  tentbs  and  hundredths  of  a  foot — the  feet 
are  coloured  red,  the  tenths  black,  and  the 
hundredths  are  indicated  by  alternate  lines 
and  spaces. 

In  using  a  level  it  must  be  so  adjusted  that 
the  bubble  remains  in  the  centre  of  its  run  in 
whatever  position  the  telescope  is  turned.  To 
set  up  a  three-screw  or  "tribach  "  instrument, 
the  tripod  is  firmly  planted  and  the  telescope 
placed  in  a  line  with  two  of  the  screws  wrhich 
are  adjusted  until  the  bubble  in  the  large  tube 
comes  to  the  centre ;  then,  without  moving  the 
telescope,  the  bubble  of  the  cross  level  is 
brought  to  the  centre  by  manipulating  the  third 
screw.  This  last  process  may  slightly  upset 
the  first  and  render  readjustment  necessary  ; 
after  this,  the  telescope  should  be  rotated  to 
prove  the  adjustment  all  round,  and  any  final 
correction  made  with  tbe  large  spirit  level. 

In  setting  up  a  four-screw  level,  the  telescope 
is  placed  as  level  as  possible  and  in  line  with 
two  of  the  legs,  and  is  first  adjusted  by  the  two 
screws  which  are  parallel  to  it;  it  is  then 
turned  at  right  angles  and  adjusted  in  this 
direction  by  the  other  pair  of  screws,  the 
process  being  repeated  until  the  bubble 
remains  stationary  in  whatever  direction  the 
telescope  is  pointed.  The  eye-piece  must  be 
focussed  until  the  cross  hairs  or  lines  appear 
perfectly  distinct  in  the  field  of  view,  and  any 


255 


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ENCYCLOPEDIA   OF 


LEV 


distant  object,  such  as  the  figuring  on  the 
staff,  sharply  and  steadily  defined.  The  first 
adjustment  is  essential  whenever  the  level  is 
shifted,  and  the  second  if  the  distance  from 
the  staff  is  altered  ;  others  are  occasionally 
required,  but  these  two  comprise  all  that  is 
necessary  when  the  level  is  in  perfect  order. 

The  staff  must  be  held  perfectly  upright  by 
an  assistant  so  that  its  image  may  appear 
between  the  two  vertical  lines  in  the  field  of 
view  ;  the  upper  edge  of  the  horizontal  line  is 
the  point  at  which  all  readings  are  taken. 

The  operation  of  levelling  may  now  be  con- 
sidered. In  a  few  words  this  consists  in 
determining  the  variation  in  elevation  of 
different  points  on  the  earth's  surface  from  an 
assumed  level  line.  Owing  to  the  shape  of 
the  earth  a  truly  level  line  would  be  a  curve 
with  its  extremities  equidistant  from  the  earth's 
centre,  whereas  the  line  of  "  apparent  "  level, 
as  set  out  by  an  instrument,  would  be  tangen- 
tial to  the  former  line,  and  its  divergence  will 
be  equal  to  the  square  of  its  length  divided  by 
the  radius  of  the  earth — both  expressed  in  the 
same  units ;  thus,  at  1  mile  the  apparent 
level  will  be  8'007  in.  above  the  true  level, 
at  2  miles  it  will  be  32*028  in.,  and  so  on. 

Terrestrial  refraction  is  another  source  of 
error  ;  it  is  generally  about  one-seventh  of  the 
amount  due  to  curvature. 

As  refraction  causes  objects  to  appear  higher 
than  they  really  are  it  reduces  the  correction 
required  for  curvature,  so  that  the  allowance 
for  both  will  be  represented  by  the  difference. 
Although  these  corrections  have  in  some  cases 
to  be  made,  in  practical  work  the  error  can 
generally  be  neutralised  by  placing  the  level 
midway  between  the  sighting  stations. 

The  actual  work  of  levelling  is  governed  by 
the  following  rule  : — 

"Less  staff "  =  a  rise  in  ground;  "More 
staff"  =  a  fall. 

To  take  a  case  of  simple  levelling ;  suppose 
it  is  required  to  find  the  difference  of  level 
between  two  points  A  and  B.  The  level  is 
set  up  about  midway  between  the  two  and 
sighted  upon  the  staff  when  standing  upon  the 
point  A  (we  will  suppose  the  reading  to  be 


9'34  ft.)  ;  the  staff  is  then  transferred  to  point 
B,  the  level  turned  round  and  a  reading  taken, 
which  we  will  assume  to  be  6'25  ft.  B  is 
obviously  3'09  ft.  higher  than  A.  It  is  almost 
superfluous  to  add  that  the  height  of  the 
telescope  makes  no  difference  whatever. 

COMPOUND  LEVELLING  consists  of  a  series  of 
observations  by  which  the  undulations  of  the 
ground  may  be  determined  for  any  required 
distance.  We  will  assume  that  it  is  necessary 
to  take  a  line  of  levels  through  five  points, 
A,  B,  C,  D,  and  E.  The  level  is  set  up,  as 
before,  between  A  and  B  and  sighted  on  to  the 
staff  at  A — this  is  called  a  "  back  "  sight ;  it 
is  then  turned  round  and  "  fore  "  sighted  on 
to  B,  both  readings  being  noted  in  a  special 


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"  level "  note  book.  After  entering,  each  read- 
ing should  be  taken  over  again  as  a  check.  The 
staff  is  then  carefully  turned  round  to  face 
point  C,  the  level  shifted  and  set  up  between 
C  and  D,  and  "  back  "  and  "  fore"  sights  again 
taken  and  duly  booked ;  the  process  is  repeated 


256 


LEV 


MUNICIPAL    AND    SANITAEY   ENGINEERING. 


LIG 


through  the  series.  In  ordinary  work  "  inter- 
mediate "  readings  are  taken,  to  do  which  the 
staff  only  is  shifted  ;  thus,  if  the  distance  from 
A  to  C  was  not  more  than,  say,  250  ft.,  one 
might  read  from  the  level  to  B  and  again  to  C  ; 
in  this  case  B  would  be  an  intermediate  sight. 
A  specimen  of  the  bookings,  writh  suppositious 
figures,  is  here  given. 

By  starting  at  a  given  "datum  "  point  and 
working  back  again  to  it,  the  accuracy  of  the 
levels  may  be  checked  ;  or,  if  the  line  be  started 
on  a  Government  "bench"  mark  (a  broad 
arrow)  ascertained  from  an  ordnance  survey 
sheet,  and  finished  on  another,  a  check  is 
afforded  ;  this  has  been  assumed  above,  where 
it  will  be  seen  that  the  total  fall  (6'69  —  T09) 
agrees  with  the  difference  in  level  of  the  bench 
marks. 

DATUM  LINE. — All  levels  are  estimated  with 
reference  to  a  horizontal  line,  such  as  the 
ordnance  "datum"  (in  Great  Britain,  the 
mean  level  of  the  sea  at  Liverpool),  or  any 
other  altitude  that  may  be  convenient.  In 
the  above  case  of  supposed  levelling,  point  A 
is  obviously  142'20  ft.  above  ordnance  datum. 
To  plot  a  line  of  levels,  or  "  section,"  on  paper, 
the  datum  is  first  drawn  and  the  horizontal 
distances  marked  off  to  a  convenient  scale  ;  the 
vertical  lines  are  then  erected  from  these 
points  and  the  reduced  levels  are  pricked 
thereon  (for  convenience  of  measurement  a 
large  scale  is  here  adopted).  The  points  are 
connected  by  a  line  which  represents  the 
surface  of  the  ground. 

Levelling  may  also  be  performed  with  the 
theodolite.  (See  "  SURVEYING,  GENERAL  PRIN- 
CIPLES OF.") 

Altitude  may  also  be  approximately  deter- 
mined by  means  of  an  aneroid  barometer 
which  indicates  difference  of  level  by 
registering  the  variation  in  atmospheric 
pressure. 

The  well-known  principle  that  the  boiling 
point  of  water  varies  with  the  atmospheric 
pressure,  and  therefore  the  altitude,  is  made 
use  of  in  an  instrument  known  as  the 
"  Hypsometer,"  which  consists  of  a  small  boiler 
heated  by  a  spirit  lamp  and  fitted  with  a 


thermometer.     This  apparatus  is  sometimes 
employed  as  a  check  to  the  aneroid. 

E.  L.  B. 

Liernur  Process  of  Sewage  Removal 
and  Disposal. — The  Liernur  process  pro- 
vides for  the  pneumatic  removal  and  disposal 
by  evaporation  of  the  sewage  of  towns.  The 
area  to  be  drained  is  divided  into  districts, 
each  provided  with  a  "  district  reservoir," 
from  which  the  sewage  is  pneumatically 
extracted  and  conveyed  through  3^-in.  and 
4-in.  iron  pipes  to  a  receiving  reservoir 
at  the  central  station  by  means  of  a 
vacuum  pump  maintaining  a  vacuum  not 
exceeding  half  an  atmosphere.  The  system  is 
in  use  at  Trouville,  where,  it  is  stated,  the 
sewage  is  stored  in  a  covered  tank  for  about  a 
week,  mixed  with  sulphuric  acid  for  the 
purpose  of  fixing  the  ammonia,  heated  in 
tubular  boilers  to  120°  C.,  evaporated  to 
a  semi-solid  state,  and  then  reduced  in  a 
rotary  chamber  to  a  dry  .powder,  the  value  of 
which  is  put  at  from  £7  to  £8.  The  process 
is  worked  by  the  Liernur  Company  at  Trouville 
at  an  average  annual  charge  of  16s.  per  house. 
The  system  was  first  applied  at  Amsterdam 
in  1871,  and  has  been  introduced  at  Leyden, 
Riga,  and  other  places,  including,  more 
recently,  Stansted  in  Essex. 

Lighting. — (See  "ACETYLENE,"  "ELEC- 
TRICITY," and  "  GAS.") 

Lightning-Conductors. — Lightning  is  the 
sudden  dissipation  of  electrical  energy  which 
has  been  stored  between  a  thunder-cloud  and 
the  earth,  or  between  one  cloud  and  another, 
with  a  considerable  difference  of  potential.  It 
makes  its  own  path,  and  forces  its  way 
through  obstacles  without  regard  to  their 
electrical  resistance.  The  function  of  a 
lightning-conductor  is  not  so  much  to  furnish 
a  path  for  the  flashes  of  lightning  when  they 
occur,  as  to  dissipate  the  electrical  energy  as 
fast  as  it  is  generated,  and  thus  prevent  it 
from  accumulating  in  dangerous  quantities. 
With  this  in  view  a  conductor  should  terminate 


257 


LIG 


ENCYCLOPAEDIA  OF 


LIM 


in  a  series  of  points  to  which  the  electricity 
may  be  attracted.  The  falling  drops  in  a 
shower  of  rain  also  help  to  dissipate  accumu- 
lations of  electricity. 

Where  a  great  difference  of  potential  exists 
between  two  clouds,  culminating  in  an 
electrical  discharge  from  one  to  the  other,  the 
charge  in  the  lower  cloud  is  liable  to  over- 
flow suddenly  to  the  earth,  causing  the  so- 
called  "B  flash,"  against  which  lightning- 
rods  afford  little  or  no  protection.  It  used 
to  be  considered  that  each  lightning-rod 
formed  the  centre  of  a  "  protected  cone," 
having  a  diameter  at  its  base  equal  to  the 
height  of  the  rod,  or  even  greater.  Sir  Oliver 
Lodge,  however,  is  of  opinion  that  there  is  no 
space  near  a  rod  which  can  be  definitely  styled 
an  area  of  protection.  A  single  rod  does  not 
afford  adequate  protection  even  for  a  chimney 
shaft,  and  a  building  can  only  be  rendered 
absolutely  safe  from  lightning  by  enclosing  it 
in  a  network  of  wires  like  a  birdcage.  For 
practical  purposes  a  reasonable  degree  of 
safety  may  be  secured  by  placing  two  or  more 
rods  in  suitable  positions,  and  joining  them 
by  a  horizontal  conductor,  to  which  any 
exposed  metal -work  and  all  prominently 
projecting  parts  of  the  building  should  be 
connected.  From  an  electrical  point  of  view 
iron  is  preferable  to  copper  as  a  material  for 
lightning-rods,  the  high  conductivity  of  the 
latter  being  positively  objectionable.  Owing, 
however,  to  the  rapidity  with  which  iron 
oxidises,  copper  should  be  used  for  rods  placed 
in  inaccessible  positions.  A  main  conductor 
of  iron  should  be  built  up  of  stout  galvanized 
wire,  and  should  weigh  not  less  than  2£  Ibs. 
per  foot.  A  copper  rod  may  consist  either 
of  tape  or  rope,  and  should  weigh  not  less 
than  6  oz.  per  foot. 

For  subsidiary  conductors  smaller  sections 
may  be  used.  All  joints  should  be  as  perfect 
as  possible,  both  electrically  and  mechanically. 
The  rods  should  not  be  insulated  from  the 
building,  but  should  be  secured  by  metal 
holdfasts.  They  should  be  arranged  as  far  as 
possible  in  straight  lines,  sharp  bends  being 
highly  dangerous.  The  foot  of  each  rod  should 


have  a  good  earth  connection  in  permanently 
damp  soil.  This  may  take  the  form  either 
of  a  metal  plate  not  less  than  3  ft.  square, 
or  of  a  spike  driven  deep  into  the  ground. 
All  metal  stove  pipes  should  be  connected  to 
earth,  as  should  also  the  columns  of  a 
steel-frame  building.  Cases  of  damage  to  a 
modem  steel-frame  structure  are  practically 
unknown. 

The  question  of  lightning-conductors  was 
investigated  by  the  "  Lightning-Rod  Con- 
ference "  (1878 — 1881),  and  again  by  the 
"Lightning  Research  Committee"  (1901 — 
1905),  who  formulated  a  set  of  rules  for 
guidance  in  the  protection  of  buildings. 

A.  J.  M. 

Lime  and  Sulphate  of  Iron  (Treatment 
of  Sewage). — For  the  disposal  of  the  Metro- 
politan sewage  at  Barking  and  Crossness,  lime 
and  sulphate  of  iron  have  been  used  as 
precipitants  in  tanks  on  the  continuous  flow 
principle  for  many  years.  Four  grains  of 
lime  to  one  of  sulphate  of  iron  per  gallon  of 
sewage  are  the  proportions  used.  An  excess 
of  lime  is  detrimental  to  the  effluent  as 
a  portion  of  the  suspended  matters  are 
rendered  soluble  thereby.  (See  "  LONDON 
MAIN  DRAINAGE.") 

Lime  Process  (Treatment  of  Sewage).— 

Following  the  employment  of  Clark's  process 
for  treating  water  supplies,  lime  has  been 
largely  used  as  a  precipitant  for  sewage,  either 
alone  or  in  conjunction  with  other  materials. 
The  purest  lime,  such  as  from  the  upper  chalk 
or  limestones  of  Derbyshire,  should  be  used.  It 
is  added  to  the  sewage  in  a  perfectly  caustic 
state  in  the  proportion  of  12  grains  per 
gallon  after  a  preliminary  screening  of  the 
sewage.  For  the  best  results  the  lime  should 
be  in  solution,  and  to  this  end  it  is  first 
slaked  with  water  and  ground  in  a  mortar  mill 
or  lime  mixer  to  a  finely  divided  or  creamy 
condition.  It  is  then  thoroughly  incorporated 
with  the  sewage  by  means  of  mechanical 
agitators,  and  the  mixture  allowed  to  settle 
for  an  hour,  or  longer  if  possible.  Where 


258 


LIM 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


LIM 


the  quantity  of  sewage  is  large,  however, 
the  precipitating  tanks  are  worked  on 
the  continuous  principle.  The  resulting 
sludge,  which  is  considerable  in  quantity,  is 
periodically  swept  out  of  the  tanks  into  sludge 
wells,  and  from  thence  pumped,  gravitated,  or 
otherwise  conveyed  to  sludge  lagoons  to  dry 
more  or  less,  so  that  it  may  be  employed  as 
manure  on  land,  or  disposed  of  according  to 
local  circumstances.  Sometimes  it  is  pumped 
direct  on  to  land,  and  steam-ploughed  in,  which 
is  the  most  satisfactory  method,  as  otherwise 
putrefaction  soon  sets  in  and  gives  rise  to 
nuisance.  Where  no  more  economical  means 
are  available,  it  becomes  necessary  to  reduce 
the  bulk  of  the  sludge  by  pressing  out  the 
water  in  sludge  presses,  but  this  costs  about 
2s.  per  ton  of  pressed  sludge  cake.  The  cost 
of  the  lime  process  is  about  Sd.  per  head 
of  the  population  per  annum.  The  method  is 
in  use  at  Wolverhampton,  Willesden,  Bury, 
Leyton,  and  many  other  places.  The  resulting 
effluent  is  alkaline,  and  a  secondary  decom- 
position sets  in  when  discharged  into  rivers  ; 
the  effluent  is  also  destructive  to  fish  life. 

Lime.  —  Pure  lime  consists  of  a  com- 
bination of  the  gas  oxygen  with  the  metal 
calcium  forming  an  oxide  of  calcium,  but 
neither  calcium  nor  lime  occurs  in  a  natural 
state.  The  various  limes  of  commerce  are 
obtained  by  burning  limestone,  marble,  chalk, 
or  other  substances,  consisting  chiefly  of  car- 
bonate of  lime,  the  carbon  dioxide  and 
moisture  being  driven  off  by  the  heat,  causing 
a  loss  of  weight  of  about  one-half.  There  are 
various  forms  of  lime,  but  the  commonest  are 
chalk  lime,  grey  lime,  and  lias  lime. 

CHALK  LIME  is  known  as  a  fat  or  rich  lime 
because  it  will  bear  the  admixture  of  a  large 
quantity  of  sand.  When  freshly  burnt  in  the 
form  of  lump  lime  it  will  absorb  a  large 
quantity  of  water,  disengage  great  heat,  and 
swell  into  a  bulky  powder  of  hydrate  of  lime  : 
this  is  the  process  of  slaking.  When  mixed 
with  sand  and  more  water  it  is  used  for 
plastering,  but  not  for  mortar.  It  sets  slowly  by 
the  evaporation  of  moisture,  and  hardens  more 
slowly  by  the  re-absorption  of  carbon  dioxide 


259 


from  the  air.  It  will  not  set  in  a  damp 
situation,  and  is  unsuitable  for  mortar,  as  it 
has  so  little  ultimate  strength. 

GREY  LIME,  or  stone  lime,  obtained  by 
burning  limestone  or  the  lower  chalk,  is  a 
"poor"  lime,  that  is,  it  will  not  bear  much 
sand  added,  owing  to  the  greater  proportion  of 
inert  matter  contained,  say  10  %  to  30  °/0,  but 
it  is  a  slightly  hydraulic  lime,  because  some  of 
the  impurity  is  clay,  which  gives  it,  when 
burnt,  the  property  of  setting  in  a  damp 
situation.  This  lime  slakes  more  sluggishly 
and  with  less  disengagement  of  heat,  but  it 
sets  more  quickly  and  attains  greater  ultimate 
strength  and  hardness.  It  is  used  for  mortar, 
say  one  part  lime  to  two  or  three  parts 
sand,  but  should  not  be  used  for  plastering 
owing  to  the  tendency  to  "  blow  "  from  the 
delayed  slaking  of  certain  hard  -  burnt 
particles. 

LIAS  LIME  is  produced  by  burning  the  lime- 
stone from  the  lyas  beds  at  Lyme  Regis, 
Rugby,  Bath,  Aberthaw,  &c.  Owing  to  a 
large  proportion  of  clay  in  its  composition  the 
lime  produced  is  generally  very  hydraulic,  and 
will  even  set  under  water.  It  takes  a  long 
time  to  slake,  and  should  be  ground  either 
immediately  after  burning  or  while  being  made 
into  mortar  in  a  mortar  mill.  It  makes  good 
concrete  in  substitution  for  Portland  cement, 
and  is  largely  used  for  mortar  for  engineering 
works.  It  sets  quicker  than  other  varieties  of 
lime  and  is  much  stronger. 

HYDEATED  LIME. — Lime  in  its  dryhydrated 
form,  or  slaked  with  just  sufficient  water  for 
the  purpose,  is  now  becoming  a  marketable 
product  in  America.  The  advantages  of 
hydrated  lime  are  summed  up  as  follows  : — 
"  Since  it  exists  as  a  delicate  white  powder, 
and  comes  into  commerce  in  sacks,  it  is 
more  easy  to  handle  and  can  be  more 
accurately  measured  than  the  lump  product. 
The  method  of  handling  this  material  re- 
sembles that  of  cement,  and  it  requires  no 
ageing  after  being  mixed  with  water.  Further, 
it  does  not  deteriorate  rapidly,  and  can  be 
stored  for  a  long  time  in  any  dry  place 
without  undergoing  material  changes,  thus 


s  2 


LOC 


ENCYCLOPEDIA  OF 


LOC 


doing  away  with  the  loss  of  lime  due  to 
spoiling  and  the  danger  of  fire  from  the 
quick-lime  coming  in  contact  with  water." 

H.  A. 

Local    Government    Board    Require- 
ments :  Cemeteries. — The  requirements  of 
the  Local    Government    Board  in   regard  to 
cemeteries  from  the  sanitary  standpoint  can 
best  be  ascertained  by  reference  to  a  memo- 
randum issued  by  the  Board  dated  December 
13th,    1880.     This    memorandum   begins   by 
pointing  out  that  the  Public  Health  (Inter- 
ments) Act,  1879,  provides  for  an  extension  of 
the  powers  of  Sanitary  Authorities  under  the 
Public  Health  Act,  1875,  so  as  to  include  the 
acquisition,  construction,  and  maintenance  of 
"  a  place  for  the  interment  of  the  dead,  in  the 
Act  of  1879  called  a  Cemetery."    It  then  goes 
on  to  say  that  in  cases  where   the   Sanitary 
Authority  propose  to  defray  the  cost  of  estab- 
lishing a  cemetery  by  means  of  a  loan  the 
sanction    of    the   Local    Government    Board 
becomes  necessary  (Public  Health  Act,  1875, 
s.  233).     Among  the  points  considered  by  the 
Board  in  each  particular  case,  before  granting 
their  sanction  to  a  loan  for  the  purpose  of  a 
cemetery,   the    question   as   to   whether   the 
proposed  site  is  suitable  or  unobjectionable 
from  a  sanitary  point  of  view  will  find  a  place. 
The  dangers  to  public  health  which  will  be 
considered  are  set  forth  as   being    the  con- 
tamination   (1)  of   air,    and    (2)  of   drinking- 
water;  and  the  memorandum  then  proceeds 
to  set  forth  the  view  taken  by  the  Board  as  to 
the  hygienic  principles  to  be  observed  in  the 
establishment  of  a  cemetery.     The  memoran- 
dum   above   referred   to   should   be   read   in 
conjunction  with    a    circular    of    the   Local 
Government  Board  dated  August  19th,  1879, 
explanatory  of  the  provisions  of  the  Public 
Health   (Interments)   Act,   1879,   and   also  a 
memorandum  dated  July,  1908,  covering  a  set 
of  model  bye-laws  with  respect  to  the  manage- 
ment of  a  cemetery.     The  Board  also  supply 
a  form  of  queries  to  be  filled  up  and  of  infor- 
mation to  be  furnished   in    connection  with 
applications  by  Burial  Authorities  relative  to 


the  provision  of  new  burial  grounds.  The 
form  sets  out  in  detail  the  various  documents 
which  must  be  forwarded  in  addition  to  the 
answers  to  the  questions  specified.  The 
Board  in  loan  applications  require,  inter  alia, 
particulars  in  Form  K,  No.  2,  as  to  existing 
indebtedness  and  assessable  value  of  the  dis- 
trict ;  and  the  periods  allowable  for  repayment 
of  loans  are  60  years  for  purchase  of  free- 
hold land,  30  years  for  erection  of  buildings, 
and  20  years  for  other  work.  The  memo- 
randum of  July,  1908,  sets  out,  inter  alia, 
the  requirements  of  the  Board  in  regard  to 
space,  which  will  vary  (as  it  is  pointed  out) 
according  to  the  death-rate  of  the  district. 
Taking  average  numbers  in  a  stationary 
population  of  1,000,  there  would  be  19  deaths 
per  annum,  of  which  7  would  be  under  12 
years  of  age.  This,  on  the  basis  of  4  sq.  yds. 
for  an  adult  and  2  for  a  child,  would  mean 
that  62  sq.  yds.  of  ground  is  specified  as 
a  yearly  requirement.  These  are  the  sizes 
recommended  for  grave  spaces  (i.e.,  of  the 
plots  of  ground  each  to  contain  one  grave), 
into  which  the  cemetery  is  to  be  divided. 
On  the  basis  of  paths  occupying  one-sixth  of 
the  available  space,  in  one  acre  4,033  sq.  yds. 
would  be  available  for  grave  spaces ;  and 
this,  assuming  a  single  interment  in  each  grave, 
means  that  an  acre  of  ground  will  serve  a 
population  of  1,000  for  65  years.  Other 
details  are  set  out  somewhat  voluminously, 
indicating  diverse  usages  according  to  the 
nature  of  the  soil,  but  these  can  best  be 
understood  by  studying  the  memorandum 
itself.  W.  M.  F. 

Local  Government  Board  Require- 
ments: Hospitals.— The  control  of  the 
Local  Government  Board  exercisable  over 
local  authorities  in  regard  to  hospitals  arises 
in  several  ways,  but  chiefly  through  the  usual 
medium  of  application  for  the  borrowing  of 
money  by  the  local  authority  which  can  be  pro- 
vided for  by  section  69  of  the  Local  Govern- 
ment Act,  1888,  so  far  as  County  Councils 
are  concerned,  and  by  sections  233  and  234  of 
the  Public  Health  Act,  1875,  so  far  as  other 


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authorities  (extra  metropolitan)  are  concerned, 
whilst  London  itself  has  its  own  Public 
Health  Act,  which  deals  with  the  subject.  In 
regard  to  these  applications,  in  addition  to  the 
usual  particulars  as  to  cost,  plans,  &c.,  the 
Local  Government  Board  generally  requires 
provision  to  be  made  for  the  repayment  of 
any  loans  sanctioned  by  them  for  hospital 
purposes  within  the  following  periods  : — 
Land  purchase  (freehold)  .  .  60  years. 
Buildings  (permanent)  .  30  ,, 

Heating  apparatus         .         .  30      ,, 

Floating  hospital  .         .  30      ,, 

Furniture      .         .         .         .  10      „ 

Ambulances  and  vans    .         .         .     10      ,, 

The  Local  Government  Board  has  from 
time  to  time  issued  memoranda  on  the  subject, 
and  the  most  important  of  these  is  one  dated 
May,  1902  (which  can  be  obtained  from  the 
Government  printers).  It  provides  a  great 
deal  of  useful  and  suggestive  information  as 
to  some  points  which  may  be  taken  to  be 
practically  the  requirements  of  the  Local 
Government  Board  in  regard  to  these  hos- 
pitals. It  has  reference  to  isolation  hospital 
accommodation,  and  it  professes  to  be  issued 
with  a  view  to  indicating  to  local  authorities, 
more  especially  to  those  of  districts  of  small 
or  moderate  size,  the  importance  of  providing 
hospital  accommodation  for  the  isolation  of 
infectious  cases  and  the  means  by  which  they 
may  most  advantageously  make  such  provi- 
sion. The  principles  it  sets  forth  are  said  to 
be  those  which  should  be  kept  in  view  by  all 
local  authorities  who  propose  to  provide  hos- 
pitals for  their  district  by  means  of  loans 
sanctioned  by  the  Local  Government  Board. 
The  memorandum  goes  on  to  deal  with  the 
subject  of  the  area  to  be  served  and  the  size 
of  the  hospital  in  proportion  to  the  population 
of  the  district ;  it  further  deals  with  the 
choice  of  a  site  and  the  erection  of  hospital 
buildings,  and  it  includes  plans  of  different 
types  of  ward-blocks,  with  especial  reference 
to  small-pox  hospitals.  This  memorandum 
gives  in  the  most  accessible  form  the  require- 
ments of  the  Local  Government  Board  as  to 
hospital  schemes.  It  should  be  stated  that  in 


this  memorandum  it  is  pointed  out  that  the 
Local  Government  Board  do  not  as  a  rule 
sanction  loans  for  the  erection  of  iron  hos- 
pitals or  any  hospital  buildings  of  a  temporary 
character,  except  under  special  circumstances. 
With  regard  to  cost  of  hospital  schemes,  some 
observations  are  made  in  the  annual  report 
of  the  Local  Government  Board  for  the  year 
1904—5.  This  is  what  the  Board  say  :— •"  In 
connection  with  the  borrowing  of  money  by 
local  authorities  for  hospital  purposes,  we 
have  found  that  in  many  cases  expenditure — 
sometimes  of  large  amounts — has  been  in- 
curred in  excess  of  the  loan  sanctioned  by  us 
in  respect  of  the  scheme.  In  some  instances 
this  has  resulted  from  under-estimating  the 
cost ;  in  others  it  has  transpired  that  the 
arrangements  which  we  approved  in  connec- 
tion with  the  proposal  for  the  original  loan 
have  been  extended  or  otherwise  varied  with- 
out our  consent It  is  important  that 

ratepayers  should  know  the  probable  cost  of 
a  proposed  scheme  before -it  is  decided  upon, 
and  we  trust  that  local  authorities  will  do 
their  best  to  see  that  the  estimates  which 
accompany  their  proposals  are  as  accurate 

and  as  complete  as  they  can  be  made 

No  material  alteration  should  be  made  without 
our  consent  in  the  plans  of  works  in  respect 
of  which  we  have  sanctioned  the  borrowing  of 
money.  In  some  cases  we  have  found  that 
departures  from  hospital  plans  provided  by  us 
have  involved  expenditure  which  we  could 
only  regard  as  needless  or  extravagant ;  we 
have  in  these  cases  declined  to  allow  the 
additional  expense  to  be  defrayed  out  of  loan 
monies." 

The  memorandum  of  May,  1902,  referred 
to  above  gives  specific  details  in  regard  to 
accommodation.  Thus,  in  the  ward-blocks 
each  bed  should  have  at  least  12  lin.  ft.  of 
wall  space,  144  sq.  ft.  of  floor  space,  and 
2,000  cu.  ft.  of  air  space ;  in  calculating  the 
latter,  any  height  of  wards  above  13  ft.  should 
not  be  taken  into  account.  All  inner  surfaces 
(of  walls,  floor,  &c.)  to  be  non-dust-harbouring. 
Ventilation  to  be  by  windows  on  opposite 
sides,  constructed  with  double-hung  sashes 


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and  hopper  fanlight  falling  inward  with  side     of  urban  and  rural  district  councils.     Parish 


cheeks.  Area  of  windows  proportioned  as 
1  sq.  ft.  to  every  70  cu.  ft.  of  ward  space. 
"Windows  to  face  south-east  and  north-west 
respectively.  Closets  and  slop-sinks  to  be 
placed  in  annexes  separated  from  the  wards 
by  cross-ventilated  lobbies.  Instructions  are 
also  given  as  to  other  buildings.  At  least 
40  ft.  must  be  left  between  any  building 
which  is  to  contain  infected  persons  or  things 
and  any  other  buildings.  The  drains  of  each 
block  must  be  trapped  from  the  common 
drain  and  ventilated  separately  by  an  inlet 
just  above  the  trap  and  by  ventilating  shafts 
at  their  highest  points.  Three  most  excellent 
plans,  setting  forth  all  these  and  numerous 
other  details,  accompany  the  memorandum. 
There  has  also  been  published,  under  date  of 
March,  1908,  an  appendix  to  this  memoran- 
dum, containing  a  fourth  plan  for  an  obser- 
vation block.  In  this  provision  is  made  for 
1,440  cu.  ft.  of  air-space  per  bed  in  lieu  of 
2,000  in  view  of  other  improvements  in 
construction.  W.  M.  F. 

Local  Government  Board  Require- 
ments :  Loans.  —  The  principal  bodies 
concerned  in  the  raising  of  loans  for 
sanitary  purposes  are,  (1)  county  councils, 
(2)  municipal  corporations,  (8)  urban  and 
rural  district  councils,  and  (4)  parish  councils. 
In  addition  to  these  principal  bodies,  lesser 
public  or  semi-public  bodies,  such  as  burial 
boards  and  port  sanitary  authorities,  are  also 
invested  with  borrowing  powers,  subject  to 
the  control  of  the  Local  Government  Board. 

The  raising  of  loans  and  their  repayment  is 
subject  in  part  to  statutory  provisions  and  in 
part  to  departmental  control.  Thus,  the 
Local  Government  Act,  1888,  by  which  county 
councils  were  created,  sets  out  the  purposes 
for  which  and  the  conditions  under  which  a 
county  council  may  borrow  money  ;  similarly, 
the  Municipal  Corporations  Act,  1882  (amended 
by  the  Local  Government  Act,  1888),  provides 
for  borrowing  by  town  councils,  whilst  the 
Public  Health  Act,  1875,  and  subsequent 
amending  Acts  provide  for  the  loan  necessities 


councils  derive  their  borrowing  powers  from 
the  Local  Government  Act,  1894 ;  and  the 
other  authorities  named,  from  the  Burial  Acts 
and  other  measures  particularly  affecting 
their  existence. 

Loans  may  be  raised  only  with  the  con- 
currence of  the  Local  Government  Board  into 
whose  hands  the  revisionary  powers  formerly 
exercised  by  the  Treasury  and  all  recently 
constituted  new  powers  have  been  placed. 
There  are  three  methods  in  which  loans  can 
be  raised,  i.e.,  (1)  by  the  issue  of  stock,  (2)  by 
mortgage,  and  (3)  by  borrowing  from  the 
Public  Works  Loan  Commissioners.  The 
issue  of  stock  by  local  bodies  is  provided  for 
mainly  by  the  Local  Government  Act,  1888, 
and  by  the  Public  Health  Acts  Amendment 
Act,  1890.  Under  both  these  Acts  the  Local 
Government  Board  are  authorised  to  issue 
regulations,  and  such  have  been  issued,  and 
are  in  operation,  under  dates  1891,  1897,  and 
1901,  and  appear  under  the  two  headings  of 
County  Stock  Regulations  and  Stock  Regula- 
tions respectively.  They  deal  with  the  issue 
of  stock  in  every  detail,  and  should  be 
consulted  whenever  particulars  are  required. 
As  regards  mortgages,  these  are  governed  by 
the  Commissioners  Clauses  Act,  1847,  and 
have  reference  to  the  security  which  the 
persons  termed  Commissioners  entrusted 
with  powers  to  carry  out  authorised  works 
may  give  for  the  loans  they  obtain.  The 
provisions  of  this  Act  have  been  incor- 
porated into  many  local  Acts,  and  also 
Acts  (like  the  Burial  Acts)  which  apply 
generally.  In  regard  to  loans  obtained  from 
the  Public  Works  Loan  Commissioners,  who 
are  a  body  brought  into  existence  by  the 
Public  Works  Loans  Act  of  1875,  it  may  be 
said  that  the  schedule  to  that  Act  specifies  the 
purposes  for  which  the  Commissioners  are 
empowered  to  lend  money,  and  to  this  list 
of  purposes  from  time  to  time  additions  are 
made  in  and  by  Acts  of  Parliament  passed  for 
new  objects  or  to  expand  existing  objects  of 
national  importance.  Thus,  the  Commis- 
sioners may  lend  money  to  local  authorities 


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MUNICIPAL   AND   SANITAEY   ENGINEERING. 


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whose  districts  do  not  exceed  in  rateable  value 
individually  £200,000,  for  such  purposes  as 
the  provision  of  allotments,  the  carrying  on  of 
education  (elementary  and  higher),  the 
purposes  of  the  Public  Health  Acts,  and  the 
provision  of  small  dwellings  for  the  working 
classes.  The  rules  under  which  the  Com- 
missioners lend  money  include  stipulations 
that  the  works  or  undertakings  shall  be 
entirely  new,  and  that  the  power  of  borrowing 
which  is  being  exercised  shall  not  have  been 
so  exercised  before.  Money  required  for  the 
purpose  of  repaying  an  old  loan  cannot  be 
obtained  from  the  Commissioners  ;  and  repay- 
ment is  generally  specified  under  an  annual 
system  extending  for  a  period  not  exceeding 
30  years.  (For  powers  to  borrow  for  specific 
purposes,  see  the  various  articles  under  separate 
headings).  W.  M.  F. 

Local  Government  Board  Require- 
ments :  Mortuaries. — In  dealing  with  appli- 
cations for  loans  by  local  authorities  for  the 
purpose  of  providing  mortuaries,  the  Local 
Government  Board  gives  some  assistance. 
They  have  provided  a  set  of  model  bye-laws 
under  section  141  of  the  Public  Health  Act, 
1875.  This  set  is  numbered  XV.  Mortuaries, 
dated  1896,  and  copies  (price  2cL)  can  be 
purchased  from  the  Government  printers.  To 
these  model  bye-laws  is  appended  a  memoran- 
dum dated  25th  July,  1882,  with  observations 
by  the  Local  Government  Board  as  to  the 
extent  to  which  local  authorities  ought  to 
avail  themselves  of  their  power  to  make 
proper  provision  for  dealing  with  dead  bodies 
which  come  under  their  care,  and  including 
suggestions  as  to  the  erection  of  mortuary 
buildings,  and  their  general  management. 
Sanitary  authorities  when  desirous  of  raising 
loans  for  such  purposes  must  obtain  the 
sanction  of  the  Local  Government  Board,  and 
that  sanction  may  be  taken  to  depend  upon 
the  adoption  of  the  suggestions  contained  in 
the  Memorandum  of  1882,  beyond  which  the 
most  important  consideration  is  that  of 
drainage,  and  in  regard  to  this  the  Board 
should  first  be  consulted.  Thirty  years  is  the 


usual  period  allowed  for  repayment  of  loans 
for  buildings  of  this  class  outside  the  Metro- 
polis. It  should  be  observed  that  outside  the 
Metropolis  local  authorities  have  no  statutory 
power  to  provide  buildings  in  which  to  hold 
coroners'  inquests,  but  are  in  a  position  to 
grant  the  use  of  portions  of  existing  buildings 
for  that  purpose. 

The  requirements  (or  "  suggestions  ")  of 
the  Board  as  to  site  and  structure  of  mor- 
tuaries are  given  in  the  Memorandum  XV. 
referred  to  above.  Buildings  should  be  con- 
cealed from  public  view ;  external  architecture 
to  "  serve  to  convey  the  impression  of  due 
respect  for  the  dead."  Every  chamber  in- 
tended for  the  reception  of  corpses  to  be  on 
the  ground  floor  ;  in  addition  a  waiting-room 
for  visitors  and  for  the  use  of  mourners 
assembling,  a  caretaker's  house,  and  a  shed 
or  outhouse  for  the  keeping  of  shells  and 
other  appliances.  The  mortuary  chamber  to 
have  a  ceiling,  or,  if  open  to  the  roof,  a  double 
roof  to  be  put  in  with  a  space  of  8  in.  between 
each  covering.  Louvres  or  air-gratings  for 
ventilation  under  the  eaves.  Windows  on  the 
north  side ;  if  necessary  elsewhere,  to  be  fitted 
with  external  louvre  blinds.  Cement  floors 
preferable.  Water  to  be  laid  on  with  a  tap  in 
the  chamber.  Shelves  and  tables  preferably 
to  be  made  of  slate  slabs,  and  to  be  placed  so 
that  their  upper  surfaces  may  be  from  2J  to 
3  ft.  above  the  floor.  Two  chambers  to  be 
provided — one  being  for  infectious  cases,  and 
this  should  be  placed  as  far  as  possible  away 
from  the  other.  The  entrance  to  each  chamber 
to  be  direct,  without  any  intervening  passage. 
These  principles  are  very  clearly  set  out  in  the 
plan  which  accompanies  the  memorandum. 

W.  M.  F. 

Local    Government    Board    Require- 
ments :  Sewage  and  Sewage  Disposal.— 

When  a  local  authority  is  proposing  to  inaugu- 
rate some  scheme  of  sewerage  or  of  sewage  dis- 
posal which  will  involve  the  borrowing  of  money 
under  the  provisions  of  sections  233  to  235  of  the 
Public  Health  Act,  1875,  the  sanction  of  the 
Local  Government  Board  must  be  obtained, 


263 


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and  in  order  to  obtain  that  sanction  the  scheme 
which  the  local  authority  is  proposing  to  adopt 
must  be  submitted  in  detail  for  the  approval  of 
the  Local  Government  Board.  If,  however, 
such  a  scheme  does  not  involve  the  borrowing 
of  money,  it  will  not  be  necessary  to  seek  any 
such  approval,  though,  of  course,  the  general 
powers  of  intervention  by  the  Board  remain. 
The  Local  Government  Board  do  not  favour 
any  particular  scheme,  but  leave  it  to  the 
local  authority  to  consult  their  own  engineers 
and  formulate  such  a  scheme  as  appears  to 
them  to  be  suited  to  the  requirements  of  their 
own  particular  district.  Such  schemes  natur- 
ally vary  considerably,  but  as  there  is  no  fixed 
scheme,  and  as  there  are  no  specific  plans 
recommended  for  adoption  by  the  Local 
Government  Board,  it  is  only  necessary  that 
the  scheme  propounded  and  submitted  should 
conform  to  certain  general  requirements.  The 
scheme,  whatever  it  may  be,  must  be  definitely 
adopted  and  approved  by  the  local  authority 
before  it  is  submitted  to  the  Local  Government 
Board.  The  general  requirements  of  the 
Board  fall  practically  under  three  headings  : 

1.  Requirements  as  to  the  period  fixed  for 
repayment  of  the  proposed  loan. 

2.  Certain     undefined     suggestions    made 
from  time  to  time  in  the  annual  reports  and 
the   published   correspondence  of   the   Local 
Government  Board. 

3.  Certain  definite  requirements  set  out  in 
the  form  of  estimate  (K.  No.  29). 

As  TO  PERIODS   OF  REPAYMENT.  —  The  fol- 
lowing is  taken  from  the  Report  of  the  Select 
Committee  on  Repayment  of  Loans  (1902)  as 
being  a  list  of  the  periods  usually  allowed  by  the 
Local  Government  Board  for  the  repayment  of 
loans  sanctioned  for  sewage  purposes  : — 
Land  Purchase       .         .         .60  years. 
Sewers  and  surface  water  drains 
and  such  ordinary  works  as 
tanks,  filters,  Ac.         .         .     30  years. 
Sewage  Lifts  .         .         .30  years. 

Ejectors         .         .         .         .15  years. 
Polarite  .  .10  years. 

Sludge  Presses       .         .         ,10  years. 
Farming  Stock        .         .         .     5  to  10  years. 


For  general  observations  on  this  topic  see 
Local  Government  Board  Report,  1906-7. 

INDEFINITE  SUGGESTIONS  AMOUNTING  MORE 
OR  LESS  TO  REQUIREMENTS. — These  are  both 
varied  and  numerous,  and  they  include  such 
general  principles  as  concern  estimated  costs, 
employment  of  engineers,  the  adoption  of 
competitive  schemes,  and  the  management  or 
supervision  of  sewage-disposal  works.  In 
regard  to  the  last-named,  the  Board  favour  the 
retention  by  local  authorities  of  this  manage- 
ment in  their  own  hands  (but  see  Local  Govern- 
ment Board  Annual  Report  for  1902-3,  where 
special  reference  is  made  to  the  need  for 
skilled  supervision).  In  dealing  with  applica- 
tions to  sanction  loans  for  sewerage  purposes, 
the  Local  Government  Board  require  not  only 
full  and  complete  details  and  plans,  but  also  a 
variety  of  miscellaneous  information  as  to 
rateable  value  of  the  district  where  the  loan  is 
to  be  repaid  from,  and  satisfactory  proof  of  all 
necessary  consents  having  been  obtained, 
together  with  details  of  existing  works  pro- 
posed to  be  superseded,  in  respect  of  which 
there  may  be  a  portion  of  an  earlier  loan  still 
outstanding. 

DEFINITE  REQUIREMENTS. — These  are  mostly 
set  out  in  the  form  of  estimate  (K.  No.  29),  but 
not  entirely  so.  They  may  be  expressed, 
however,  in  the  following  classification1  :— 

I.  Sewers. — (a)  In  the  case  of  brick  sewers, 
radiated  bricks  to  be  used  when  obtainable. 

(/>)  Side  junctions  for  house  drains  to  be 
inserted  in  brick  sewers  at  the  time  of  con- 
struction. Junction  pipes  to  be  provided  on 
all  pipe  sewers. 

(c)  Main  sewers  as  far  as  practicable  to  be 
laid  at  such  depth  and  with  such  gradients  as 
to  afford  means  for  draining  the  cellars  and 
basements  of  houses. 

(d)  Sewers  laid  under  roadways  to  have  at 
least  4  ft.  of  cover   between  the   top  of  the 
pipes  and  the  surface  of  the  horse-road ;  but 
when  this  is  impracticable  the   pipes  to  have 

1  Extracted  from  Wood  and  Johnson's  "  Encyclo- 
paedia of  Local  Government  Board  Requirements," 
Vol.  II.,  Part  57,  where  the  details  are  very  fully  set 
out. 


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a  6-in.  coating  of  concrete.  This  latter 
requirement  applies  also  where  the  pipes  are 
laid  in  the  roadways  at  a  depth  exceeding 
15  ft.  Where  they  are  laid  under  fields  there 
is  to  be  at  least  3  ft.  of  cover. 

(e)  Sewers  to  be  laid  in  straight  lines  with 
manholes  at  all  changes  of  direction  or 
gradient,  and  no  two  manholes  to  be  more 
than  100  yards  apart. 

(/)  All  manholes  and  underground  cham- 
bers in  roadways  to  be  of  sufficient  strength 
to  carry  the  heaviest  traction  engine  or  other 
traffic  likely  to  pass  over  them. 

(<-/)  All  joints  to  be  of  cement  and  not  clay. 

(/<)  Efficient  ventilation  to  be  provided. 

(i)  Adequate  measures  to  be  adopted  for 
preventing  the  infiltration  of  sub-soil  and 
surface  water  into  the  sewers. 

(j)  A  storm  overflow  to  be  constructed  in 
such  a  way  as  not  to  come  into  operation 
until  the  ordinary  dry  weather  flow  of  sewage 
has  been  diluted  with  five  times  its  volume  of 
storm  water. 

II.  Machinery.  —  All  pumping  machinery 
to  be  provided  in  duplicate. 

III.  Setvage  Disposal. — The   requirements 
of  the  Local  Government  Board  here  depend 
upon  whether  the  scheme  submitted  to  them 
is  one  which  involves  the  discharge  of  sewage 
matter   into   non-tidal  rivers.     If  it   does   it 
must  include  proper  provision  for  the  purifi- 
cation of  the  sewage  upon  an  adequate  area  of 
land,  in  addition  to  any  preliminary  treatment 
it  may  undergo,  and  this  will  be  insisted  upon 
unless  it  can  be  shown  that  land  suitable  for 
the  purpose  cannot  be  obtained.    With  regard 
to  the  area  required,  this  will  vary  in  different 
cases,    and   will    depend  not   only    upon  the 
quality  of  the  sewage,  but  also  upon  the  nature 
of  the  land  available,  and  further,   upon  the 
details  of  the  preliminary  process  suggested. 
Where,  however,  it  is  only  proposed  to  deal 
with  domestic  sewage  and  land  is  available, 
the   Local   Government   Board  require  as  a 
minimum    the  following  proportions  of  area 
per  population  :— 

Broad  irrigation  (without  any  previous 
treatment)  one  acre  of  land  to  every  150 

265 


persons  of  the  population  of  the  area  to  be 
drained. 

Irrigation  after  bacterial  process,  one  acre 
to  every  1,000  persons,  or  one  acre  to  every 
30,000  gallons  of  drainage. 

Other  methods,  one  acre  to  every  1,000  or 
2,000  persons  according  to  the  system  pro- 
posed to  be  adopted. 

Where  it  is  intended  to  construct  bacteria 
beds  for  sewage  treatment,  the  following 
requirements  are  also  specified  : — 

(a)  The  beds  must  be  large  enough  to  deal 
with  twice  or  three  times  the  dry  weather  flow 
of   sewage  according  as  the  district  may  or 
may    not    have    a    separate     surface    water 
drainage  system. 

(b)  Where  the  beds  are  to  be  worked  on  the 
contact   principle    and  the  sewage  is    to    be 
finally  treated  on  land,  one,  i.e.,  single  con- 
tact, will  suffice.     The  working  capacity  of  the 
beds  will  be  taken  at  one-third  of  the  capacity 
of  the  tanks  after  the  filtering  material  has 
been  put  in,  and  there  must  not  be  more  than 
three  fillings  in  24  hours. 

(c)  Where  the  filters  are  to  be  worked  on  a 
percolating  principle  and   land  treatment  is 
provided,  the  maximum  rate  of  filtration  must 
not  exceed  56  gallons  per  square  yard  per  foot 
in  depth  of  filtering  material  per  day. 

(d)  Where  land  treatment  is  impossible  the 
cubic  contents  of  the  filtering  matter  in  either 
case  must  be  double  what  is  indicated  under 
(b)  and  (c). 

(e)  Provision  must  be  made,  in  addition  to 
what  has  already  been  provided  for  the  dry 
weather  flow,  for  dealing  with  up  to  at  least 
six  times  its  volume  by  providing  extra  land 
or  by  passing  it  through  storm  water  filters 
capable    of    admitting    a    continual   rate   of 
filtration  not  exceeding  500  gallons  per  square 
yard  per  day. 

(/)  Where  septic  tanks  are  to  be  provided, 
their  capacity  should  not  be  less  than  tbe 
ordinary  daily  dry  weather  flow  of  sewage  to 
the  outfall. 

Special  requirements  have  to  be  considered 
in  regard  to  applications  by  local  authorities 
to  the  Local  Government  Board  for  sanction 


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ENCYCLOPAEDIA   OF 


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to  loans  under  section  32  of  the  Public  Health 
Act,  1875,  for  the  construction  of  works  out- 
side the  district  of  the  local  authority.  In  a 
case  of  this  kind  it  is  usual  for  the  Local 
Government  Board  not  to  make  an  inquiry 
until  the  time  has  expired  during  which 
objections  may  be  lodged  in  order  to  avoid 
the  unnecessary  expense  of  having  a  further 
inquiry  later  on.  In  urgent  cases,  however, 
and  if  there  is  not  much  likelihood  "of  objec- 
tions being  made,  the  Local  Government 
Board  will,  on  application,  arrange  for  an 
inquiry  to  be  held  without  waiting  for  the 
usual  time  to  expire.  This  inquiry  having 
been  held,  the  period  of  objection  must  be 
allowed  to  expire  and  the  matter  can  then  be 
dealt  with  immediately.  A  copy  of  the  statu- 
tory declaration  required,  also  copies  of  the 
newspapers  containing  the  necessary  adver- 
tisements, should  be  forwarded.  If  no 
objection  has  been  made,  the  fact  should  be 
stated  ;  but  if  any  objection  has  been  made, 
a  resolution  must  be  passed  and  a  copy  of  it 
be  forwarded  requesting  the  Local  Govern- 
ment Board  to  appoint  an  inspector  to  make 
further  inquiry  and  report.  W.  M.  F. 

Local  Government  Board  Require- 
ments: Water  Supply.  — Under  the  pro- 
visions of  the  Public  Health  Act,  1875,  certain 
local  authorities  are  empowered  to  construct 
and  maintain  waterworks  and  take  over  and 
lease  or  hire  waterworks  and  to  contract  with 
any  person  or  persons  for  water  supplies;  but  if 
they  wish  to  purchase  any  waterworks  or  any 
right  to  take  over  or  convey  water,  either 
within  or  without  their  district,  they  must 
obtain  the  sanction  of  the  Local  Government 
Board.  In  fact,  it  comes  to  this,  that  when  a 
local  authority  wishes  to  raise  money  for  the 
purpose  of  providing  a  water  supply,  the 
Local  Government  Board  will  bave  to  be 
consulted,  and  then  there  are  certain  require- 
ments which  will  have  to  be  complied  with. 
The  Local  Government  Board  do  not  specify 
what  these  requirements  are,  although  they 
supply  an  official  form  of  estimate  (K.  No.  20), 
in  which  the  local  authority  should  set  forth 


full  details  of  the  estimated  cost  of  the  scheme. 
It  is  understood  that  although  they  do  not 
publish  any  special  information,  nor  do  they 
issue  any  plans  for  the  guidance  of  the  local 
authorities,  or  do  anything  else  to  furnish  in 
a  succinct  form  the  particular  requirements 
to  be  met,  they  do  have  regard  to  various 
matters  which  they  deal  with  on  general  lines. 
Their  requirements  maybe  brought  practically 
under  two  headings  : — 

(1.)  As  to  the  financial  aspect  of  the  pro- 
posed scheme  ;  and 

(2.)  As  to  the  practicability  or  sufficiency 
of  the  proposed  supply. 

(1.)  Of  course  the  Board  go  very  fully  into 
the  financial  aspects  of  the  matter,  and  apart 
from  the  provisions  of  the  Public  Health  Act, 
1875,  and  the  Public  Health  (Water)  Act,  1878, 
with  regard  to  the  incidence  of  expenses,  they 
consider  carefully  the  whole  subject  of  cost  in 
the  interests  of  the  ratepayers  of  the  area  so 
affected.     Then  as  to  the  repayment  of  pro- 
posed loans,    the    following  are    the   periods 
allowed  for  such  repayments  in  the  case  of  loans 
sanctioned  for  the  water  supply  purposed : — 
Purchase  of  land  (freehold)   .         .     60  years. 
Mains  and  pipes    .         .         .         .     30      ,, 
Beservoirs     .         .         .         .         .     30      ,, 
Water  towers          .         .         .  30      ,, 

Purchase  of  existing  undertakings.  30  ,, 
Machinery  .  .  .  .  .  15  ,, 
Waste  water  meters  .  .  .  10  ,, 
Boring  experiments  .  .  5  ,, 

It  should  be  pointed  out  that  a  local 
authority  may  apply  for  loans  in  respect  of 
three  different  schemes,  that  is  to  say,  for  the 
carrying  out  of  purely  experimental  works,  or 
for  the  taking  over  of  existing  waterworks,  or 
for  the  construction  of  new  works  entirely. 

(2.)  As  TO  THE  PROJECTED  SUPPLY. — The 
Local  Government  Board  require  first  of  all 
that  any  scheme  shall  provide  if  possible  for 
not  less  than  the  undermentioned  quantities 
per  day  per  head  of  the  population  : — 

10  to  15  gallons  in  agricultural  villages  ; 

16  to  20  gallons  in  non-manufacturing 
towns  ; 

20  to  30  gallons  in  manufacturing  towns. 
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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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As  regards  the  laying  of  mains,  cast-iron  pipes 
should  be  used,  not  galvanized,  iron,  stone  or 
earthenware,  and  the  mains  should  be  laid 
at  a  depth  of  not  less  than  3  ft.  from  the 
surface  reckoned  from  the  top  of  the  pipe,  and 
should  be  at  least  3  in.  in  diameter  except 
there  be  special  reasons.  Hydrants  to  be 
provided  at  all  dead  ends.  Screw-down 
hydrants  are  to  be  used  in  preference  to  ball 
hydrants.  The  pumping  machinery  to  be 
provided  in  duplicate ;  and  all  sources  of  supply, 
reservoirs,  and  the  like  to  be  protected  by 
uncliuibable  fencing.  AY.  M.  F. 

"  Loco  "  Apparatus. — A  series  of  drain- 
age appliances — bends,  traps,  &c. — designed  by 
Mr.  F.  C.  Lynde,  C.E.  The  principle  under- 
lying these  apparatus  is 
the  law  of  deflection. 
With  this  purpose  in  view 
the  bends,  &c.,  are  made 
with  flat  striking  sur- 
faces in  the  interior,  so 
arranged  that  water,  &c., 
falling  upon  these  verti- 
cally will  be  deflected  down  the  horizontal 
drain,  without,  it  is  claimed,  loss  of  flushing 
power.  The  principle  involved  is  made  clear 
in  the  accompanying  illustration  which  is  a 
longitudinal  section  through  a  "  Loco  "  bend. 

London  Main  Drainage.  —  The  first 
sewers  in  London  consisted  of  the  natural 
watercourses,  ditches,  &c.,  which  were  covered 
in  and  converted  into  sewers  for  the  carriage 
of  surface  waters  only.  Water-closets  were 
introduced  about  1810 ;  but  they  had  to 
be  made  to  discharge  into  cesspits,  as  it 
was,  up  to  the  year  1815,  a  penal  offence  to 
discharge  polluting  matters  into  the  sewers. 
Prior  to  1847  the  sewers  of  London  were 
under  the  management  of  eight  different 
Commissions ;  but  in  that  year  they  were 
superseded  by  one  general  Commission  termed 
"  The  Metropolitan  Commission  of  Sewers," 
the  members  of  which  directed  their  atten- 
tion mainly  to  a  consideration  of  the  kinds 
of  sewers  to  be  adopted  and  to  the  abolition 


"  Loco  "  Apparatus. 


of  cess-pits.  In  1847  an  Act  was  passed 
making  it  compulsory  to  discharge  house  drains 
into  the  sewers,  the  result  of  which  was 
that  within  about  6  years  30,000  cesspools 
were  abolished,  and  the  whole  of  the  sewage 
of  London  was  turned  into  the  Thames.  The 
river,  naturally,  soon  became  very  foul,  and 
between  the  years  1849  and  1854  no  less  than 
five  different  Commissions  were  formed  to 
deal  with  the  evils  arising  out  of  this  new 
state  of  affairs.  In  1856  the  Metropolitan 
Board  of  Works  came  into  being  under  the 
powers  of  the  Metropolis  Management  Act  of 
1855. 

One  of  the  first  acts  of  the  new  Board  was 
to  attempt  the  complete  interception  of  the 
sewage  so  as  to  discharge  it  into  the  river 
below  London  and  beyond  the  boundaries  of 
the  metropolis.  This  they  did  by  constructing 
intercepting  sewers  parallel  to  the  river,  into 
which  the  existing  main  sewers  were  con- 
nected. These  conveyed  the  sewage  on  the 
north  side  to  Barking,  and  on  the  south  side 
to  Crossness.  Three  intercepting  sewers  were 
constructed  on  the  north  side,  the  low-level, 
middle-level,  and  the  high-level.  The  high 
and  middle-level  sewers  conveyed  the  sewage 
by  gravitation  to  Old  Ford,  from  where  they 
ran  together  as  far  as  Abbey  Mills,  at  which 
point  the  sewage  from  the  low-level  sewer  is 
pumped  into  them,  after  having  been  already 
raised  once  at  the  Western  Pumping  Station 
at  Pimlico.  From  Abbey  Mills  the  sewage  is 
conveyed  to  Barking  by  gravitation  in  what  is 
known  as  the  northern  outfall. 

On  the  south  side  of  the  river  there  are  also 
three  intercepting  sewers — the  low-level,  high- 
level,  and  the  En'ra  branch  sewer.  The  high- 
level  and  the  Effra  branch  sewers  convey  the 
sewage  by  gravitation  to  Deptford,  at  which 
point  the  sewage  from  the  low-level  sewer  is 
pumped  into  them.  From  here  the  sewage  is 
conveyed  by  gravitation  in  the  southern  out- 
fall sewer  to  Crossness,  where  the  whole  of 
the  sewage  has  to  be  pumped.  Storm  over- 
flow weirs  were  constructed  at  the  junctions 
of  the  old  main  sewers  with  the  intercepting 
sewers,  so  that  if  heavy  rains  should  cause  the 


267 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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flow  in  the  latter  to  become  excessive  it  could 
overflow  into  the  old  sewers,  and  thus  go  direct 
into  the  Thames. 

The  construction  of  the  intercepting  sewers 
effected  a  great  improvement,  not  only  by 
removing  the  sewage  to  a  distance  before  it 
was  discharged  into  the  river,  but  also  by 
reducing  the  amount  of  flooding  in  low-lying 
areas  that  had  formerly  taken  place.  Under 
the  old  system  the  main  sewers  were  only  able 
to  discharge  their  contents  at  or  about  the 
level  of  low  water,  the  rise  of  the  tide  closing 
the  outlets,  with  the  result  that  any  sewage 
flowing  down  during  the  period  the  outlets 
wrere  closed  was  pounded  back  in  the  main 
sewers.  In  times  of  heavy  and  long-con- 
tinued rain,  and  more  particularly  when  such 
occurred  at  the  time  of  high  water  in  the  river, 
the  closed  sewers  were  unable  to  store  the 
increased  volume  of  sewage,  which  then  rose 
through  the  house  drains  and  flooded  the  base- 
ments of  the  houses.  This  being  the  case,  it 
will  be  seen  that  the  provision  made  for  dis- 
charging excessive  rainfall  by  means  of  the 
old  sewers  could  not  be  satisfactory  at  all 
times.  Under  these  circumstances  the  Metro- 
politan Board  of  Works,  in  1879,  decided  to 
carry  out  the  following  flood  relief  works  : — 

(1.)  Storm  relief  line  for  the  Ranelagh  and 
King's  Scholars'  Pond  sewers. 

(2.)  Storm  relief  line  for  the  Ratcliffe 
Highway  and  Limekiln  Dock  sewers. 

(3.)  Relief  line  for  the  high-level  sewers 
at  Hackney. 

(4.)  Intercepting  sewer  from  Putney  to 
Clapham. 

(5.)  Storm  relief  to  high-level  at  High 
Street,  Clapham,  to  discharge  into  Effra 
Creek,  Yauxhall. 

(6.)  Deptford,  storm  overflow. 

(7.)  Sewer  from  Lee  Bridge  to  Deptford. 

(8.)  Sewer  to  relieve  low-lying  ground  at 
Walworth. 

(9.)  Storm  sewer  to  relieve  Holloway  and 
Kentish  Town. 

The  total  estimated  cost  of  these  works 
amounted  to  £708,000,  and  all  the  sewers 
wore  constructed  with  the  exception  of  the 


sewer  at  Walworth ;  but  a  relief  sewer  was 
made  from  Rotherhithe  New  Road  to  South- 
wark,  knowrn  as  the  Grange  Road  sewer. 

In  1897  the  Main  Drainage  Committee  of 
the  London  County  Council,  who  took  over 
the  control  of  the  sewers  of  the  metropolis  in 
1889,  instructed  their  engineer,  Sir  Alexander 
Binnie,  to  consider  the  whole  main  drainage 
system,  with  the  result  that  he  reported 
that  the  following  works  were  the  most 
urgent : — 

NORTH  SIDE  or  RIVER. — Two  sewers,  Old 
Ford  to  Barking ;  new  middle-level  sewer, 
Paddington  to  Old  Ford ;  new  low-level  sewer, 
Hammersmith  to  Bow  ;  extension  of  middle- 
level  sewer  to  Scrubb's  Lane,  Willesden ; 
pumping  machinery  at  Abbey  Mills. 

SOUTH  SIDE  OF  RIVER. — Low-level  sewer, 
Deptford  to  Crossness ;  high-level  sewer, 
Catford  to  Crossness;  low-level  sewer,  Batter- 
sea  to  Deptford. 

The  total  estimated  cost  of  these  works 
amounted  to  £2,947,000.  The  greater  part 
of  them  have  been  constructed,  some  are  in 
progress,  and  others  nearly  ready  for  contract. 
In  addition  to  these  works,  six  pumping 
stations  were  constructed  to  relieve  the  low- 
lying  intercepting  sewers — three  on  the  north 
side  of  the  river  at  Lot's  Road,  King's 
Scholars'  Pond,  and  Isle  of  Dogs  ;  and  three 
on  the  south  side — at  Falcon  Brook,  Heath- 
wall,  and  Shad  Thames. 

The  new  sewers  already  in  operation  have 
greatly  diminished  the  number  of  discharges 
of  rainfall  into  the  Thames  within  the  County 
of  London,  but  in  spite  of  their  construction 
a  considerable  amount  of  flooding  occurred  in 
many  parts  of  London  in  1903,  when  a  total, 
of  35  in.  of  rain  fell.  The  Main  Drainage 
Committee  of  the  London  County  Council 
therefore  decided  in  1904  to  carry  out  the 
following  additional  flood  relief  works  at  a 
total  estimated  cost  of  £737,000. 

SUGGESTED  FLOOD  RELIEF  WORKS. — NORTH 
SIDE  :  (1)  Storm  relief  sewyer,  Holloway  to  the 
Thames  ;  (2)  storm  relief  sewer  from  middle- 
level  sewer  to  Counters  Creek  sewer  (North 
Kensington  storm  relief  sewer) ;  (3)  extension 


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of  Hackney  Wick  relief  sewer,  northwards ; 
(4)  Stroud  Green  storm  relief  sewer. 

SOUTH  SIDE  :  (5)  Storm  water-pumping 
station  at  Wandsworth  (the  Falcon  Brook 
station  already  mentioned) ;  (6)  new  sewers 
in  connection  with  the  above  pumping  station ; 

(7)  storm  water  pumping  station  to  deal  with 
storm  water  in  Southwark  and  Bermondsey 
(the  Shad  Thames  station  already  mentioned) ; 

(8)  Southwark  and  Bermondsey  storm  relief 
sewer. 

Some  of  these  works  have  been  completed 
and  others  are  in  course  of  construction.  The 
bulk  of  the  rainwater  carried  by  the  sewers 
is  now  taken  to  the  outfalls  and  treated  before 
it  is  discharged,  and  there  will  be  a  still 
further  improvement  in  this  respect  as 
soon  as  the  completed  scheme  comes  into 
operation. 

The  total  discharging  capacity  of  the  out- 
falls and  storm  water  pumping  stations  on 
both  sides  of  the  river,  not  including  the  dis- 
charging capacity  of  those  storm  relief  sewers 
which  act  by  gravitation,  is  1,464,000,000 
gallons  per  24  hours. 

The  average  dry  weather  flow  per  24  hours 
amounted  in  1908  to  283,000,000  gallons,  so 
that  provision  has  been  made  to  deal  with 
1,181,000,000  gallons  of  storm  water  per  24 
hours,  apart  from  the  capacity  of  the  relief 
sewers  discharging  direct  in  to  the  river.  This 
is  equivalent  to  a  rainfall  of  about  0*70  in. 
over  the  whole  area  of  the  metropolis  in  24 
hours. 

Originally  the  whole  of  the  sewage  was 
stored  at  the  Barking  and  Crossness  outfalls 
during  the  flood  tide  and  discharged  on  the 
ebb  tide  in  its  crude  state.  In  1887,  however, 
the  Metropolitan  Board  of  Works  commenced 
the  construction  of  precipitation  works  at 
Barking,  and  in  1888  at  Crossness.  The 
sewage  when  it  arrives  at  the  works  is  sub- 
jected to  chemical  treatment :  the  addition  of 
1  grain  of  proto- sulphate  of  iron  (ferrous  sul- 
phate) and  4  grains  of  lime  to  every  gallon 
of  crude  sewage.  The  precipitation  takes 
place  in  long  channels.  The  sewage  flows  in 
at  one  end  of  each  channel,  and  after  the 


heavier  matters  are  precipitated  the  clarified 
sewage  goes  over  a  weir  at  the  other  end  of 
the  channel  into  the  river.  After  a  certain 
period  each  channel  is  shut  from  the  inlet  of 
sewage,  and  the  heavier  matter  left  in  the 
channel  is  dealt  with  in  the  following  manner. 
The  water  is  run  off  from  the  channels  by 
means  of  floating  arms,  and  the  wet  sludge 
is  pushed  through  screens  by  hand  into  a 
sump.  From  this  it  is  pumped  into  sludge- 
settling  channels  where  it  remains  for  about 
24  hours.  The  supernatant  water  on  the  top 
of  the  settled  sludge  is  drawn  off  by  means  of 
telescopic  weirs,  and  is  treated  with  20  grains 
of  lime  and  10  grains  of  iron  per  gallon,  after- 
wards being  pumped  up  to  the  outfall  sewer 
to  mix  with  the  rest  of  the  sewage.  The 
clarified  liquid  is  discharged  continuously  into 
the  river  at  all  states  of  the  tide.  The  settled 
sludge  gravitates  to  a  sludge  store,  from  which 
it  is  pumped  into  sludge  ships  which  take  it 
out  to  sea  and  deposit  it  at  Black  Deep  in  the 
estuary  of  the  Thames,  over  a  distance  of 
from  8  to  10  miles.  Six  sludge  vessels  are 
constantly  employed  for  this  work,  each 
holding  about  1,000  tons,  and  about  8,200 
tons  of  sludge  are  disposed  of  pet- -diem. 

The  area  draining  into  the  Coimcirs  sewers 
in  1901  was  about  140  sq.  miles,  and  the 
population  was  5,136,192  persons.  The  dis- 
charging power  of  the  northern  outfall  sewer 
at  Barking  under  present  conditions  is  about 
500,000,000  gallons,  and  of  the  southern 
outfalls  at  Crossness,  513,000,000  gallons  per 
24  hours.  The  permanent  staff  employed  in 
cleansing  the  sewers  at  the  pumping  stations 
and  outfall,  works,  and  on  the  sludge  boats 
varies  from  900  to  1,000  men. 

The  total  length  of  the  main,  intercepting, 
and  outfall  sewers,  when  those  in  course  of 
construction  and  those  about  to  be  constructed 
have  been  completed,  will  be  nearly  352  miles. 
The  net  capital  expenditure  on  the  sewers  and 
works  of  sewerage  up  to  March,  1909,  has 
been  £11,110,389,  and  it  is  estimated  that  an 
additional  expenditure  of  about  £1,500,000 
will  be  required  to  complete  the  schemes 
already  sanctioned  by  the  Council. 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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Much  of  the  information  given  above  has 
been  obtained  from  a  report  which  was  pre- 
pared for  the  Council  by  their  engineer, 
Mr.  Maurice  Fitzmaurice,  C.M.G.,  M.A., 
M.Inst.C.E.,  from  which  the  accompanying 
plan  has  also  been  reproduced.  H.  C.  H.  S. 

London  Water  Supply. —  London  is 
supplied  with  water  from  several  sources  and 
by  many  works,  formerly  under  the  control 
of  separate  waterworks  companies,  but  now 
under  the  control  of  the  Metropolitan  Water 
Board.  The  sources  of  supply  are  four  in 
number  (1)  the  river  Thames,  (2)  the  river 
Lea,  (3)  natural  springs,  and  (4)  wells  sunk 
in  the  chalk  or  other  strata  in  the  Lea  Valley, 
on  the  North  of  the  Thames,  in  Kent,  and  at 
certain  other  places  South  of  the  Thames. 

Speaking  roughly  about  56  %  of  the  total 
supply  of  London  is  drawn  direct  from  the 
Thames,  20%  from  the  Lea,  14%  from 
springs  and  wells  in  the  Lea  Valley,  9% 
from  wells  in  Kent,  and  1  %  from  wells  in 
the  southern  district. 

The  total  population  served  by  the  London 
mains  is  about  7,000,000  persons,  the  exact 
total  being  6,943,412  as  stated  in  the  annual 
report  of  the  Metropolitan  Water  Board  for 
the  year  ending  March  31,  1908. 

The  bulk  of  the  London  water  supply  being 
drawn  from  the  Thames  and  Lea  has  to 
be  purified  before  it  reaches  the  consumer. 
The  methods  of  purification  adopted  are 
(a)  natural  purification  by  storage  and  sub- 
sidence in  open  reservoirs  of  large  capacity, 
and  (6)  filtration  after  storage.  The  storage 
reservoirs  are  generally  formed  by  enclosing 
large  areas  with  earthwork  embankments 
made  watertight  by  means  of  thick  core 
walls  of  puddled  clay.  The  filters  are  con- 
structed of  sand  laid  upon  gravel  and  large 
stones  above  a  false  bottom  so  as  to  ensure 
ample  drainage.  The  water  after  filtration 
is  pumped  to  service  reservoirs  which  are 
generally  roofed  in  order  to  protect  the  water 
from  dust  and  foreign  matters,  and  also  from 
the  action  of  the  sunlight  which,  though 
beneficial  to  purification  in  the  open  storage 


reservoirs,  would  be  apt  to  produce  a  growth 
of  green  weed  in  the  hard  London  water 
which  would  render  it  unsuitable  for  drinking 
purposes.  The  water  which  is  derived  from 
purer  sources,  such  as  wells,  is  pumped  direct 
to  the  service  reservoirs,  and  in  some  cases 
the  well  water  and  the  filtered  river  waters 
are  mixed. 

The  service  reservoirs  are  situated  as  far 
as  possible  at  such  levels  as  will  supply  a 
district  or  area  by  gravitation.  Where  it  is 
impossible  or  inexpedient  to  make  the  high- 
level  service  reservoir  large  enough  to  hold 
many  hours'  supply  for  its  district  a  larger 
service  reservoir  is  made  at  a  lower  level,  and 
from  it  the  high-level  reservoir  is  supplied  by 
pumping.  The  high-level  reservoir  in  this 
case  is  sometimes  merely  a  device  for  keeping 
the  pressure  in  the  service  mains  constant, 
the  real  immediate  source  of  supply  being  the 
reservoir  at  the  lower  level.  The  water  thus 
obtained  and  stored  is  distributed  in  cast- 
iron  mains  of  sizes  which  vary  from  54  in. 
diameter  as  a  maximum  to  2  in.  diameter 
as  a  minimum.  These  mains  are  governed 
by  means  of  sluice  valves  in  such  a  manner 
that  any  whole  district,  section,  main  or 
branch  pipe  can  be  shut  off  in  case  of  need. 
Hydrants  for  fire  and  other  purposes  are 
connected  to  the  mains  in  the  streets  and  else- 
where, and  separate  connecting  pipes — one  for 
each  house — convey  the  water  to  the  houses ; 
each  service  pipe  is  governed  by  its  own  valve 
or  stop-cock  outside  the  property  to  which  it 
conveys  water.  No  other  waterworks  system 
in  the  world  is  comparable  with  that  of 
London.  The  vast  character  of  the  works 
under  the  control  of  the  Metropolitan  Water 
Board  may  be  gathered  from  the  following 
figures  which  are  taken  from  the  annual 
report  of  the  Metropolitan  Water  Board  for 
the  year  ending  March  31, 1908.  In  that  year 
over  80,000,000,000  gallons  of  water  were 
consumed  in  London,  the  average  daily  supply 
being  219,000,000  gallons.  The  average  daily 
supply  per  head  was  32*84  gallons.  There 
were  then  62  reservoirs  for  storage  and 
subsidence  holding  8,913,600,000  gallons,  or 


271 


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about  40  days'  supply,  and  in  addition  to 
this  another  6,000,000,000  gallons  storage  was 
authorised,  and  in  immediate  contemplation, 
the  works  for  which  have  since  been  put  in 
hand,  the  reservoirs  at  Walton  having  been 
opened,  and  those  at  Chingford  to  hold 
5,000,000,000  gallons  having  been  commenced. 
Besides  the  storage  reservoirs,  the  report 
already  quoted  describes  78  service  reservoirs 
holding  in  all  243,000,142,000  gallons.  The 
niters  were  161  in  number  and  covered  an 
area  of  16T91  acres.  There  were  37  pumping 
stations  containing  257  engines  having  a  total 
horse-power  of  34,645,  while  some  of  the 
pumps  were  lifting  water  to  a  height  of  600  ft. 
There  were  6,116  miles  of  water  main  and 
66,809  hydrants.  The  use  to  which  these 
hydrants  are  put  may  be  understood  from  the 
fact  that  during  the  year  in  question  there 
were  no  fewer  than  2,800  fires  in  the  area  of 
the  Metropolitan  Water  Board. 

The  Board  have  divided  their  area  into  five 
engineering  districts : — 

1.  The  Eastern  district  deriving  its  supply 
from  the   rivers  Thames  and  Lea  and  from 
eleven  wells  in  the  Lea  Valley. 

2.  The  Kent  district,  which  is  independent 
of  the  Thames  and  Lea,  being  supplied  solely 
from  deep  wells. 

3.  The    New   River    district    deriving    its 
supply   from   the    river   Lea,    the    Chadwell 
spring,    and    from     18    wells     in    the    Lea 
Valley,  most  of  which   feed   the  New  River 
Channel,  and  also  from  the  Thames  by  inter- 
communication;    a    small   supply    for    non- 
domestic  purposes  is  also  obtained  from  the 
Hampstead  and  Highgate  Ponds. 

4.  The  Southern  district,  which  derives  its 
main  supply  from  the  Thames  with  a  sup- 
plementary  source   from   wells   at    Selhurst, 
Streatham,  Honor  Oak,  and  Merton  Abbey. 

5.  The  Western  district,  which  is  supplied 
only  from  the  Thames. 

The  intakes  on  the  river  Thames  are 
situated  at  Walton  and  Molesey.  Those 
upon  the  river  Lea  are  at  Enfield  Lock,  and 
the  intake  of  the  New  River  district  is  situated 
between  Hertford  and  Ware  Locks  on  the 


river  Lea.  The  present  policy  of  the  Water 
Board  is  to  increase  the  storage  capacity  by 
constructing  reservoirs,  and  for  this  reason 
very  large  works  are  in  contemplation  and  in 
progress.  The  demand  for  water  is  growing  ; 
the  present  supply  is  limited  and  the  opinion 
is  held  that  the  increase  in  population  will 
eventually  render  resort  to  some  other  source 
than  the  Thames  watershed  imperative.  It, 
therefore,  is  necessary  to  provide  storage 
reservoirs  in  order  to  intercept  as  much  water 
as  possible  at  times  when  the  rivers  are  full ; 
but  there  is  another  very  important  reason 
why  a  policy  of  constructing  additional  storage 
reservoirs  has  been  adopted,  namely,  that  the 
\vater  in  the  Thames  and  Lea  is  of  such 
a  quality  that  it  requires  considerable  puri- 
fication, and  it  is  essential  to  do  everything 
possible  to  guard  against  harmful  germs, 
which  may  be  present  in  the  river  waters, 
finding  their  way  into  the  London  mains. 
That  the  measures  adopted  are  successful  can 
be  best  proved  by  practical  results,  inasmuch 
as  the  general  health  in  London  is  good. 

Dr.  Houston,  the  Board's  Director  of  Water 
Examinations,  reported  to  the  Board  to  the 
effect  that  bacteriologists  were  agreed  that 
pathogenic  microbes  do  not  multiply  in  storage 
reservoirs,  but  gradually  lose  their  vitality. 
The  time  required  to  effect  the  destruction  of 
these  bacteria  is  a  matter  of  controversy.  Each 
day's  storage,  however,  makes  for  safety,  and 
if  the  water  is  stored  for  a  sufficient  period 
the  subsequent  filtration  is  only  required  to 
improve  the  chemical  and  physical  qualities 
of  the  water.  Sand  filtration  under  the  best 
conditions,  that  is,  after  a  scum  has  formed 
on  the  surface  of  the  sand,  has  been  found  to 
be  effective  for  the  removal  of  bacteria,  but  as 
this  scum  eventually  becomes  so  dense  that 
the  water  cannot  pass  through  it  at  the 
required  rate,  it  has  to  be  periodically  cleaned 
off.  Thus,  the  action  of  the  sand  filter  alone 
is  not  to  be  relied  on. 

Under  these  conditions  it  is  obviously  desir- 
able to  store  water  for  as  long  a  time  as 
possible  ;  it  is  believed  that  danger  to  health 
by  over-storage  is  impossible. 


272 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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The  water  in  the  Thames  and  Lea  would  be 
utterly  unfit  for  drinking  purposes  were  it 
not  for  the  fact  that  the  river  authorities 
take  certain  precautions  against  dangerous 
contamination.  The  work  of  the  river 
authorities  has,  therefore,  a  most  important 
bearing  upon  the  London  water  supply. 
These  rivers  forming  as  they  do  the  only 
possible  drainage  channel  of  their  respective 
watersheds  must  necessarily  receive  the  whole 
of  the  sewage  of  the  population  above  the 
waterworks  intakes.  Everything  possible  is 
done  to  make  local  authorities  and  private 
persons  purify  sewage  to  a  high  chemical 
standard  before  it  is  discharged  into  the  rivers, 
and  this  purification  and  the  subsequent  large 
dilutim  in  the  river  combined  with  natural 
purification  in  the  stream  has  hitherto  suf- 
ficed. The  problem  is,  however,  a  very  serious 
one  owing  to  the  increase  of  the  population 
discharging  sewage,  and  to  the  increase  of  the 
population  requiring  a  supply  of  water. 

It  is  practically  impossible  to  say  what  is  the 
ultimate  supply  of  water  available  for  London 
as  gaugings  taken  on  the  river  weirs  do  not 
take  proper  account  of  the  enormous  quantity 
of  water  flowing  down  the  river  valleys  in  time 
of  floods ;  neither  do  they  take  into  account  the 
subterranean  flow  which  is  probably  consider- 
able. However,  some  idea  may  be  obtained 
from  the  gaugings  taken  at  Teddiugton  Weir 
on  the  Thames  and  at  Fieldes  Weir  on  the 
Lea  below  the  waterworks  intakes.  Presum- 
ably in  times  of  flood  accurate  gaugings  are 
impossible  as  the  weir  sluices  must  be  open 
and  the  floods  may  extend  beyond  the  river 
banks.  Disregarding  these  by  no  means  un- 
important facts  we  find  that  gaugings  taken 
in  the  year  ending  March  81,  1908,  show 
that  on  the  average  about  1,289,800,000  gallons 
per  day  flowed  over  Teddington  Weir  after  the 
WTater  Board  had  abstracted  their  supply. 

In  this  year  the  daily  quantity  abstracted 
from  the  Thames  was  122,600,000  gallons  or 
about  "0868  of  the  whole  flow. 

Similarly  in  the  case  of  the  river  Lea  in 
the  same  year  the  gaugings  at  Fieldes  Weir 
showed  that  78,800,000  gallons  of  water 


flowed  over  the  weir  on  the  average  per 
day  after  the  Board  had  abstracted  their 
supply,  which  was  on  the  average  45,100,000 
gallons,  or  about  "364  of  the  whole  flow. 
It  will  be  seen  that  the  proportion  of  water 
drawn  from  the  river  Lea  is  very  much  higher 
than  that  drawn  from  the  river  Thames. 
The  safety  of  the  London  consumer  with 
regard  to  the  purity  of  the  water  supplied  is 
guarded  by  the  vigilance  of  a  staff  of  chemists 
and  bacteriologists  who,  under  the  control  of 
the  Board's  Director  of  Water  Examinations, 
are  continually  testing  the  water.  In  the  year 
above  quoted  no  less  than  11,760  samples  of 
water  were  examined  either  chemically  or 
bacteriologically. 

With  regard  to  the  future  it  is  probable  that 
the  existing  sources  of  supply  will  continue 
to  be  used  for  some  time  to  come  owing  to  the 
enormous  works  which  would  be  required  in 
order  to  obtain  an  adequate  supply  from  any 
fresh  source.  It  has  been  proposed  to  obtain 
a  supply  from  Wales,  but  it  is  improbable 
that  this  vast  undertaking  will  commend  itself 
to  the  London  ratepayer  so  long  as  the  public 
health  remains  good  and  the  supply  of  water 
is  sufficient  in  quantity.  By  comparison  it 
would  be  far  more  economical  to  purify  all 
sewyage  entering  the  Thames  to  a  bacteriological 
standard  and  to  do  much  more  than  is  now 
being  done  to  prevent  river  pollution.  The 
natural  sources  of  supply  for  London  water 
are  to  be  found  in  the  rivers,  and  it  is  from 
every  point  of  view  desirable  and  essential  that 
these  rivers  should  be  kept  absolutely  pure. 
Much  unnecessary  pollution  which  is  easily 
preventable  now  takes  place.  Works  capable 
of  purifying  sewage  absolutely,  both  chemically 
and  bacteriologically,  can  be  and  are  being 
constructed  elsewhere ;  and  other  pollution 
of  various  kinds  can  be  reduced  to  a  mini- 
mum. With  such  remedies  possible,  it  is, 
therefore,  probable  that  the  Thames  and  the 
Lea  will  continue  to  be  the  sources  of  supply  for 
London.  Further  with  the  advance  of  science 
fresh  methods  of  purifying  water  are  coming 
into  use  which  will  be  available  as  a  further 
means  of  safety  when  required.  H.  C.  H.  S. 


M.S.E. 


273 


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ENCYCLOPAEDIA   OF 


MAN 


Lowcock  Sewage  Filter. — This  method, 
in  common  with  that  of  Waring  and  Ducat 
(see  "WARING  SYSTEM,"  and  "  DUCAT  FILTER"), 
depends  principally  upon  the  direct  oxidation 
of  the  sewage  by  strong  aeration.  The  Lowcock 
filter  contains  perforated  air-pipes  introduced 
at  15  in.  or  18  in.  down  from  the  surface  of 
the  filtering  material.  These  pipes  are  con- 
nected with  a  small  blower,  and,  the  top  of  the 
filter  being  sealed  with  a  layer  of  sand  and 
closely  packed  upper  layers  of  gravel,  the 
air  is  passed  downwards  and  out  with  the 
effluent.  In  the  "  Waring  system  "  the 
air  is  introduced  at  the  bottom,  and  the 
filters  are  aerated  upwards.  The  object 
in  both  cases  is  to  increase  the  efficiency 
of  the  filter  by  artificially  supplying  the 
air  necessary  for  the  support  of  aerobic 
bacterial  action.  The  air-pressure  used  is 
equal  to  a  4-in.  column  of  water.  The 
system  was  tried  at  Malvern  in  1892  with 
a  filter  of  sand  and  gravel,  and  later  at 
Wolverhampton  where  sand  and  coke  breeze 
was  used.  Lowcock  filters  3  ft.  6  in. 
deep  were  also  put  down  at  Tipton  in  1896, 
with  a  top  layer  of  fine  broken  limestone  and 
sand,  a  bottom  layer  of  coarse  coke,  the 
intermediate  portion  being  coke  breeze. 

Artificial  aeration  is  costly,  and  the  more 
recent  development  of  improved  methods  of 
distribution  and  natural  aeration  upon  per- 
colation beds  of  simple  and  uniform  con- 
struction throughout,  tends  to  show  that  the 
complications  necessarily  arising  from  systems 
involving  forced  aeration  and  heating  are  not 
required  for  the  production  of  a  good  per- 
manent effluent.  Experience  also  shows  that 
for  large  sized  works,  at  any  rate,  simplicity 
of  construction  and  adherence  to  natural  con- 
ditions are  essential  and  greatly  facilitate 
smooth  working. 

"  Made  Ground." — A  term  applied  to  land, 
such  as  a  building  site,  the  level  of  which  has 
been  raised  and  made  available  by  shooting  or 
tipping  surplus  earth,  and  debris  of  various 
kinds,  so  as  to  fill  up  hollows  and  irregularities 
of  surface,  or,  in  some  cases,  to  elevate  the 


surface  above  the  flood  level.  "  House  refuse  " 
is  often  disposed  of  by  tipping  upon  low  lying 
marsh-land  on  the  outsidrts  of  towns  as  is 
done  in  some  of  the  southern  and  eastern 
neighbourhoods  around  London.  The  owners 
of  such  otherwise  undesirable  sites  reap  a 
good  income  by  allowing  tipping  of  such 
material  including  builder's  refuse,  &c.,  at 
a  charge  of  a  few  pence  per  load.  Such 
"  made  ground  "  sites  often  ultimately  become 
"  eligible  building  plots  "  at  greatly  enhanced 
values,  but  the  practice  must  be  condemned 
upon  sanitary  grounds,  and  the  model  building 
bye-laws  of  the  Local  Government  Board  con- 
tain special  provisions  against  the  erection  of 
new  buildings  upon  insanitary  sites. 

Main     Drainage     of     Towns.  —  (See 

"  SEWERAGE.") 

Manchester  Sewage.— Experts' 
Report. — The  sewage  of  Manchester  origin- 
ally found  its  way  into  the  Irk  and  the 
Medlock,  thence  to  the  Irwell,  and  finally 
into  the  Mersey.  The  completion  of  the  Ship 
Canal  necessitated  some  method  of  treatment 
as  the  above-mentioned  rivers  became  the 
source  of  supply  to  the  Canal.  Works  for 
treatment  of  the  sewage  by  chemical  precipi- 
tation were  completed  in  1893.  (Sec  article 
"  MANCHESTER  SEWAGE  WORKS.")  It  was  recog- 
nised from  the  first  that  chemical  treatment 
would  be  inadequate,  and  originally  intermitten  t 
filtration  through  land  was  contemplated. 
The  area  which  would  be  required  was,  how- 
ever, soon  seen  to  be  very  large.  Under  the 
direction  of  Sir  Henry  Eoscoe,  experiments 
were  carried  out  with  small  niters  of  clinker 
and  coke-breeze  on  similar  lines  to  Mr. 
Dibdin's  experiments  at  Barking.  Favourable 
results  were  obtained,  but  owing,  among  other 
reasons,  to  apprehensions  <is  to  the  ultimate 
cost  of  artificial  processes,  a  scheme  was 
prepared  by  the  City  Surveyor  for  conveying 
the  effluent  to  the  upper  tidal  reaches  of  the 
Mersey,  the  discharge  to  take  place  at 
Randall's  Sluices,  a  short  distance  below 
Warrington.  The  scheme  met  with  strenuous 


MAN 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


MAN 


opposition  from  Warrington  and  Liverpool 
and  other  riparian  authorities,  and  was  finally 
rejected  on  a  poll  of  the  ratepayers  in 
Manchester.  The  City  Council  therefore 
resolved,  in  June,  1898,  to  appoint  a  com- 
mission of  experts  to  consider  the  whole 
question. 

The  commission  consisted  of  Mr.  Baldwin 
Latham,  engineer ;  Professor  P.  F.  Frank- 
land,  bacteriologist,  and  Professor  W.  H. 
Perkin,  Jun.,  chemist.  Under  the  direction 
of  these  gentlemen,  a  series  of  experiments, 
on  the  treatment  of  sewage  by  various 
methods,  was  begun  in  1898,  a  report  was 
issued  in  1899,  and  a  supplement  in  1900. 

In  addition  to  continued  observation  of  the 
results  obtained  from  the  experimental  beds 
started  by  Sir  Henry  Roscoe,  the  following 
lines  of  investigation  were  pursued  : — 

The  treatment  of  raw  sewage  by  single, 
double,  and  triple  contact  on  bacteria  beds ; 

The  treatment  of  settled  sewage  by  single, 
double,  and  triple  contact  on  bacteria  beds ; 

The  treatment  of  raw  sewage  by  means  of 
the  open  septic  tank  followed  by  one  or  more 
contacts  on  bacteria  beds  ; 

The  treatment  of  raw  sewage  by  means  of 
the  closed  septic  tank  followed  by  one  contact 
on  bacteria  beds ; 

The  treatment  of  storm-water. 

From  these  experiments,  it  was  con- 
cluded : — 

(1.)  That  the  bacterial  system  is  the  system 
best  adapted  for  the  purification  of  the  sewage 
of  Manchester. 

(2.)  That  the  bacterial  processes  are  best 
conducted  in  several  stages,  viz. : — 

(i.)  Settlement  and  screening  out  of  the 
grosser  solids. 

(ii.)  Anaerobic  decomposition  in  the  septic 
tank. 

(iii.)  Oxidation  on  bacteria  beds. 

For  thoroughly  satisfactory  purification 
more  than  one  contact  is  necessary  for  Man- 
chester sewage ;  but  the  experiments  showed 
that  the  area  of  secondary  beds  might  be 
considerably  less  than  the  area  of  primary 
beds. 


275 


As  a  result  of  these  experiments,  and  after 
consideration  of  methods  in  use  in  other 
towns,  a  complete  scheme  for  the  treatment 
of  Manchester  sewage  by  bacterial  methods 
was  proposed,  and,  with  modifications  made 
by  the  Local  Government  Board,  was  passed 
by  the  City  Council  in  September,  1900. 

G.  J.  F. 

Manchester  Sewage  Works. — DAVY- 
HULME  WORKS. — The  main  works  for  the 
disposal  and  purification  of  the  sewage  of  the 
City  of  Manchester  are  situated  at  Davyhulme, 
(Station  Urmston,  Cheshire  Lines  Railway) 
about  five  miles  from  the  centre  of  the  city. 

The  original  works,  which  first  came  into 
operation  early  in  1894,  were  designed  for 
the  treatment  of  the  sewage  by  chemical 
precipitation. 

The  new  works  for  bacterial  treatment  of 
the  sewage  were  completed  in  1904,  so  far  as 
to  permit  of  the  whole  of  the  flow  being  dealt 
with  in  tanks  and  primary  contact  beds. 

It  was  originally  intended  to  place  the 
second  contact  beds  on  land  at  Carrington 
and  Flixton  some  two  miles  from  Davyhulme. 
Land,  however,  has  been  acquired  in  the 
immediate  vicinity  of  the  present  works,  and 
powers  have  been  obtained  to  construct  the 
secondary  beds  thereon.  The  effluent  from 
these  beds  passes  direct  into  the  Manchester 
Ship  Canal,  without  any  final  treatment  upon 
land. 

The  land  at  Carrington  and  Flixton  is 
retained  in  the  possession  of  the  Rivers  Com- 
mittee of  the  Corporation  for  the  purpose  of 
future  extensions  should  they  at  any  time 
become  necessary. 

The  sewage  as  it  enters  the  works  passes 
through  a  system  of  screens  and  catch-pits, 
designed  to  intercept  coarser  floating  matter 
and  heavy  detritus.  The  flow  is  either  passed 
through  open  septic  tanks  on  to  the  half-acre 
primary  contact  beds,  or,  after  simple  sedi- 
mentation, on  to  the  storm-beds. 

The  sludge  which  deposits  in  the  sedi- 
mentation tanks,  or  which  accumulates  in  the 
course  of  time  in  the  septic  tanks,  flows  by 


T  2 


MAN 


ENCYCLOPEDIA   OF 


MAN 


gravity,  or  is  pushed  by  manual  labour,  into     for  private  wells,  &c.,  is  taken  at  21,000,000 


channels  leading  to  two  ejectors  from  which 
it  is  forced  under  air  pressure  into  two  storage 
tanks  near  the  banks  of  the  Ship  Canal  below 
Barton  Locks.  From  these  tanks  it  flows  by 
gravity  into  the  sludge  steamer  and  is 
deposited  at  sea  beyond  the  Mersey  Bar. 
Occasionally  a  portion  of  the  sludge  is  pressed 
and  disposed  of  among  neighbouring  farmers. 

There  are  four  sedimentation  tanks,  two  on 
each  side  of  the  central  roadway.  Each  of 
these  is  300  ft.  in  length,  100  ft.  in  width, 
with  an  average  depth  of  6  ft.,  containing  a 
volume  of  1,125,000  gallons. 

There  are  twelve  open  septic  tanks  with  a 
total  water  capacity  of  15,820,250  gallons, 
giving  approximately  a  time  of  flow  through 
the  tanks  of  15  hours  in  fine  weather. 

There  are  92  primary  contact  beds, 
covering  in  all  46  acres,  each  being  a  net 
half-acre  in  area.  Their  general  method  of 
construction  will  be  clear  from  the  following : 
The  beds  are  constructed  in  concrete  and  are 
filled  with  screened  clinkers  to  an  average 
depth  of  3  ft.  4  in.  The  bulk  of  the  filtering 
material  consists  of  fragments  from  2  in.  to 
J  in.  diameter.  Larger  clinkers  are  placed 
over  the  underdrains,  and  as  far  as  possible 
over  the  whole  bottom  of  the  bed. 

Clinkers  have  been  used  as  a  filtering 
medium,  as  experiments  showed  them  to  give 
the  best  results  from  the  point  of  view  of 
purification,  they  could  be  rapidly  and  cheaply 
obtained,  and  after  four  or  five  years  could  be 
taken  out  and  washed  at  a  cheap  rate,  so  as 
to  eliminate  the  softer  portions,  yielding 
eventually,  in  this  way,  a  hard  resistant 
material,  at  a  less  cost  than  material  of  equal 
quality  could  be  obtained  in  the  first  instance. 

There  are  27  acres  of  storm-beds  2  ft.  6  in. 
deep.  The  filtering  medium  is  unscreened 
clinkers,  well  underdrained.  The  beds  are 
designed  to  act  mainly  as  straining  filters, 
and  the  surfaces  have  to  be  scraped  from  time 
to  time. 

The  population  draining  to  the  works  is 
577,230.  The  strict  dry  weather  flow,  based 
on  the  water-supply  plus  certain  allowances 


gallons  per  day.  The  works  are  designed 
according  to  the  usual  Local  Government 
Board  requirements  on  this  basis.  The 
average  actual  dry  weather  flow  including 
sub-soil  drainage  is  approximately  27,000,000 
gallons,  and  the  average  total  flow  including 
storm-water  for  the  year  ending  March, 
1908,  was  36,700,000  gallons  per  day. 

The  sewage  contains  a  very  great  variety  of 
trade-effluents,  notably  ammonia  recovery 
liquors  (both  from  the  gas-works,  and  from 
private  manufacturers  of  snlphateof  ammonia), 
and  effluents  from  galvanizing  works  and  from 
dye-works.  Owing  mainly  to  these  effluents, 
the  composition  of  the  sewage  and  the  results 
obtained  by  the  septic  tanks  and  bacteria  beds 
are  not  comparable  with  corresponding  data 
for  works  dealing  only  with  domestic  sewage. 

It  has  been  found  possible  to  obain  a 
purification  of  from  70  %  to  75  %  by  means  of 
open  septic  tanks  followed  by  first  contact 
beds  operated  at  a  rate  of  upwards  of  120 
gallons  per  cubic  yard  per  day.  A  second, 
contact  bed  worked  at  the  rate  of  150  gallons 
per  cubic  yard  per  day  has  been  found  capable 
of  effecting  a  further  purification  of  from  65  % 
to  70%  on  the  first  contact  effluent  or  a  total 
purification  of  90  %  with  production  of  a  final 
effluent  which  is  uniformly  non-putrefactive. 

The  total  capital  expenditure  on  purification 
works  to  March,  1908,  including  the  cost  of 
the  original  works  for  chemical  precipitation, 
estimated  outlay  for  the  secondary  beds  now 
under  construction,  and  unused  land  at  Car- 
rington  and  Flixton,  amounts  to  £494,614  or 
17s.  per  head  of  population  served.  The 
average  annual  revenue  cost  of  treatment 
for  the  5  years  ending  March,  1908,  exclusive 
of  interest  and  sinking  fund,  amounts  to 
£19,310,  or  8d.  per  head  of  population. 

WITIIINGTON  WORKS. — These  works  serve  a 
population  of  60,000  situated  in  the  districts 
of  Withington  and  Levenshulme  with  an 
average  daily  sewage  flow  of  4,185,000  gallons. 

The  process  adopted  for  treating  the  sewage 
is  sedimentation,  followed  by  further  purifica- 
tion of  the  effluent  on  first  and  second  contact 


276 


MAN 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


MAR 


bacteria  beds.  There  are  two  detritus  tanks 
(capacity  83,400  gallons),  two  sedimentation 
tanks  (capacity  781,000  gallons),  ten  first  con- 
tact beds  (2,900  superficial  yards  each),  an 
equal  area  of  second  contact  beds,  and  a 
total  area  of  storm-beds  of  12,452  superficial 
yards. 

The  sludge  is  disposed  of  by  trenching  into 
land,  on  which  crops  of  various  kinds  are 
grown. 

The  sewage  is  purely  domestic  and  much 
diluted  by  sub-soil  water.  The  cost  of  actually 
treating  the  sewage,  apart  from  pumping  and 
refuse  disposal  charges  for  the  year  ending 
March,  1908,  was  ;£!  5s.  9d.  per  million  gallons 
or  7'84d.  per  head  of  population. 

Moss  SIDE  SEWAGE  FARM. — The  sewage  of 
the  suburb  of  Moss  Side  is  at  present  treated 
by  chemical  precipitation,  a  portion  of  the 
effluent  being  further  purified  on  land.  The 
amount  of  the  latter  is,  however,  inadequate, 
and  it  is  intended  to  divert  the  sewage  to  the 
main  works  at  Davyhulme  at  an  early  date. 

G.  J.  F. 

Manholes. — (See  "  SEWERAGE.") 

Mannesmann  Pipes.  —  Mannesmann 
weld  less  steel  spigot  and  faucet  pipes  for 
gas  and  water  mains  are  made  by  the  British 
Mannesmann  Tube  Co.,  of  London  Wall,  E.G. 
The  pipes  are  manufactured  in  lengths  up  to 
85  ft.  and  can  be  bent  cold  on  the  spot  if 
required .  The  advantages  claimed  for  this  class 
of  tube  include  saving  in  jointing,  labour,  and 
materials,  also  in  freight  and  transport  with 
immunity  from  breakage  in  transit  or  when 
laid.  The  pipes  are  specially  coated  with  the 
object  of  preventing  corrosion. 

Manometer. — A  general  term  applied  to 
instruments  for  indicating  the  intensity  of 
fluid  pressure.  These  are  more  commonly 
called  "pressure  gauges  "or  "vacuum  gauges," 
according  to  whether  the  pressure  to  be 
measured  is  above  or  below  that  of  the  atmo- 
sphere. The  simplest  and  most  accurate 
manometer  is  that  in  which  the  pressure  is 


caused  to  act  upon  a  balanced  column  of 
liquid  (mercury)  contained  in  a  glass  tube. 
The  displacement  of  the  mercury  increases 
with  the  pressure  and  tbus  affords  an  indica- 
tion of  its  intensity.  The  mercurial  gauge  is 
used  for  scientific  purposes,  and  as  a  standard 
for  testing  and  calibrating  ordinary  gauges. 
The  U-shaped  tube  containing  water,  em- 
ployed by  gas  engineers  and  others,  is  upon 
the  same  principle.  The  gauges  used  for 
ascertaining  the  pressure  of  steam,  air,  water, 
&c.,  in  practical  work,  are  nearly  always  of 
the  "Bourdon"  or  "Schaffer"  type.  'The 
mechanism  of  the  former  consists  of  a  curved 
metallic  tube  of  elliptical  cross  section ;  one 
end  of  this  tube  is  closed,  the  other  com- 
municates with  the  boiler,  condenser,  &c. 
Pressure  exerted  upon  the  interior  of  the  tube 
tends  to  change  the  elliptical  into  a  circular 
section  and  in  so  doing  straighten  the  tube 
and  cause  movement  of  its  free  end.  On  the 
other  hand,  if  the  pressure  inside  the  tube  is 
below  that  of  the  atmosphere  a  contrary  effect 
takes  place.  The  bending  action  of  the  tube 
is  transmitted  to  a  pointer  moving  over  a 
graduated  scale.  Jn  tbe  "Schaffer"  ^.auge 
the  pressure  is  applied  to  a  flexible  corrugated 
steel  diaphragm.  In  both  cases  a  quadrant 
rack  and  pinion  are  employed  to  amplify  the 
range  of  the  pointer.  E.  L.  B. 

Markets.  -  -  Acts  of  Parliament  —  Cattle 
Markets — Site— Pens  and  other  Departments — 
Markets  for  General  Merchandise — Eemoval  of 
Refuse. 

ACTS  OF  PARLIAMENT,  &c.  —  Markets  and 
Fairs  Clauses  Act,  1847;  Towns  Improvement 
Clauses  Act,  1847;  Public  Health  Act,  1875; 
Public  Health  (London)  Act,  1891;  Public 
Health  Act,  1908.  Public  bodies  are  em- 
powered to  provide  public  markets  in  their 
towns  or  districts  by  section  166  of  the 
Public  Health  Act,  1875,  which  states  :— 
"  Where  an  urban  authority  are  a  local 
board  of  improvement  commissioners,  they 
shall  have  power,  with  the  consent  of  the 
owners  and  ratepayers  of  their  district, 
expressed  by  resolution  passed  in  manner 


277 


MAR 


ENCYCLOPEDIA   OF 


MAR 


provided  in  Schedule  III.  to  this  Act,  and 
where  an  urban  authority  are  a  town  council 
they  shall  have  power  with  the  consent  of 
two-thirds  of  their  number,  to  do  the  follow- 
ing things,  or  any  of  them,  within  their 
district  :— 

"  To  provide  a  market  place,  and  construct  a 
market  house  and  other  conveniences,  for  the 
purpose  of  holding  markets ; 

"  To  provide  houses  and  places  for  weighing 
carts  ; 

"  To  make  convenient  approaches  to  such 
markets  ; 

"  To  provide  all  such  matters  and  things  as 


been  provided  and  a  large  square  in  the  centre 
of  the  town  laid  out  as  a  market  for  general 
merchandise. 

CATTLE  MARKETS  :  SITE. — The  site  for  a 
cattle  market  should  be  near  the  railway 
station  sidings,  so  as  to  avoid  the  harmful 
and  dangerous  passage  of  the  animals  through 
the  streets  of  the  town.  It  should  also  be 
near  the  public  abattoir  (if  there  is  one  pro- 
vided in  the  town)  for  exactly  the  same  reason, 
and  also  because  the  length  of  the  distance 
travelled  by  the  animal  makes  a  great  differ- 
ence in  the  weight  of  the  meat  after  killing. 
It  may  be  possible  to  provide  on  the  site  for 


^  *SS3^ 


Market  Buildings. 


may  be  necessary  for  the  convenient  use  of 
such  market ; 

"  To  purchase  or  take  on  lease  land,  and 
public  or  private  rights  in  markets  and  tolls 
for  any  of  the  foregoing  purposes  ; 

"  To  take  stallages,  rents,  and  tolls  in  respect 
of  the  use  by  any  person  of  such  market. 

"  But  no  market  shall  be  established  in  pur- 
suance of  this  section  so  as  to  interfere  with 
any  rights,  powers,  or  privileges  enjoyed 
within  the  district  by  any  person  without  his 
consent."  A  study  of  the  Model  Bye-laws, 
issued  by  the  Local  Government  Board  will 
also  prove  very  useful  and  instructive. 

Several  of  our  large  towns  liave  established 
markets  both  for  cattle  and  general  goods, 
whereas  in  smaller  towns  a  cattle  market  has 


the  erection  of  a  small  disinfecting  station,  and 
in  selecting  the  site  of  the  cattle  market  this 
should  be  borne  in  mind.  The  site  must  be 
well  drained,  as  far  away  as  possible  from  the 
inhabited  portion  of  the  town,  and  in  a  good 
open  quarter.  It  should  be  surrounded  by  a 
high  wall  and  have  several  entrances,  each  of 
large  double  gates.  These  may  be  either  of 
wrought  iron  or  wood.  Plenty  of  room  should 
be  allowed  in  the  market  for  the  easy  passage 
of  the  cattle  to  the  different  sections  and  pens, 
&c.,  provided ;  and  drinking  troughs  at  each 
entrance  and  in  other  convenient  places, 
several  in  number,  should  be  provided.  Water 
hydrants  should  be  provided  in  large  numbers 
to  flush  the  paving  and  floors  of  styes  and 
pens.  The  paving  of  the  site  will  be  a  matter 


278 


MAR 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


MAR 


requiring  careful  consideration,  care  being 
taken  to  provide  materials  which  will  have 
the  least  tendency  towards  slipperiness.  The 
whole  of  the  site  inside  the  enclosing  walls 
should  be  paved.  It  is  usual  to  provide  the 
following  accommodation,  but  the  needs  vary 
with  different  localities,  either  more  or  less 
being  found  necessary : — 1.  Pens  for  large 
cattle.  2.  Pens  for  stock  cattle.  3.  Pens  for 
cows  with  calves.  4.  Covered  pens  for  calves. 
5.  Pens  for  sheep.  6.  Covered  styes  for  pigs. 
7.  Stables  for  horses.  8.  Trotting  enclosure 
for  horses.  9.  Sheds  or  show-rooms  for  agri- 
cultural implements,  carts,  wagons,  &.c. 
10.  Ditto  for  seeds,  grain,  £c.  11.  Offices 
for  auctioneers.  12.  Weigh  office.  .  13.  Super- 
intendent's office  and  house.  14.  Rooms  or 
office  for  veterinary  surgeon.  15.  Waiting- 
rooms  for  drovers.  16.  Covered  sheds  for 
farmers'  wagons,  carts,  &c. 

This  list  is  merely  a  suggestive  one,  as  in 
some  districts  accommodation  for  other  pur- 
poses may  be  found  necessary.  In  addition 
to  the  above,  ample  lavatory  accommodation 
must  be  provided.  Before  dealing  with  the 
separate  sections  in  detail,  we  will  consider 
briefly  the  nature  of  the  paving  for  the  site. 
The  pens  and  lairs  should  be  paved  with 

(1)  granite  or  stone  setts  on  6  in.  of  Portland 
cement  concrete  ;   (2)  a  layer  of  asphalte  on 
concrete  ;  (3)  granitic  paving  laid,  in  situ,  and 
diagonally  scored,  to  allow  of  easy  draining, 
and   to   give   a   firm    foothold  to   the  cattle. 
These  will  be  found  to  lend  themselves  better 
for  cleaning  purposes,  besides  giving  a  foot- 
hold for  calves  and  pigs;  and  the  stables  for 
horses    may    be    paved    with    (1)  asphalte ; 

(2)  panelled  blue  bricks  on  6  in.  of  Portland 
cement  concrete  ;    or  (3)  granitic  paving  as 
above ;  all  laid  to  falls  and  effectively  drained. 
The  trotting  enclosure  for  horses  should  be 
paved  with  setts,  and  the  sheds  for  agricultural 
implements  and  farmers'  carts,  &c.,  should  be 
paved  with  asphalte  on  concrete  as  described 
above.     The  offices,  house,  and  waiting-rooms 
will  have  boarded  floors. 

1.  PENS  FOR  LARGE  CATTLE. — These  will 
include  pens  for  loose  cattle  and  pens  for 


tethered  cattle.  The  divisions  should  be  of 
iron  or  wooden  "post  and  rail  "  fences  about 
5  ft.  in  height.  Rings  for  tethering  the  cattle 
should  be  let  into  the  paving  about  4  ft.  apart. 

2.  PENS  FOR  STOCK  CATTLE. — These  should 
be  constructed  in  an  exactly  similar  manner. 

3.  PENS   FOR    Cows   WITH    CALVES.  —  These 
should  be  somewhat   larger    than    those   for 
cattle  as  above,  but  otherwise  will  be  similar. 
Sizes,  &c.,  are  given  later  on. 

4.  COVERED  PENS  FOR  CALVES. — These  will 
have  divisions  and  walls  constructed  of  brick. 
The  floors  should  be  raised  above  the  floor  of 
the  general  site  about  2  ft.  6  in.  or  3  ft.,  as 
these  animals  are  generally  brought  in  carts 
and  can  be  easily  transferred  to  or  from  the 
carts  if  the  floor  is  raised.     The  doors  may  be 
either  of  iron  post  and  rail  or  close  boarded. 
The  walls  should  be  about  3  ft.  above  the  floor. 

5.  PENS  FOR  SHEEP. — These  will    be   con- 
structed on  similar  lines  to  those  for  cattle, 
except  that  the  enclosing  fence  will  not  be  so 
high. 

The  paving  should  be  raised  from  the  front 
to  the  back  of  the  pen  in  a  gradual  incline,  to 
show  off  the  sheep  better. 

6.  COVERED    STYES    FOR  PIGS  will  be  con- 
structed on  exactly  similar  lines  to  those  for 
calves. 

7.  STABLES    FOR   HORSES,    fitted    up    with 
manger,   stalls,  &c.,    and   hay   loft,    harness 
room,  and  other  antechambers. 

8.  TROTTING   ENCLOSURE    FOR    HORSES. — A 
large  open  space   with   light   iron  post   and 
rail  fence. 

The  other  departments  are  of  the  usual 
type  and  need  not  be  described  here  in  detail. 
With  regard  to  the  sizes  of  pens,  &c.,  for 
cattle  and  other  animals,  the  Model  Bye-laws 
issued  by  the  Local  Government  Board  in 
1877  (which  upon  consultation  will  prove  very 
useful) ,  suggest  the  following  : — 

For  every  horse     .     .     .     8  ft.  by  2  ft. 

ox  or  cow  .     .     8  „   „   2  „ 
,,       mule  or  ass    .     5  ,,   ,,   15  ins. 

calf  .     .     .     .     5  ,,   „   15  „ 
,,       „       sheep,  goat,  or  pig  (of  medium 
size)  4  ft.  (superficial). 


279 


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If  these  dimensions  are  worked  to,  and 
inquiries  made  into  the  number  of  cattle 
likely  to  be  brought,  the  sizes  of  the  pens, 
&c.,  will  be  easily  found.  Large  boards 
with  the  names  of  the  various  sections 
painted  on  should  be  posted  up  over  those 
sections  to  enable  drovers  to  easily  find 
the  pens,  &c.,  for  their  different  cattle  and 
animals. 

MARKETS  FOR  GENERAL  MERCHANDISE.  — 
These  are  generally  buildings  of  an  imposing 
character,  and  are  treated  as  buildings  worthy 
of  architectural  beauty.  They  generally 
include  some,  or  all,  of  the  following  sec- 
tions : — 

Dead  meat  market.  Fish,  game  and  poultry 
market.  Fruit,  flowers  and  vegetables  market. 
Hardware,  ironmongery,  and  fancy  goods 
market.  Dairy  produce  market.  Grocery  and 
provisions  market.  Drapery  and  clothing 
market.  Public  conveniences.  Offices,  &c., 
for  market  superintendent. 

The  buildings  should  be  lofty,  and  prefer- 
ably all  sections  on  one  floor.  The  floors 
should  be  level  with  the  adjacent  streets,  and 
paved  with  impervious  paving,  e.g.,  asphalte 
or  granite  setts,  so  as  to  be  easily  washed 
down.  Gangways  should  be  constructed  in 
the  different  sections  for  vehicular  traffic,  the 
portions  between  being  raised  about  4  in. 
above  and  edged  with  granite  kerb.  Drainage 
should  be  very  carefully  considered,  and 
ventilation  and  light  must  be  plentiful. 
Standposts  must  be  placed  in  convenient 
positions,  and  should  be  plentiful  in  the 
meat,  fish,  game  and  poultry  sections. 

KEMOVAL  OF  REFUSE. — Large  manure-pits 
must  be  provided  for  the  cattle  market  to 
receive  all  manure  from  the  pens  and  styes. 
The  general  refuse,  dirt,  &c.,  may  be  swept  up, 
and  carted  away  immediately  to  the  refuse 
depot.  In  the  case  of  the  general  market, 
separate  bins  should  be  provided  for  refuse 
to  each  shop  and  stall,  the  contents  being 
removed  daily,  especially  in  case  of  the 
meat,  fish,  game  and  poultry,  and  vegetable 
sections. 

R.  H.  B. 


Mather  and  Platt's  Filters.  —  (See 
"  MECHANICAL  FILTRATION.") 

Mechanical  Filtration  (of  Water  Sup- 
plies).— The  mechanical  filtration  of  water 
for  purposes  of  public  supply  has  been 
practised  for  many  years  past  in  the  United 
States  of  America,  upon  the  Continent  of  Europe, 
and  many  other  places,  but  it  is  only  of  more 
recent  years  that  this  method  of  purification 
has  attained  any  considerable  foothold  in  this 
country.  There  is  no  doubt  as  to  the  efficiency 
of  the  more  generally  adopted  slow  sand- 
filtration  process  as  extensively  employed  for 
large  supplies  where  it  is  carried  out  under 
careful  supervision  and  control,  but  the 
capital  cost  of  such  filters  is  heavy  per 
million  gallons  filtered,  and  the  ground  space 
occupied  by  the  beds  is  large  compared  with 
the  more  intensive  and  compact  system  of 
mechanical  purification.  The  ordinary  gravita- 
tion sand  filter  for  efficient  filtration  does  not, 
as  a  rule,  pass  water  at  a  greater  rate  than 
from  18  to  20  gallons  per  square  yard 
of  surface  per  hour,  or  say  at  about  450 
gallons  per  square  yard  per  day  of  twenty- 
four  hours,  whereas  the  mechanical  filter  is 
capable  of  efficiently  treating  some  160  gallons 
per  square  foot  per  hour,  the  actual  speed 
of  filtration  in  any  given  case  depend- 
ing largely  upon  the  nature  of  the  crude 
supply  and  the  degree  of  purification  to  be 
obtained.  There  are  various  types  of  mechani- 
cal filters  in  use,  for  example  (1)  those  depend- 
ing on  straining  action  only ;  (2)  those 
combining  coagulation  and  subsidence  with 
straining  worked  either  as  gravity  filters  or 
under  pressure;  and  (3)  those  utilising  the 
oxidising  effect  of  the  imprisoned  air  by 
pumping  in  water  under  pressure  and  then 
taking  out  suspended  impurities  by  mechanical 
straining. 

In  the  United  States  of  America,  where 
river  and  lake  waters  are  largely  used,  there 
are  many  installations  of  the  Jewell  system  and 
other  mechanical  processes,  in  most  of  which 
a  coagulant  is  added  to  the  water  before  it 
passes  to  the  filter.  The  Alexandria  Water  Co. 


280 


MEC 


MUNICIPAL   AND    SANITAEY  ENGINEERING. 


MEC 


(Egypt),  has  adopted  the  system  of  the  Jewell 
Export  Filter  Co.,  of  New  York,  for  treating 
8,000,000  gallons  of  water  daily  from  the 
Mahmondieh  Canal,  which  is  in  direct  com- 
munication with  the  Nile.  In  England  the 
Jewell  filters  are  in  use  at  York  and  Wolver- 
hampton.  Some  of  the  leading  features  of  the 
filter  are  :  the  negative  head,  the  screen 


in  reinforced  concrete,  masonry,  steel  or 
wood. 

Other  systems  in  use  in  the  United  States, 
principally  for  the  filtering  of  turbid  river  or 
lake  water  are  the  "Hyatt,"  the  "  Loomis," 
the  "  Bowden,"  and  the  "  Duplex." 

In  England,  three  of  the  best  known  types 
of  mechanical  filters  are  the  Candy  oxidising 


FIG.  1. — Candy  Filters,  Cape  Town  Municipality. 


system,  the  uniform  rate  of  flow  and  automatic 
control  of  the  water  level  over  the  filter  bed, 
and  the  rate  of  filtration,  a  weir  around  the 
filter  tank  for  the  removal  of  the  dirty  wash 
water,  and  the  arrangement  of  valves  by  which 
the  working  of  the  filters  is  controlled.  Pre- 
vious to  passing  through  the  filters  waters  are 
subjected  to  coagulation  and  sedimentation. 
Iron  waters  are  treated  by  the  addition  of  lime 
followed  by  aeration  and  then  rapid  filtra- 
tion. The  filters  are  variously  constructed 


pressure   filters,    Mather  and  Platt's  gravity 
and  pressure  filters,  and  Bell's  filters. 

THE  CANDY  SYSTEM  (Figs.  1  and  2). — These 
filters  consist  of  steel  cylinders  of  the  form 
shown  in  the  illustration  and  into  the  upper 
part  of  which  water  is  pumped  under  pressure 
and  filtered  downwards  through  about  5  ft. 
of  filtering  materials  consisting  of  layers  of 
pure  silica  sandwiched  in  between  which  is  a 
layer  of  about  2  ft.  in  thickness  of  "  oxidium  " 
(see  "  OXIDIUM").  The  filters  are  of  special 


281 


MEC 


ENCYCLOPAEDIA   OF 


MEC 


service  in  the  removal  of  iron  from  waters 
used  for  public  supply,  whether  in  solution  or 
suspension ;  for  the  removal  of  peat  or  other 
discoloration,  and  also  for  the  removal  of 
organic  matters  and  bacteria.  The  principle 
upon  which  the  system  works  is  as  follows : — 
Water  is  either  pumped  through  the  filter,  or 


outlet  leading  to  clear  water  storage  reservoir. 
A  special  feature  of  the  system  is  that  when 
water  contains  iron  in  solution,  the  iron  is 
instantaneously  oxidised  and  thrown  into  sus- 
pension, so  that  it  is  readily  removed  by- 
passing through  the  bed  of  filtering  materials. 
The  pressure  under  which  the  filters  work 


Oxidium 

fcr  Ojcidixmy  and  Purifying 
83' 


Fine  Silica  Satid  and  Grtt 
fcr  Final  Filtration 


filtered  Water  Ccllec ticn  Chamber 


Fit;.  2. — Candy  Filter.     Section. 


passed  through  by  the  head  from  a  gravita- 
tion main,  which  upon  entering  compresses 
the  air  contained  within  the  filter  to  such 
pressure  as  may  be  arranged.  This  materially 
hastens  the  oxidation  of  iron  or  organic 
impurities  contained  in  the  water,  which 
subsequently  passes  downward,  through  the 
filtering  materials  above  mentioned,  to  the 


is  commonly  from  5  Ibs.  to  about  25  Ibs.  to 
the  square  inch,  but  this  is  a  matter  which 
must  be  adjusted  to  suit  the  particular  con- 
ditions and  water  under  treatment.  The 
process  of  oxidation  is  hastened  and  intensified 
if  atmospheric  air  is  pumped  into  the  filters 
by  a  small  auxiliary  air  pump,  as  is  done  at 
an  installation  of  these  filters  at  the  Tunbridge 


282 


MEC 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


MEC 


Wells  Corporation  Waterworks.  The  system 
is  used  for  the  public  supplies  of  the  corpora- 
tions of  Hastings,  Cardiff,  Newport  (Hon.), 
Merthyr  Tydvil,  Harrogate,  Tunbridge  Wells, 
by  municipal  authorities  in  South  Africa,  and 
by  a  number  of  water  companies.  The  results 
of  chemical  and  bacteriological  analyses  show 
the  system  to  give  an  effluent  of  a  high  degree 
of  purity.  A  filter  8  ft.  3  in.  diameter  is 
capable  of  dealing  with  from  8,000  to  9,000 


one-fourth  of  the  total  area  being  out  of  use. for 
cleansing,  whilst  in  the  case  of  mechanical 
filters  of  the  above  type  the  capital  cost  per 
1,000  gallons  effective  working  capacity  per 
day  amounts  to  between  cB3  and  .£4.  The 
working  expenses  in  connection  with  the 
mechanical  filters  is  found  to  be  about  Is.  per 
million  gallons  filtered,  as  compared  with  from 
3s.  to  5s.  per  million  gallons  with  sand  filtra- 
tion on  large  works.  In  the  case  of  small 


— *l 


11-  0 «U -  11  -  O  — 


FIG.  3. — Mather  and  Platt's  Pressure  Filters.     Plan. 


gallons  per  hour,  or  at  the  rate  of  160  gallons 
per  square  foot  per  hour.  The  filter  is  rapidly 
cleansed  by  simply  reversing  the  flow  of  water 
through  it  by  means  of  a  connection  to  the 
filtered  water  or  high  pressure  mains.  The 
quantity  of "  wash-water  "  required  varies  from 
•3  to  '7%  of  the  total  filtered,  according  to  the 
nature  of  the  crude  supply  dealt  with. 

The  relative  cost  of  mechanical  versus  sand 
filtration  depends  very  largely  upon  local  con- 
ditions, but,  under  ordinary  average  conditions, 
the  capital  cost  per  1,000  gallons  effective 
working  capacity  per  day  in  the  case  of  sand 
filters  may  be  taken  at  about  £15,  allowing  for 


works  sand  filtration  would  compare  much  less 
favourably. 

THE  MATHER  AND  PLATT  PRESSURE  FILTERS 
(see  Figs.  3  and  4). — These  consist  of  closed 
cylindrical  tanks,  with  sloping  sides  and  domed 
top  and  bottom,  supported  on  four  cast-iron 
legs.  The  larger-sized  tanks  are  made  of 
riveted  steel  plates,  and  the  smaller  sizes  of 
cast  iron.  Inside,  at  the  upper  part  of  the 
cylinder,  is  fitted  an  annular  channel  through 
which  the  unfiltered  water  enters  from  the 
inlet  valve,  over-flowing  the  edge  on  to  the 
bed  of  filtering  material,  and  passing  down 
through  it  to  the  collecting  chamber  at  the 


283 


MEC 


ENCYCLOPEDIA  OF 


MEC 


bottom.  The  filtering  material  consists  of 
quartz  crystals  in  graded  layers,  with  the  finest 
at  the  top.  From  the  illustration  (Fig.  4)  it 
will  be  seen  that  the  bed  rests  on  a  dished 
iron  plate  which  separates  the  filtering  and 
collecting  chambers.  A  considerable  number 
of  brass  nozzles  are  screwed  from  the  under- 
side into  the  dished  iron  plate,  ready  access 
being  obtained  by  means  of  a  door  fitted  in  the 
side  of  the  collecting  chamber,  so  that  they 


charge  valve  opened.  The  impurities  filtered 
from  the  water  collect,  mostly,  in  the  top  of 
the  bed,  and  in  order  to  facilitate  their  removal 
during  the  wash-out  a  rake,  which  can  be 
rotated  by  hand,  is  fitted  inside  the  cylinder, 
with  the  object  of  breaking  up  the  surface  of 
the  bed  during  the  cleansing  operation.  When 
the  water  from  the  wash-out  discharge  valve 
is  seen  to  be  clean,  this  valve  and  the  wash- 
out inlet  valve  are  closed  and  the  water  again 


mmm  -  ppf 

*"" 


FIG.  4.— Mather  and  Platt's  Pressure  Filters.     Section. 


may  be  replaced  without  disturbing  the  quartz 
bed.  The  object  of  these  nozzles  is  to  secure 
the  effective  use  of  all  parts  of  the  filtering 
bed  as  well  as  the  uniform  distribution  of  the 
water  used  in  washing  the  filter.  The  annular 
channel,  above  referred  to,  serves  to  spread 
the  unfiltered  water  over  the  bed  and  to  carry 
off  the  dirty  water  when  the  filter  is  cleansed. 
For  cleansing  the  filter  the  direction  of  flow  is 
reversed ;  the  unfiltered  water  inlet  valve  and 
the  filtered  water  outlet  valve  are  closed,  and 
the  wash-out  inlet  valve  and  wash-out  dis- 


admitted  through  the  unfiltered  water  inlet 
valve.  This  water,  however,  is  not  allowed  to 
pass  to  the  mains,  the  filtered  water  outlet 
valve  being  still  kept  shut,  but  instead,  the  re- 
wash  valve  at  the  bottom  of  the  filter  is  opened 
for  a  few  seconds  to  allow  the  first  discharge 
to  run  to  waste,  so  as  to  clean  the  nozzles  and 
collecting  chamber  of  any  dirt  which  may  have 
entered  with  the  wash-out  water,  and  to  settle 
the  upper  layers  of  the  quartz  bed  into  a 
properly  compact  condition. 

The  nitration  plant,  illustrated  in  Figs.  3  and 


284 


MEC 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


MET 


4  erected  in  1907  by  the  Bolton  Corporation  at 
Belmont  Road  reservoirs,  is  contained  in  a 
brick  building  80  ft.  by  40  ft.,  and  consists  of 
ten  filters  of  the  above  described  pressure  type, 
each  8  ft.  in  diameter.  The  plant  is  capable  of 
dealing  with  3,000,000  gallons  per  day  under 
a  working  pressure  of  200  ft.  head,  equivalent 
to  87  Ibs.  per  square  inch.1  These  filters  are 
arranged  in  two  rows  of  five  each,  the  rows  being 
spaced  16  ft.  apart  from  centre  to  centre,  and 
the  filters  placed  at  11-ft.  centres.  Between  the 
two  rows  of  filters  is  arranged  a  central  gallery, 
supported  by  iron  beams  carried  on  brackets 
attached  to  the  outside  of  the  filter  cases  ; 
from  this  gallery  the  whole  of  the  valves, 
agitating  rakes,  and  other  gear  can  be  worked. 
The  water  is  delivered  to  the  filters  through  a 
24-in.  main,  the  quantity  being  measured  and 
recorded  by  a  Venturi  meter  placed  in  one 
angle  of  the  filter  house.  This  main  extends 
in  a  trench  the  whole  length  of  the  house,  and 
alongside  it  is  a  second  24-in.  main  for  the 
filtered  water,  while  below  is  an  8-in.  pipe  to 
carry  off  the  wash-out  water  to  a  suitable 
outlet. 

BELL'S  FILTERS. — A  typical  installation  of 
this  type  of  pressure  filter  has  been  put  down 
at  Dunoon,  where  a  battery  of  twelve  filters  of 
8  ft.  diameter  each  are  in  use  for  treating  dis- 
coloured peaty  water  from  reservoirs  on  the 
bed  of  the  Balgie  Burn.  Each  filter  will  pass 
10,000  gallons  per  hour,  but  is  rated  at  a 
minimum  output  of  6,500  gallons  per  hour,  or 
78,000  gallons  per  hour  for  the  twelve.  At 
Dunoon  the  water  is  treated  chemically  before 
it  passes  to  the  filters.  This  treatment  con- 
sists in  adding  to  the  water  a  saturated  solu- 
tion of  lime  and  a  solution  of  alum,  varying  in 
strength  according  to  the  colour  of  the  water 
to  be  treated.  The  object  of  the  treatment  is 
to  remove  the  peaty  matter  to  which  the 
discoloration  is  due.  The  internal  arrange- 

1  The  installation  worked  at  this  rate  for  some  time 
removing  nearly  100%  of  suspended  matter,  but  as 
it  was  deemed  necessary  to  remove  the  peaty  stain 
and  bacteria,  sulphate  of  alumina  was  added,  and  the 
quantity  of  water  treated  daily  was  reduced  by  one 
half. 


285 


ments  and  mode  of  washing  these  filters  are 
described  by  Mr.  James  Andrew,  the  burgh 
surveyor  of  Dunoon,  as  follows  : — "  Each  filter 
contains  approximately  7  tons  of  fine  Leighton 
Buzzard  crushed  quartz,  on  the  top  of  which 
the  raw  water  descends.  There  are  144 
strainers  at  the  bottom,  conical  in  shape, 
with  detachable  perforated  lids  having  counter- 
sunk holes.  The  narrow  ends  of  the  strainers 
are  fixed  to  1-in.  pipes,  which  in  turn  are 
connected  to  a  series  of  3-in.  pipes,  the  3-in. 
pipes  again  connecting  to  the  filter  outlet. 
The  strainers  are  filled  with  pea  gravel,  and 
the  space  between  the  bottom  of  the  shell  and 
the  bottom  of  the  strainer  lids  is  filled  with 
concrete.  This  arrangement  at  the  bottom 
induces  the  whole  of  the  filtering  medium  to 
be  continuously  brought  into  action,  the 
inclination  of  the  water  to  descend  vertically 
being  no  greater  at  one  point  than  another. 
The  period  of  time  during  which  the  filters 
run  without  washing  depends  on  the  condition 
of  the  water,  and  intimation  "that  it  is  necessary 
to  wash  is  conveyed  by  the  gauge.  When  the 
water  is  at  its  be,st  washing  is  necessary  only 
once  in  three  days  ;  when  it  is  at  its  worst  it 
becomes  necessary  to  wash  twice  in  2 1  hours." 
Mr.  Andrew  also  states  that  '"  the  alumino- 
ferric  used  is  obtained  from  Messrs.  Peter 
Spence  &  Son,  of  Manchester,  and  costs  i'3 
per  ton  delivered  at  Dunoon  Pier.  The 
chemical  treatment  costs  on  an  average 
2s.  4d.  per  million  gallons  of  water  filtered. 
The  cost  of  treatment  for  labour  and  chemicals 
is  7s.  4d.  per  million  gallons.  The  total  cost, 
including  interest  and  repayment  of  capital, 
is  about  20s.  per  million  gallons." 

Metals  :  ALLOYS  are  not  merely  mix- 
tures of  different  metals,  they  partake  more 
of  the  character  of  solutions ;  were  they 
simple  mixtures  the  properties  of  the  com- 
pound would  be  the  mean  of  the  con- 
stituents, whereas  in  many  cases  new 
properties  are  developed.  The  structure  of 
alloys  has  been  most  satisfactorily  explained 
by  considering  that  different  metals  are  soluble 
in  each  other  in  different  proportions  under 


MET 


ENCYCLOPEDIA   OF 


MET 


different  states  of  concentration  and  at  different 
temperatures.  The  structure  of  steel  has  been 
very  thoroughly  worked  out,  and  it  has  been 
shown  that  it  consists  of  a  solid  solution  of 
carbon  in  pure  iron,  while  that  of  cast-iron  is 
explained  by  the  fact  that  the  amount  of 
carbon  soluble  in  the  molten  iron  is  so  great 
that  a  portion  separates  out,  as  graphite,  on 
cooling.  White  cast-iron  is  that  which  has 
been  cooled  suddenly,  so  that  the  carbon 
remains  in  chemical  combination,  not  having 
had  time  to  separate  out,  while  the  same  iron 
will  become  grey  cast-iron  if  cooled  slowly,  a 
small  portion  only  of  the  carbon  remaining  in 
chemical  combination  and  the  remainder  being 
present  in  mechanical  mixture.  The  most 
notable  alloys  after  iron  are  those  of  copper 
with  tin  and  zinc.  Bronze  is  a  mixture  of  about 
10  parts  copper  and  1  tin,  brass  is  a  mixture 
of  about  2  copper  and  1  zinc,  gun-metal  is  a 
mixture  of  about  16  copper,  2  tin,  1  zinc. 
Variations  in  the  proportion  of  the  constituent 
metals  produce  considerable  variation  in  the 
properties.  Some  of  the  principal  mixtures 

are : — 

BRONZE  ALLOYS. 


Name. 

Pumps  (very  tough) 
Pump  plungers 
Engine  bearings 
Heavy  bearings 
Hydraulic  valve  faces 
Valves  and  mountings 


Copper.  Tin.  Zinc.      Lead. 

3'2  3  1 

14  1  1 

112  13  i 

32  5  1 

4  1 

90  10  2i       — 


BRASS  ALLOYS. 


Name. 

Tough  for  engine  work 
For  turning  and  fitting 
Stop  cocks  and  valves 


Copper.  Zinc.  Tin.  Lead. 

.   100  15  15 

.3  1  ^ 

73  7  8  12 


SOLDERS. 

Spelter  for  brazing  (hard) .  . 
(soft)  .  . 
Tinmen's  fine  solder 

,,          coarse  solder 
Plumbers'  fine 


Alloys  are  used  for  various  purposes  with 
two  chief  objects  in  view,  firstly  to  reduce 
friction,  as  in  the  case  of  bearings  for 
machinery,  and  secondly  to  avoid  corrosion, 
as  in  pump  rams,  cocks,  bolts,  screws,  &c. 
The  simple  metals  used  in  forming  alloys  are 
non-corrodible,  but  some  of  them  are  too 


expensive  when  used  alone,  as  copper  or  tin, 
and  others  are  wanting  in  toughness,  as  zinc 
or  lead.  A  judicious  mixture  will  produce 
the  properties  most  desired.  Copper  is  the 
principal  ingredient  in  nearly  all  alloys,  its 
characteristics  being  modified  by  admixture 
as  follows.  Tin  increases  the  hardness,  and 
whitens  the  colour  through  various  shades  of 
red,  yellow,  and  grey.  Zinc  in  small  quantity 
increases  fusibility  without  reducing  the  hard- 
ness, in  greater  quantity  it  increases  the 
malleability  when  cold,  but  entirely  prevents 
forging  when  hot ;  1  to  2  %  of  zinc  enables 
sounder  castings  to  be  made.  Lead  increases 
the  ductility  of  brass,  and  makes  the  alloy 
more  suitable  for  turning,  filing,  &c. ;  in 
large  quantity  it  causes  brittleness.  Phos- 
phorus increases  the  fluidity  and  tenacity, 
reduces  the  effect  of  the  atmosphere,  arid 
allows  of  tempering  ;  it  also  produces  sounder 
castings.  For  brass  exposed  to  sea-water,  tin 
is  distinctly  preservative,  while  lead  and  iron 
are  both  injurious,  rendering  the  alloy  more 
readily  corrodible ;  the  percentage  of  the  two 
latter  metals  should  therefore  be  kept  as  low 
as  possible  in  all  brass  intended  for  purposes 
where  contact  with  sea-water  is  inevitable. 

H.  A. 

Meteorology. — Meteorology  is  that  branch 
of  science  which  deals  with  climate  and 
weather.  The  term  "Climate"  may  be 
defined  as  the  average  condition  of  meteoro- 
logical phenomena  at  a  given  place,  while 
under  the  term  "  Weather  "  may  be  included 
the  condition  of  the  atmosphere  at  any 
moment  with  regard  to  wind,  temperature, 
cloud,  moisture,  and  precipitation. 

INSTRUMENTS. — At  a  Climatological  station 
the  essential  instruments  for  making  meteoro- 
logical observations  are  only  a  Stevenson 
Thermometer  Screen,  containing  dry-bulb, 
wet-bulb,  maximum  and  minimum  thermo- 
meters, and  a  Snowdon  rain-gauge.  Some 
stations  have  in  addition  a  sunshine  recorder, 
a  grass  minimum  thermometer,  and  one  or 
more  earth  thermometers,  and  many  stations 
have  also  a  barometer.  Most  of  these  instru- 


286 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


MET 


ments  are  described   in   other   parts   of  this 
volume. 

TEMPERATURE. — The  "mean  temperature"  is 
usually  determined  by  adding  together  the 
readings  of  the  maximum  and  minimum 
thermometers  and  dividing  the  sum  by  2. 
The  "  range  of  temperature  "  is  the  difference 
between  the  readings  of  the  two  thermometers. 
The  range  is  greatest  at  inland  places  owing 
to  radiation,  and  least  on  the  coast,  where  the 
sea  has  a  moderating  effect  on  the  tempera- 
ture. On  July  22, 1868,  a  maximum  tempera- 
ture of  100' 5°  F.  was  registered  at  Tonbridge 
and  on  December  4,  1879,  a  minimum, 
temperature  of  -  -  23°  F.  was  registered  at 
Blackadder,  Berwickshire.  The  mean  tem- 
perature and  also  the  highest  and  lowest 
temperatures,  as  recorded  at  the  Royal 
Observatory,  Greenwich,  since  1841,  are  as 
follows  :  — 


Extremes. 

Months. 

Mean 
Temperature. 

Highest. 

Year. 

Lowest. 

Year. 

Deg. 

Deg. 

Deg. 

January 

08-6  F. 

57-OF. 

1843 

4-0  F. 

1841 

February 

39-5 

63-9 

1899 

6-9 

1895 

March 

41-9 

71-5 

1848 

13-1 

1890 

April 

47-3 

81-5 

1865 

23-0 

1847 

May 

53-1 

87-5 

1880 

28-1 

1877 

June 

59-4 

94-5 

1858 

35-6 

1869 

July 

62-7 

97-1 

1881 

38-7 

1863 

August 

61-6 

95-1 

1893 

38-1 

1864 

September 

57-2 

93-5 

1906 

30-6 

1885 

October 

50-0 

81-0 

1859 

24-7 

1890 

N  ovember 

43-5 

67-3 

1847 

18-3 

1890 

December 

39-9 

62-4 

1848 

8-0 

1860 

Year        .  .          49  -6 

97-1 

1881 

4-0 

1841 

The  isothermal  maps  of  the  British  Isles 
show  that  in  winter  the  highest  mean  tem- 
perature is  on  the  south-west  to  west  coasts, 
and  that  it  decreases  towards  the  north  or 
north-east ;  the  coldest  parts,  however,  are  the 
eastern  inland  districts,  while  in  summer  the 
inland  districts  are  the  warmest.  The  influence 
of  the  warm  water  of  the  Atlantic  is  shown  in 
a  very  marked  manner  by  its  effects  on  the 
west  coasts. 


MOISTURE.  —  The  quantity  of  water-vapour 
or  moisture  which  the  air  can  contain  is 
dependent  on  the  temperature.  The  air  at  a 
temperature  of  32°  F.  can  contain  2*13  grains  of 
water-vapour  ;  at  52°  F.  it  can  contain  4'39 
grains  ;  at  72°  F.  it  can  contain  8'27  grains  ; 
and  at  92°  F.  it  can  contain  15'74  grains.  Thus, 
the  higher  the  temperature  of  the  air,  the 
greater  is  its  capacity  for  moisture.  When 
the  full  capacity  of  the  air  for  vapour  has 
been  reached,  the  air  is  said  to  be  "  saturated." 
The  instruments  used  for  measuring  the 
amount  of  moisture  present  in  the  air  are  the 
dry-bulb  and  wet-bulb  thermometers  (see 
"  THERMOMETERS  ").  If  there  is  considerable 
difference  between  the  readings  of  the  two 
thermometers  it  indicates  that  the  air  is  very 
dry  ;  but  if  the  readings  are  almost  alike,  it 
shows  that  the  air  is  nearly  saturated  with 
moisture. 

By  means  of  Glaisher's  "  Hygrometrical 
Tables  "  the  dew  point,  the  elastic  force  of 
aqueous  vapour,  the  vapour  in  a  cubic  foot  of 
air,  the  relative  humidity,  and  the  weight  of 
a  cubic  foot  of  air,  can  be  worked  out  from  the 
readings  of  these  two  thermometers. 

CLOUD.—  When  the  air  is  cooled  below  the 
dew-point,  or  point  of  saturation,  the  moisture 
becomes  visible  in  the  form  of  cloud  or  fog. 
Much  information  on  the  conditions  prevailing 
in  the  upper  air  may  be  obtained  from  obser- 
vations of  clouds.  The  nomenclature  of  the 
different  modifications  and  forms  of  cloud,  as 
adopted  by  the  International  Meteorological 
Committee  is  as  follows  :  — 


Name. 

Cirrus  (Mare's  Tail) 
Cirro-Stratus 

Cirro-Cumulus  (Mackerel  Sky) 
Alto-  Stratus 
Strato-Cumulus 
Nimbus  (Eain  Cloud) 
Cumulus  (Woolpack  Cloud) 
Cumulo  -  Nimbus       (Thunder 

Cloud) 
Stratus 


Approximate  Altitude. 

27,000  to  50,000  ft. 

29,000  (average)  „ 

10,000  to  23,000  ,, 

10,000  to  23,000  „ 

6,500  (about)  ,, 

3,000   to  6,500  „ 

4,500   to  6,000  „ 

4,500  to  24,000  „ 
0  to  3,500 


287 


Some  idea  of  the  kind  of  weather  that  is 
likely  to  follow  may  be  formed  by  noticing  the 
type  of  cloud,  and  also  its  direction  and  rate 


MET 


ENCYCLOPEDIA   OF 


MET 


of   motion.     It  is  customary  to   observe  the     year  will  have  one-third  less  than  the  mean  ; 


proportion  of  sky  covered  with  cloud.  This 
is  done  by  estimation,  the  scale  adopted  being 
0  to  10,  0  indicating  a  cloudless  sky,  and  10  a 
sky  which  is  completely  covered  with  cloud  or 
overcast. 

BAIN. — Rain  is  produced  by  the  cooling  of 
the  air  ;  and  in  nearly  all  cases  this  cooling 
is  produced  by  the  expansion  of  the  air  in 
ascending  from  lower  to  higher  levels  in  the 
atmosphere.  The  rain  is  collected  in  a  rain- 
gauge,  and  the  water  measured  off  in  a 
graduated  glass  jar  in  hundredths  of  an  inch 
(see  "RAIN-GAUGE").  As  the  prevailing  wind 
in  this  country  is  from  the  South-west,  the 
air  comes  from  the  Atlantic  charged  with  a 
considerable  amount  of  moisture,  and  in 
striking  the  land  in  the  western  districts  it 
has  to  rise  until  it  reaches  the  highest  ground. 
In  doing  so  it  is  cooled  in  temperature,  and  so 
its  capacity  for  moisture  is  greatly  reduced, 
and  consequently  it  has  to  part  with  some  of 
its  moisure.  On  descending  on  the  eastern 
side  the  air  becomes  warmer,  and  having 
parted  with  a  considerable  amount  of  its 
moisture,  it  is  much  drier.  These  features  are 
brought  out  very  distinctly  on  reference  to  a 
Rainfall  Map  of  the  British  Isles.  It  is  at 
once  seen  that  the  western  parts  of  the 
country,  and  especially  the  hilly  districts,  are 
much  wetter  than  the  eastern  parts.  At 
Seathwaite,  in  Borrowdale,  Cumberland,  the 
average  yearly  rainfall  is  about  135  in. ;  while 
at  the  Stye  Head,  a  mile  from  Seathwaite,  the 
annual  rainfall  is  about  170  in.  The  driest 
district  is  over  the  eastern  counties,  where  the 
average  is  only  a  little  over  20  in.  According 
to  Dr.  H.  R.  Mill,  the  director  of  the  British 
Rainfall  Organisation,  the  average  rainfall 
over  the  whole  surface  of  the  British  Isles  is 
about  39|  in. ;  over  England  it  is  about 
32  in.,  over  Wales  49  in.,  over  Scotland 
47  in.,  and  over  Ireland  42'6  in. 

With  regard  to  the  limits  of  fluctuations  in 
the  total  rainfall,  the  late  Mr.  G.  J.  Symons, 
F.R.S.,  arrived  at  the  following  results  :— 
(1.)  The  wettest  year  will  have  a  rainfall  nearly 
half  as  much  again  as  the  mean ;  (2.)  the  driest 


(3.)  the  driest  two  consecutive  years  will  each 
have  one  quarter  less  than  the  mean;  and  (4.) 
the  driest  three  consecutive  years  will  each 
have  one-fifth  less  than  the  mean.  The  spring 
months  are  the  driest,  and  October  is  the 
wettest  month.  The  rainfall,  however,  is  very 
variable  from  month  to  month  ;  some  months 
may  have  6  in.  or  more,  while  others  may 
have  only  a  few  hundredths  of  an  inch,  and  so 
at  some  times  there  may  be  floods,  and  at 
other  times  droughts.  When  the  temperature 
is  below  the  freezing  point,  the  precipitation 
usually  takes  the  form  of  snow  (see  "  SNOW  "). 
Occasionally,  especially  in  thunderstorms,  the 
precipitation  takes  the  form  of  hail,  which  is 
frozen  rain.  Ordinary  hailstones  are  small, 
but  at  times  they  may  be  very  large.  Instances 
are  on  record  in  which  hailstones  as  large  as 
an  orange  have  fallen  in  this  country. 

THUNDERSTORMS. — Thunderstorms  are  small 
atmospheric  disturbances,  accompanied  with  a 
considerable  amount  of  electrical  energy,  which 
manifests  itself  in  the  form  of  lightning.  A 
lightning  flash  may  assume  various  forms ; 
sometimes  it  is  a  sinuous  wavy  line,  at  others 
it  has  a  number  of  branches,  and  occasionally 
it  appears  to  dart  all  over  the  sky.  Lightning 
is  liable  to  strike  exposed  objects  ;  so  it  is 
desirable  that  houses  and  buildings  should  be 
provided  with  efficient  lightning-conductors. 
Sheet  lightning  is  the  reflection  of  lightning 
taking  place  during  a  thunderstorm  at  a  con- 
siderable distance  away.  Instances  are  on 
record  of  lightning  being  so  seen  for  a  distance 
of  over  a  hundred  miles. 

Thunderstorms  are  usually  accompanied  by 
heavy  showers  of  rain,  and  sometimes  hail,  as 
well  as  by  a  squall  of  wind. 

SUNSHINE. — The  best  instrument  for  record- 
ing the  duration  of  sunshine  is  the  Campbell- 
Stokes  Sunshine  Recorder.  This  consists  of 
a  solid  glass  ball,  4  in.  in  diameter,  supported 
on  a  pedestal  in  a  metal  zodiacal  frame.  A 
card  is  placed  in  the  focus  of  the  ball,  and  on 
this  the  sun  burns  its  own  record.  The 
greatest  amount  of  sunshine  during  the  year 
is  recorded  along  the  south  coast,  and  the 


288 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


MET 


least  at  inland  places,  especially  in  the  neigh- 
bourhood of  manufacturing  districts,  where 
the  large  quantities  of  smoke  sent  into  the  air 
obstruct  the  sun's  rays. 

ATMOSPHERIC  PRESSURE. — The  changes  in 
the  weight  of  the  atmosphere  are  measured  by 
the  barometer  (see  " BAROMETER").  The  baro- 
metric pressure  has  a  variation  from  hour  to 
hour  during  the  day  which  is  most  marked  in 
the  tropics,  but  is  slight  in  the  British  Isles. 
This  variation  consists  of  a  double  minimum 
and  maximum,  viz.,  the  first  minimum  occurs 
about  4  or  5  a.m.,  and  the  first  maximum 
about  10  a.m.  The  second  and  more  pro- 
nounced minimum  takes  place  at  3  or  4  p.m., 
and  the  second  maximum  about  10  or  11  p.m. 
The  average  height  of  the  barometer  at  sea- 
level  in  London  is  29'955  in.  The  highest 
recorded  reading  in  the  British  Isles  was 
31'10  in.  at  Aberdeen,  on  January  31,  1902, 
and  the  lowest  27'332  in.  at  Ochtertyre,  near 
Crieff,  on  January  26,  1884. 

The  distribution  of  barometric  pressure  is 
readily  seen  from  isobaric  charts.  These  are 
prepared  by  plotting  on  a  map  the  barometer 
readings  reduced  to  sea-level,  and  drawing 
lines  through  those  places  which  have  the 
same  value.  These  lines,  which  are  called 
"isobars,"  will  then  represent  equal  barometric 
pressure.  It  will  at  once  be  seen  where  the 
pressure  is  highest  or  lowest.  The  areas  of 
high  pressures  are  called  "  anticyclones,"  and 
the  areas  of  low  pressure  are  called  "cyclones." 
If  on  these  maps  the  direction  of  the  wind  be 
also  plotted  by  means  of  arrows,  it  will  be 
noticed  that  the  arrows  fly  nearly  parallel 
with  the  isobars ;  round  the  areas  of  high 
pressure  they  move  in  the  direction  of  the 
hands  of  a  watch,  but  round  the  areas  of  low 
pressure  they  circulate  in  the  direction  opposite 
to  that  of  the  hands  of  a  watch.  This  applies 
to  the  Northern  Hemisphere.  In  the  Southern 
Hemisphere  the  directions  are  reversed  owing 
to  the  rotation  of  the  Earth. 

WIND. — The  direction  and  force  of  the  wind 
are  determined  by  the  distribution  of  baro- 
metric pressure.  As  the  pressure  for  the 
British  Isles  is  usually  lowest  in  the  north  or 


north-west,  and  highest  in  the  south  or  south- 
east, the  prevailing  direction  of  the  wind  is 
consequently  from  the  south-west.  This  is 
brought  out  very  clearly  by  the  following 
figures,  which  show  the  average  number  of 
days  in  the  year  on  which  the  wind  blows 
from  the  different  points  of  the  compass  at 
the  Greenwich  Observatory  : — 

N.      40  days.         S.E.      22  days.         W.      46  days. 
N.E.  45     „  S.          35     „  N.W.  22      „ 

E.      27     „  S.W.  106     ,,  Calm  22      „ 

For  particulars  as  to  observing  the  force  of 
the  wind  see  "  ANEMOMETER  "  and  "  WIND- 
FORCE." 

WEATHER. — If  the  observations  made  at 
various  places  at  the  same  hour  are  plotted 
on  maps,  they  give  a  very  good  idea  of 
the  distribution  of  actual  weather  over  a 
country  or  a  continent.  These  maps  are 
called  synoptic  weather-maps.  The  Meteoro- 
logical Office  compiles  daily  such  maps  for  the 
British  Isles  and  North-west  Europe,  for 
7  a.m.  and  6  p.m.,  and  upon  these  it  prepares 
forecasts  of  the  probable  weather  for  a 
period  of  24  hours  in  advance.  Storm 
warnings  are  also  sent  to  coast  stations  to 
give  fishermen  and  others  indications  of  the 
approach  of  storms. 

UPPER  ATMOSPHERE. — During  the  last  few 
years  efforts  have  been  made  to  obtain  infor- 
mation as  to  the  meteorological  conditions 
prevailing  in  the  upper  atmosphere  by  means 
of  kites.  The  Hargrave  box-kite  is  used  for 
this  purpose,  and  the  object  of  sending  it  up 
is  to  carry  a  meteorograph  for  recording  the 
pressure,  temperature,  and  humidity  of  the 
free  air.  Pilot  balloons  are  sent  up  for  deter- 
mining the  drift  of  the  upper  currents.  On 
specified  occasions  a  "ballon-sonde,"  carrying 
a  very  light  meteorograph,  is  also  sent  up, 
and  such  balloons  sometimes  attain  an  altitude 
of  as  much  as  14  miles  above  the  earth's 
surface.  The  interesting  point  brought  out 
from  the  records  obtained  during  the  ascents 
of  these  balloons,  is  that  the  temperature  of 
the  air  decreases  pretty  uniformly  up  to  about 
6  or  7  miles  above  the  earth,  but  beyond 
that  height  there  is  little  or  practically  no 


M.S.E. 


289 


MET 


ENCYCLOPEDIA  OF 


MET 


change,  and  in  fact  there  is  often  an  increase 
in  temperature.  W.  M. 

Meters,  Water. — (See  "  WATER  METERS.") 

Metric  System. — For  more  than  200 
years  attempts  have  been  made  to  secure 
a  system  of  weights  and  measures  which 
should  conform  to  the  decimal  system  of 
notation  in  use  in  arithmetic  all  over  the 
world,  and  should  unify  the  various  standards 
of  length,  weight,  area,  £c.,  by  building  them 
up  from  one  single  unit.  The  honour  of 
proposing  that  the  earth  itself  should  provide 
this  unit  belongs  to  the  Abbe  Mouton,  who 
published  the  proposition  in  1670.  It  was 
realised  during  the  first  French  Revolution 
mainly  because  the  prevailing  idea  in  France 
at  the  time  was  to  start  afresh  with  as  clean 
a  slate  as  possible.  This  reaction  found  ex- 
pression in  the  short-lived  alteration  of  the 
calendar  beginning  again  with  the  year  One, 
and  renaming  and  changing  the  primary  sub- 
divisions of  the  time  occupied  by  the  earth  in 
one  traverse  of  its  orbit.  What  is  of  more 
importance  is  that  the  new  measurements 
were  all  to  be  decimals,  thus  conforming  to 
the  ordinary  radix  of  notation  used  through- 
out the  civilised  world,  so  that  the  so-called 
"  compound  "  operations  so  puzzling  to  most 
people  and  so  wasteful  of  our  earlier  years 
should  no  longer  be  necessary.  As  early  in 
the  Revolutionary  period  as  1790  it  was  pro- 
posed to  realise  Mouton's  idea  by  measuring 
an  arc  of  10°  on  the  meridian  of  Paris,  say, 
10  or  11  miles,  to  calculate  therefrom  the 
quadrant  of  that  meridian,  i.e.,  as  much  of  it 
as  is  included  between  the  equator  and  the 
North  Pole,  and  to  employ  an  aliquot  part  of 
that  distance  as  a  unit  of  length,  and  not 
only  that,  but  as  a  unit  for  all  measurements. 
This  scheme  was  carried  into  execution  in 
1895.  The  arc  was  measured  by  the  usual 
surveying  methods.  In  other  words,  a  base 
line  was  actually  measured,  of  course  with 
rules  made  according  to  the  old  French 
methods,  and  triangulations  were  then  made 
from  the  base,  and  the  length  of  the  arc  was 
calculated  therefrom.  Fresh  calculations  gave 


the  quadrant,  one  ten-millionth  part  of  the 
result  thus  obtained  was  taken  as  the  new 
standard,  and  a  rod  was  made  of  that  length 
as  accurately  as  the  workmanship  of  the 
period  would  permit.  This  is  the  metre. 
One  unfortunate  misconception  must  here  be 
noticed  briefly.  Wonderful  as  it  may  seem 
now,  the  savants  to  whom  we  owe  the  ines- 
timable benefits  of  the  metric  system  were 
under  the  delusion  that  they  had  arrived  at 
an  indestructible  standard,  and  one  not  liable 
to  be  lost  by  any  accident  which  might 
happen  to  the  standard  rod  or  to  replicas  of  it. 
"  The  earth  is  our  standard,"  said  they, 
forgetting  that  if  a  thousand  remeasurements 
of  the  arc  were  made  they  would  all  be  different, 
and  hence  the  unit  derived  from  them.  This 
now  forgotten  mistake  detracts  in  no  way 
from  the  supreme  advantages  of  the  metric 
system.  All  measurement  depends  on  arbi- 
trary standards,  and  the  standard  metre  in 
Paris  is  just  as  arbitrary  and  unreproducible 
as  the  standard  yard  built  into  the  wall  at 
Westminster,  or  the  measures  on  the  north 
side  of  Trafalgar  Square.  There  is  no  such 
thing  as  "  absolute  measurement."  The  ad- 
vantages of  the  metric  system  may  here  be 
briefly  recapitulated: — 1.  It  is  a  decimal 
system,  conforming  therefore  to  all  arithmetic 
operations  by  decimals,  and  hence  workable 
in  arithmetic  without  any  compound  rules. 

2.  It    substitutes    one    standard     (arbitrary 
although   it   is   and    must    be)   for   different 
standards  ;  one  for  weight,  one  for  area,  &c.,  &c. 

3.  It  provides  a  means  for  unifying  measures 
geographically.     4.  It  refers  to  all  measures 
except  the  measures  of  time.     Decimal  time 
has  been  often  suggested,  but  no  scheme  has 
been  considered  practicable. 

The  metric  unit  is  the  metre.  This, 
primarily  a  unit  of  length,  supplies  all  the 
other  units  :— 

Unit  of  length  :      metre. 

,,      weight :      gramme  :  the  weight  of  a  cubic 

centimetre  of  water  at  4°  C. 
,,      area:          arc:  ten  metres  square. 
,,      volume  :     cubic    centimetres,  decimetres, 

&c. 
, ,      coinage  :     franc,  five  grammes  of  solid  silver. 


290 


MET 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


MIC 


Before  giving  a  table  of  equivalents  between 
the  metric  and  the  British  systems  one  more 
point  calls  for  notice,  and  here  we  have  yet 
another  advantage  of  the  metric  system. 
Aliquot  parts  and  multiples  of  a  British 
standard  are  called  by  names  which  have  no 
reference  whatever  to  the  name  of  the  larger 
measure.  It  is  not  obvious  on  the  face  of  it 
that  a  foot  has  a  definite  relation  to  a  yard, 
or  a  gallon  to  a  cubic  inch.  In  the  metric 
system  it  is  managed  more  rationally.  Re- 
membering that  it  is  a  purely  decimal  system, 
it  is  easy  to  see  the  principle  governing  the 
nomenclature.  Aliquot  parts  are  denoted  by 
prefixing  Roman  numerals  to  the  name  of 
the  standard,  while  a  similar  use  of  Greek 
numerals  denotes  multiples,  thus  : — 

1  milligramme  =  y^^  gramme. 
]  kilogramme    =  1,000  grammes. 
1  hectare  =  100  acres. 

1  centimetre      =  T^7  metre. 


The  Greek  prefix  deka  is  little  used,  on 
account  of  its  resemblance  to  the  correspond- 
ing Latin  word  and  the  consequent  danger  of 
confusion. 

COMPARISON  OF  ENGLISH  AND  METRIC  MEASURES. 
(Also  see  note  at  end.) 

WEIGHT. — English  to  Metric. 
1  Ib.  av.  =    0*454  kilogramme. 
1  oz.   „    =  28-34  grammes. 

Metric  to  English. 
1  kilogramme  =    2-2046  Ibs.  av. 
1  gramme         =  15*432  grains. 

LENGTH. — English  to  Metric. 
1  foot   =         0-3408  metre. 
1  inch  =      25'4  millimetres. 
1  mile  =  1609-3  metres. 

Metric  to  English. 
1  kilometre  =    0-621  mile. 
1  metre         =  39'37  in. 
=    3-281  ft. 

AREA. — English  to  Metric. 
1  square  mile  =  2'59  sq.  km. 
1  acre  =  4046-84  sq.  metres. 

1  square  foot  =        0'0929  sq.  metres. 

Metric  to  English. 

1  square  km.      =  0-386  sq.  mile. 

1  hectare  =  2-47  acres. 

1  square  metre  =  10'764  sq.  ft. 
=     1-196  sq.  yds. 

=  1,560  sq.  in. 
1,000  sq.  cm.      =     155  sq.  in, 


VOLUME. — English  to  Metric. 

1  cubic  yard  =    0-7645  cubic  metre. 
1  cubic  inch  =  16'39  cubic  cm. 
1  gallon  =    4-54  litres. 

1  cubic  foot   =  28-32  litres. 

Metric  to  English. 
1  litre  =     1-76  pints. 

1  cubic  metre  =  35'31  cu.  ft. 
1  cubic  cm.       =    0'061  cu.  in. 

It  is  not  difficult  to  commit  the  following 
table  to  memory,  as — 

22  Ibs.        =  10  kilos. 
22  yards     =  20  metres. 
22  gallons  =  100  litres. 
220  gallons  =  1  cubic  metre. 

It  must  be  remembered  that  these  conver- 
sions are  only  approximately  correct,  although 
accurate  enough  for  all  practical  purposes. 
The  number  of  inches  in  a  metre  is  expressed 
by  a  figure  which  runs  to  many  places  of 
decimals. 


Micro-organisms  in  Sewage. — The  de- 
composition of  all  organic  matter,  either  of 
animal  or  vegetable  origin,  is  due  to  the 
action  of  bacteria,  and  as  sewage  consists  of 
such  matters  dissolved  and  suspended  in 
water,  it  swarms  with  these  micro-organisms, 
and  whether  it  is  allowed  to  putrefy  and  pro- 
duce volatile  bodies  with  a  most  offensive 
odour,  or  is  so  treated  as  to  render  it  clear 
and  odourless  and  incapable  of  undergoing 
putrefaction,  these  changes  are  due  to  the 
action  of  bacteria.  Crude  fresh  sewage  rarely 
contains  less  than  one  million  bacteria  per  c.c., 
and  generally  contains  several  millions.  These 
may  be  divided  into  two  classes,  the  aerobic 
and  anaerobic  ;  the  former  growing  freely 
only  in  the  presence  of  an  abundance  of  air, 
and  the  latter  only  thriving  where  air  is 
excluded.  The  essential  constituent  of  the 
atmosphere  which  accelerates  or  retards  the 
growth  of  these  bacteria  is  the  oxygen ;  and  as 
the  real  purifying  organisms  are  aerobic,  the 
necessity  for  a  free  supply  of  air  during  certain 
processes  of  sewage  purification  is  rendered 
evident.  Whilst  in  the  sewers  the  aerobic 
bacteria  have  commenced  the  work  of  decom- 
position, and  the  urea  found  in  urine  and  tho 
291  u  2 


MIC 


ENCYCLOPAEDIA   OF 


MIC 


more  readily  decomposible  nitrogenous  matter 
found  in  excretal  matter    have  been  broken 
down  with  the  production  of  much  carbonic 
acid  and  ammonia.     The  Micrococcus  urea  is 
probably  the  most  important  organism  pro- 
ducing  this   change.     If   now  the  sewage  is 
confined  in  a  closed  tank,  or  the  access  of  air  is 
in  any  way  prevented,  the  anaerobic  bacteria 
become   active,    and   acting   upon   the   more 
insoluble  portions  decompose  them  with  the 
production  of  gaseous  and  other  bodies  which 
are  more  or  less  soluble.     The  destruction  of 
cellulose,  the   chief  constituent  of  the  woody 
fibre  from  which  paper   is   made,  is  chiefly 
effected   under   anaerobic   conditions  by   the 
Bacillus  amyloba  cter.      If   the  sewage  is   too 
long  confined  putrefaction   sets  in,  with  the 
production  of  a  relatively  large  proportion  of 
sulphuretted   hydrogen   and    other    offensive 
products,    the    presence   of   which   not   only 
causes  a  nuisance,  but  actually  impedes  the 
action  of  the  aerobic  bacteria  at  a  later  stage 
of  the  process  of  purification.     Confinement 
in  a  closed  tank,  therefore,  should  be  suffi- 
ciently long  to  liquefy  the  maximum  amount 
of  insoluble  organic  matter  without  allowing 
the  putrefactive  bacteria  to  develop  sufficiently 
to  render  the  odour  of  the  liquid  decidedly 
offensive.     The  sewage,  septicised  or  not  sep- 
ticised,   is  in   all    cases   finally   purified    by 
certain    aerobic    bacteria,     usually     grouped 
together  and  called   "  nitrifying  organisms." 
The  changes  are  generally  believed  to  take 
place  in  two  stages.     In  the  first  the  various 
ammonia  compounds  and  derivatives  are  de- 
composed with  the  production  of  nitrites,  and 
these    acting    on   a   further   portion   of    the 
ammonia    and    its    derivatives    form    stable 
organic  compounds  and  give  rise  to  evolution 
of  gaseous  nitrogen.     In  the  later  stage  allied 
bacteria  effect  further  oxidation,  and  nitrates 
appear  in  the  effluent,  and    the  more  com- 
pletely the  action  is  effected  the  less  ammonia 
and  organic  matter  will  remain  in  the  effluent 
and  the  greater  the  amount  of  nitrates  which 
will  be  present.    The  bacteria  causing  typhoid 
fever  and  cholera  have  rarely,  if  ever,  been 
found   in   sewage.     Attempts   to   isolate   the 


former  from  the  sewage  of  a  hospital  contain- 
ing many  typhoid  fever  patients  resulted  in 
failure.  Searching  for  them,  however,  has 
been  likened  to  seeking  a  needle  in  a  stack  of 
hay,  but  when  introduced  in  laboratory  ex- 
periments their  presence  can  be  demonstrated 
without  any  great  difficulty.  If  the  results  of 
various  bacteriologists  are  to  be  trusted,  the 
typhoid  bacillus  lives  longer  in  sewage  than 
in  pure  water,  and  at  the  present  time  we  are 
not  in  a  position  to  say  that  any  bacterial 
system  of  purification  destroys  the  germs  of 
typhoid  fever  or  of  cholera,  though  there  can 
be  little  doubt  that  the  number  of  such 
germs  in  a  sewage  effluent  will  be  few  relative 
to  those  in  the  original  sewage.  Certain 
bacteria  appear  only  to  thrive  in  the  presence 
of  animal  matter  undergoing  decomposition, 
and  these  are  of  especial  importance,  since 
the  detection  of  the  pollution  of  potable  water 
by  minute  quantities  of  sewage  depends  en- 
tirely upon  the  isolation  from  the  water  of 
one  or  more  of  these  organisms.  Many  of 
these  bacteria  are  either  difficult  to  isolate  or 
difficult  to  identify,  or  occur  in  comparatively 
small  numbers,  hence  they  are  of  little  use  as 
an  index  of  pollution.  On  the  other  hand, 
the  Bacillus  coli,  the  Bacillus  enteritidis  sporo- 
genes,  and  the  various  streptococci  occur  in 
considerable  numbers,  are  fairly  easily  isolated 
and  identified,  and  their  presence  in  a  water 
can  be  ascertained.  Their  presence  not  only 
indicates  sewage  pollution,  but  from  the  num- 
bers it  is  possible  for  an  approximate  estimate 
to  be  formed  of  the  extent  of  the  contamina- 
tion. Klein  and  Houston,  in  examining  the 
London  sewage  at  Barking  outfall,  found  these 
organisms  in  the  numbers  following,  per  c.c. 
of  sewage : — 


Bacillus  coli  communis 
Streptococci     . 
Spores  of  bacillus  enteri- 
tidis sporogenes    . 


100,000  to  800,000 
1,000  to    10,000 

100  to      2,000 


There  are  many  varieties  of  the  Bacillus  coli, 
and  if  all  were  included  the  numbers  above 
given  would  have  to  be  considerably  increased. 
On  the  other  hand,  the  characteristics  of  the 


292 


MIC 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


MIC 


Bacillus  coli  communis  can  be  so  defined  as  to 
considerably  decrease  the  apparent  number 
found  in  sewage.  The  number  of  bacteria 
found  in  sewage  effluents  varies  enormously, 
but  apparently  those  which  do  occur  are 
typical  of  the  original  sewage.  The  numbers 
may  be  decreased,  but  the  proportions  of  the 
more  easily  recognisable  organisms  are  not 
markedly  altered.  An  effluent  may  be  quite 
satisfactory  from  the  chemical  point  of  view, 
yet  contain  hundreds  of  thousands  of  bacteria. 
These  can,  of  course,  be  reduced  enormously 
by  sand  filtration  or  by  passing  through  suit- 
able land.  Where  it  may  be  necessary  to 
remove  practically  all  the  bacteria,  as  when 
the  effluent  has  to  be  discharged  somewhat  near 
the  intake  of  a  waterworks  or  near  shellfish 
layings,  their  destruction  can  be  ensured  by 
the  action  of  very  small  quantities  of  chlorine, 
either  as  gas  or  in  solution,  or  as  "chloride  of 
lime  "  ;  and  as  the  excess  of  this  chemical  can 
easily  be  destroyed,  it  is  probable  that  this 
process  will  in  the  near  future  be  employed  in 
special  cases.  J.  C.  T. 

Micro-organisms  in  Water.  —  Strictly 
speaking  the  term  micro-organism  includes 
all  the  forms  of  animal  and  vegetable  life 
which  require  the  aid  of  a  powerful  lense  or 
of  a  microscope  for  their  identification,  and 
includes  forms  most  diverse  in  character,  but 
usually  it  is  limited  to  the  very  minute  fungi 
called  "bacteria"  (vide  section  on  "GERMS 
OF  DISEASE").  These  bacteria  are  of  para- 
mount importance,  since  they  are  the  only 
organisms  which  infest  all  waters  and  which 
are  capable  of  rendering  it  a  vehicle  of  infec- 
tion. It  is  doubtful  whether  any  natural 
water  is  free  from  bacteria.  They  are  found 
in  the  water  from  the  deepest  wells  and 
purest  springs,  though  in  limited  number, 
but  it  is  rare  to  find  less  than  ten  in  one 
cubic  centimetre  of  water  from  any  source. 
In  such  pure  waters  they  have  a  tendency  to 
multiply  somewhat  rapidly  if  the  water  is 
kept  twelve  to  twenty-four  hours  before  being 
examined,  and  especially  if  the  water  attains  a 
temperature  exceeding  50°  F.  At  lower 


293 


temperatures  growth  may  be  retarded  or 
prevented,  hence  in  sending  samples  of  water 
for  bacteriological  examination  it  is  advisable 
to  pack  the  bottle  in  a  box  containing  a  little 
ice.  In  waters  which,  when  taken,  contain 
very  large  numbers  of  bacteria,  the  opposite 
results  may  ensue,  the  number  present  con- 
tinuously decreasing.  In  pure  water,  only 
bacilli  (rod-shaped  bacteria)  are  found,  in 
impure  waters  cocci  (spherical  bacteria)  are 
occasionally  found.  As  bacteria  flourish  on 
damp  surfaces,  in  soil  and  in  impure  water, 
and  are  also  found  in  the  air,  obviously  they 
gain  admission  to  water  in  many  different 
ways.  Fortunately  very  many  are  unable  to 
live  long  in  this  medium,  especially  if  exposed 
to  light ;  others  may  live  for  many  days 
without  showing  any  marked  tendency  to 
increase  in  numbers,  whilst  others  appear 
to  find  in  water  their  normal  habitat  and 
may  live  in  it  for  an  indefinite  period,  their 
increase  being  probably  limited  only  by  the 
amount  of  nutriment  present  in  solution. 
Belonging  to  the  fungi,  they  can  only  grow 
and  multiply  when  the  water  contains  organic 
matter  in  solution,  and  as  pure  waters  contain 
an  infinitesimal  trace  of  such  matter  very 
few  bacteria  are  as  a  rule  found  therein. 
On  the  other  hand,  waters  rich  in  organic 
matter,  from  whatever  source  derived,  gener- 
ally contain  an  abundance  of  bacteria.  When 
bacteriology  was  in  its  infancy  stress  was 
laid  upon  the  relative  abundance  of  bacteria 
in  water  as  a  test  of  quality,  a  water  con- 
taining few  bacteria,  say  less  than  500  or 
1,000  per  cubic  centimetre,  being  classed 
as  good,  whilst  one  containing  5,000  and 
upwards  would  be  regarded  as  polluted. 
The  bacterial  contents  of  waters  from  divers 
sources  at  different  seasons  vary  so  enor- 
mously that  these  arbitrary  standards  can 
no  longer  be  accepted,  and  numbers  now 
are  only  regarded  as  of  primary  importance 
as  a  test  of  efficient  filtration.  The  standard 
suggested  by  Koch  as  an  indication  of  efficient 
filtration  was  the  presence  of  less  than  100 
bacteria  per  cubic  centimetre,  such  bacteria 
being  enumerated  from  the  colonies  growing 


MIC 


ENCYCLOPAEDIA   OF 


MIC 


on  nutrient  jelly  in  forty-eight  hours  at  a 
temperature  of  70°  F.  In  this  country  the 
same  number  of  colonies  is  accepted,  but  the 
growth  is  allowed  to  continue  for  three  days. 
This  frequently  makes  an  enormous  difference, 
as  slow-growing  bacteria  may  develop  no 
visible  colonies  in  two  days,  but  may  produce 
colonies  visible  in  three  days.  The  present 
standard  is  therefore  higher  than  that  sug- 
gested by  Koch.  Of  more  importance  than 
the  mere  numbers  is  the  nature  of  the 
bacteria  present.  Of  the  large  number  of 
species  found  in  waters,  there  are  certain 
varieties  which  are  rarely,  if  ever,  found  in 
really  good  potable  waters,  but  which  are 
almost  invariably  present  in  water  from 
moorland  surface  on  which  cattle  are  grazed, 
in  water  from  fertile  and  manured  lands,  and 
water  containing  sewage.  These  bacteria  are 
of  animal  origin  and  flourish  best  at  a 
temperature  approximating  to  that  of  the 
human  body,  whereas  the  true  water  bacteria 
grow  slowly,  if  at  all,  at  that  temperature.  If 
water  is  mixed  with  a  jelly  made  of  agar 
instead  of  gelatine,  so  that  it  will  withstand 
a  temperature  of  98°  F.  without  melting,  and 
incubated  for  twenty-four  hours,  the  true 
water  bacteria  do  not  multiply  with  sufficient 
rapidity  to  produce  visible  colonies,  whereas 
the  foreign  bacteria  produce  such  colonies, 
and  the  number  produced  serves  as  an  indica- 
tion of  the  quality  of  the  water.  As  a  rule 
pure  waters  produce  few  such  colonies,  whilst 
polluted  waters  produce  many,  but  for  reasons, 
difficult  as  yet  of  explanation,  this  test  alone 
cannot  be  relied  upon.  As  a  confirmatory 
test,  however,  it  is  of  considerable  value. 
The  bacteria  of  typhoid  fever  and  cholera  are 
those  most  chiefly  to  be  dreaded  in  water,  but 
it  is  only  on  very,  rare  occasions  that  they 
have  been  discovered,  even  when  outbreaks  of 
these  diseases  have  been  traced  to  their 
presence.  It  is  practically  useless,  therefore, 
attempting  to  isolate  them.  Moreover,  it  is 
far  more  important  that  the  possibility  of 
such  pollution  should  be  discovered,  since  it 
is  too  late  to  discover  them  when  present,  as 
their  presence  will  have  been  already  demon- 


strated by  an  outbreak  of  disease.  These 
bacteria  can  only  gain  access  to  water  with 
excrementary  matter,  and  the  presence  of 
such  filth  therefore  indicates  the  possibility  of 
specific  pollution.  Reference  to  the  article 
on  "  MICRO-ORGANISMS  IN  SEWAGE"  will  show 
that  recent  sewage  always  contains  certain 
bacteria  which  are  easily  isolated  and  identi- 
fied, and  which  never  occur  associated  save  in 
manurial  matter.  Unfortunately  they  occur 
in  the  excrement  of  nearly  all  mammals  and 
fishes  as  well  as  in  human  excrement,  so  that 
their  presence  does  not  always  necessarily 
indicate  contamination  of  a  dangerous 
character,  since  so  far  as  we  know,  animals 
do  not  suffer  from  typhoid  fever  or  cholera 
and  cannot  therefore  impart  those  diseases  to 
man.  The  bacteria  referred  to  are  the 
Bacillus  coli  communis  and  its  varieties,  the 
spore-bearing  Ifaci^s  cnteritidis  sporogenes,  and 
cocci  occurring  in  chains  (streptococci).  Fresh 
domestic  sewage  generally  contains  about 
1,000,000  bacillus  coli  in  a  cubic  centimetre 
and  from  10,000  upwards  of  the  other  micro- 
organisms mentioned.  If,  therefore,  water  is 
contaminated  with  one-millionth  part  of 
sewage,  the  pollution  can  be  easily  detected 
bacteriologically.  This  test  is  far  more 
delicate  than  chemical  analysis,  which  may 
fail  to  detect  one  part  of  sewage  in  1,000 
of  water.  Moorland  waters  and  springs  in 
fissured  formations  fed  from  moorlands  almost 
invariably  contain  the  Bacillus  coli  derived 
from  animals  of  various  kinds  found  on  the 
watershed,  and  wild-fowl  may  pollute  the 
water  of  a  large  reservoir.  As  a  rule,  how- 
ever, good  moorland  waters  do  not  yield  more 
than  one  Bacillus  coli  in  10  cubic  centimetres, 
and  this  standard  is  usually  accepted  for  such 
waters.  Deep  well  waters  come  under  a 
different  category  and  should  not  contain 
the  Bacillus  coli  in  25  cubic  centimetres, 
but  on  occasions  the  organism  is  found  in 
deep  well  waters  in  greater  relative  abundance 
although  no  possible  source  of  contamination 
is  discoverable.  If  present  in  very  small 
numbers  and  unassociated  with  streptococci 
and  the  spores  of  the  Bacillus  cnteritidis 


294 


MID 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


MOR 


sporogenes,  their  presence  has  probably  no 
significance,  but  if  these  bacteria  are  also 
found  associated  in  the  same  sample  the  pre- 
sence of  pollution  derived  from  manurial 
matter  may  be  regarded  as  decisively  proved. 
Other  bacteria,  such  as  the  Proteus  rulgaris, 
Bacillus  subtilis  and  Bacillus  mycoides,  are 
frequently  found  in  waters,  and  indicate  con- 
tamination by  impure  surface  water  or  dust, 
but  so  far  as  is  at  present  known  they  have 
no  special  significance,  beyond  emphasising 
the  necessity  for  careful  watchfulness  and 
supervision  over  the  source  of  supply. 

J.  C.  T. 
Middens.— (See  ''PRIVIES.") 

Mortar ;    Composition    and    Strength 

of. — Builder's  mortar  is  a  mixture  of  lime 
and  sand  or  other  gritty  substance,  such 
as  burnt  clay  or  clinker,  ground  to  a  fine 
powder,  the  proportions  usually  being  one 
volume  of  unslaked  lime  to  three  volumes  of 
sand  or  grit.  All  limes  are  not  alike,  and  the 
differences  between  them,  as  W7ell  as  those 
between  different  samples  of  sand  and  grit, 
have  given  rise  to  much  controversy  and 
misunderstanding.  The  various  limes  are 
known  as  (1)  fat  limes,  i.e.,  obtained  from  the 
best  quality  chalk,  limestone,  &c.,  and  con- 
tain from  90  to  nearly  100  °/0  of  chemically 
pure  calcium  oxide  (CaO) ;  (2)  feebly  hydraulic 
limes  such  as  greystone  lime,  which  contains 
about  80%  of  calcium  oxide;  and  (3)  strong 
hydraulic  limes,  such  as  the  blue  lias  lime, 
containing  about  60%  of  calcium  oxide.  The 
fat  limes  are  used  as  a  "putty"  for  interior 
walls,  &c.,  and  the  feebly  hydraulic  and 
strongly  hydraulic  limes  for  mixing  with  sand 
to  form  mortar  for  bonding  bricks. 

The  character  of  the  sand  and  grit  is 
equally  a  matter  of  importance,  and  care 
should  be  taken  that  this  is  either  good  clean 
sand  or  crushed  clinker,  free  from  earthy 
matter,  by  which  term  is  meant  unburnt  clay, 
garden  mould,  or  road  sweepings,  &c.  The 
presence  of  a  small  quantity  of  natural  clay 
in  a  sand  has  been  supposed  to  be  detrimental, 
but  recent  researches  have  demonstrated  that 


if  the  quantity  does  not  exceed  10%  by  weight 
of  the  dry  sand  a  decided  advantage  in  the 
resulting  strength  of  the  mortar  is  obtained, 
which  is  confirmed  by  the  analysis  of  numerous 
samples  of  Roman  mortars  collected  from  the 
London  Wall,  Allington  Castle,  and  other 
authenticated  ancient  structures  whose  walls 
have  stood  the  test  of  time.  For  instance, 
three  samples  from  Allington  Castle,  collected 
by  Mr.  W.  D.  Caroe,  F.R.I.B.A.,  near  Maid- 
stone,  circa  twelfth  and  thirteenth  centuries, 
contained  highly  ferruginous  clay  equal  to 
8'6%,  3-66%,  and  4'0%  respectively  in  the 
sand,  the  sample  containing  8'6%  having  a 
crushing  strength  of  144  per  square  inch,  and 
that  containing  3'66  %  90  Ibs.  A  sample  of 
mortar  collected  by  the  writer  from  the  Roman 
wall  under  Leadenhall  Market  in  the  presence 
of  the  City  Surveyor,  Mr.  Perks,  and  Mr.  Max 
Clarke,  F.R.I.B.A.,  was  found  to  contain 
3'62%  of  ferruginous  clay  calculated  on  the 
dry  sand,  and  had  a  crushing  strength  of  about 
164  Ibs.  per  square  inch,  one  piece  resisting 
even  500  Ibs.  per  square  inch.  These  results 
confirm  the  series  of  experiments  submitted  by 
the  writer  to  the  Royal  Institute  of  British 
Architects,  December,  1906. 

Two  especial  points  to  be  observed  in  the 
selection  and  use  of  lime  for  mortar  are :  (1)  that 
the  lime  should  have  been  well  burnt  to  drive 
off  all  carbonic  acid  and  thus  secure  the  whole 
of  the  lime  being  in  an  active  state;  and  (2)  that 
the  lime  should  be  thoroughly  slaked  before 
being  used.  In  order  to  ensure  this  it  is  the 
practice  of  the  best  builders  to  slake  the  lime 
for  a  week  or  more  before  use.  Unfortunately 
the  introduction  of  the  mortar  mill  has  had 
a  tendency  to  introduce  unslaked  lime  into 
the  mill  with  the  sand,  crushing  the  whole 
together  and  then  employing  the  resulting 
semi-slaked  lime  on  the  work  without  further 
delay.  Bye-laws  which  have  been  made  by 
local  authorities  have  specified  so  much  lime 
and  so  much  sand  or  burnt  ballast,  the  latter 
to  be  crushed  in  a  mill.  The  builder  naturally 
adds  the  two  together  accordingly,  and  the 
mortar  is  made.  In  one  case,  coming  under 
the  writer's  experience,  the  builder  being 


295 


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aware  that  the  lime  should  be   first  slaked 
dry-slaked  it,  and  instructed  his  men  to  use 
the  materials  in  the  proportions  laid  down  in 
the  >bye-]aws.     The  volume  of  slaked  lime  is 
greater  than  that  of  the  unslaked  lime,  the 
expansion  being  about  1  to  1J  or  If.     This 
was     overlooked,     and     consequently     each 
"shovelful"  contained  less  than  would  have 
been   the   case   if   the   lime   had   been   vised 
unslaked   in   accordance   with   the    bye-laws. 
This   oversight,  which   led  to  much  trouble, 
might  have  been  avoided  if  the  bye-laws  had 
been  sufficiently  explicit.     The  fineness  of  the 
sand  or  grit  has  considerable  influence  on  the 
resulting  strength  of  the  mortar.     A  coarse 
sand  requires  more  lime  than  a  fine  one  to 
yield  the  maximum  strength,  wrhich,  however, 
is  from  two  to  three  times  that  obtained  with 
the   finer    sand   and   normal    quantity    of    a 
given  lime.     This  difference  is  entirely  due  to 
the  nature  of  the  voids  in  the    sand  which 
must  be  thoroughly  filled  by  fine  sand  and 
grit,  clay,  or  an  excess  of  lime.     If  this  is  not 
done  there  is  a  lack  of  that  intimate  contact 
between   particle    and   particle    which   is    so 
essential    in    all    cases    where    strength    of 
adhesion  is  required.     In  the  case  of  three 
samples  of  mortar  made  with   sands  having 
23,  28,  and  40%  of  voids  respectively,  the 
crushing  strength  of  the  mortar  at  the  end  of  one 
month  was  154, 155,  and  70  Ibs.  per  cubic  inch 
respectively,  the  tensile  strength  falling  from 
41  Ibs.  per  square  inch  to  32  and  28  Ibs.  for  the 
respective  samples.     It  is  therefore  important 
to  ascertain,  in  all  cases  where  the  greatest 
strength  is  required,  the  percentage  volume 
of  voids  in  any  particular  sand  proposed  to 
be  employed.      The  most  simple  method  of 
ascertaining  the  voids  is  to  place  the  sand  in 
a  glass  cylinder  marked  in  separate  divisions 
up  to  200  measures.     Run  the  sand   in  its 
natural  condition  into  the  cylinder,  so  that 
when  shaken  down   into   its  naturally  com- 
pressed condition  it  measures  100  divisions. 
Then  remove  the  sand  and  fill  up  to  the  100 
mark  with  clean  water.     Now  gradually  pour 
the   sand   into   the   water  and   shake  down. 
Note  the  height  to  which  the  water  rises  and 


the  volume  the  sand  now  measures  under 
water.  The  total  volume  thus  measured, 
minus  the  sum  of  the  volumes  of  the  water 
taken  and  the  volume  of  the  sand  as  measured 
under  water,  gives  the  voids  in  terms  of 
percentage  volume  thus  :— 

Sand  taken    . .          . .          . .          . .     100     c.c. 

Water      „ 100       „ 

Volume  of  mixed  sand  and  water  =     163-7    ,, 
,,          sand  under  water          =       99*0    ,, 
Voids  equal  sand  under  water  plus  water        .  .      199'0 
Less  volume  of  mixed  sand  and  water  163'7 


Per  cent. 


35-3 


One  of  the  questions  requiring  an  answer 
from  the  analyst  is  that  of  the  original  com- 
position of  the  mortar  in  terms  of  volumes  of 
sand  and  grit  to  lime.  This  cannot  be  stated 
with  perfect  accuracy  unless  samples  of  the 
original  materials  are  available,  but  a  close 
approximation  may  be  made  by  the  physical 
examination  of  the  constituents,  for  which 
purpose  the  lime  is  separated  from  the  sand 
and  grit,  and  the  weight  of  the  latter  per 
cubic  foot  noted.  The  lime  in  the  absence  of 
definite  data  may  be  assumed  to  have  been 
greystone  lime  of  80%  CaO  and  weighing 
40  Ibs.  per  cubic  foot,  but  great  caution  must 
be  exercised,  as  considerable  variations  arise. 
The  weight  of  the  commercial  lime  thus  found 
has  now  to  be  increased  by  calculation  in  the 
ratio  of  the  weights  per  cubic  foot  of  the  lime 
to  that  of  the  sand  and  grit  which  has  been 
already  obtained.  Thus  1  cu.  ft.  of  lime 
weighing  40  Ibs.  will  have  the  same  volume  as 
that  occupied  by  90  or  100  Ibs.  of  sand  or 
grit,  as  the  case  may  be,  or  of  50  or  60  Ibs.  of 
clinker,  &c. 

The  following  illustrates  the  method  : 

Lime  (CaO)  per  cent.     .  .     5'71 
Equal  to  commercial  lime  )  „. 

of  80%  (CaO)  ..  J 

Sand  and  grit  per  cent. .  .   91-13 
Moist   sand   and   grit  as 

used 107-0 

Commercial  lime  to  moist  sand  and 

grit,  by  weight         7'15     :     107 

Commercial  lime  to  moist  sand  and 

grit,  by  volume         . .          .  .          . .   19'1       :     107 

or     ,  ..1:5-6 


107  X  715 
40 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


MOR 


If  the  lime  had  been  measured  as  dry 
slaked  lime  its  volume  would  have  been 
increased  in  the  ratio  of  1  :  '53,  so  that  the 
ratio  would  have  been  1'53  to  5'6  or  1  :  3'66. 

The  setting  of  mortar  was  ascribed  by  the 
late  Professor  Graham  to  the  fact  that  "  on 
drying  the  mortar  binds  the  stones  between 
which  it  is  interposed,  and  its  own  articles 
cohere  so  as  to  form  a  hard  mass  solely  by 
the  attraction  of  aggregation,  for  no  chemical 
combination  takes  place  between  the  lime  and 
the  sand,  and  the  stones  are  simply  united  as 
two  pieces  of  wood  are  by  glue."  "  From 
the  minute  division  of  the  silica  and  alumina 
in  hydraulic  mortar  their  combination  with 
lime  is  more  likely  to  occur  than  in  ordinary 
mortar.  Still  the  fixing  of  hydraulic  mortar 
seems  to  be  due  chiefly  to  the  fixation  of 
water  and  formation  of  a  solid  hydrate  like 
gypsum."  This  agrees  with  the  experiments 
of  the  writer  on  mortar  made  with  materials 
free  from  soluble  silica.  After  twelvemonths 
no  trace  of  soluble  silica  could  be  detected  as 
would  have  been  the  case  if  any  combination 
between  the  silica  and  the  lime  had  taken 
place.  This  result  agrees  with  analyses  of 
ancient  mortars  in  which  the  soluble  silica 
is  no  more  than  would  be  found  in  the  fresh 
mortar.  For  instance,  the  three  samples  from 
Allington  Castle  already  referred  to  contained 
only  1'20,  0'70,  and  1'00%  of  soluble  silica; 
whilst  that  from  the  London  Roman  Wall 
contained  only  0'30%.  In  many  cases  where 
pozzuolana  or  trass  has  been  employed  the 
soluble  silica  will  be  high,  and  this  fact  has 
doubtless  given  rise  to  much  misapprehension 
on  the  point. 

The  manner  of  slaking  lime  for  making 
mortar  often  receives  too  little  attention. 
According  to  Mr.  Clifford  Richardson,  slaking 
fat  limes  with  two  volumes  of  water  added  at 
once  is  the  most  advantageous  procedure, 
and  that  but  a  small  departure  from  these 
proportions  on  either  side  will  result  in 
forming  a  less  satisfactory  paste.  With 
poorer  limes  much  smaller  volumes  of  water 
should  be  used.  Clifford  Richardson  has 
arrived  at  the  following  general  conclusions : 


"  It  appears  that  fat  limes  should  be  slaked 
with  2'5  volumes  of  water,  added  at  once  in  a 
closed  box,  to  obtain  the  best  and  largest 
amount  of  good  paste  ;  and  with  this  three 
times  the  volume  of  the  lime  in  the  shape  of 
moist  sand  may  be  mixed  for  fine  work,  such 
as  pointing,  plastering,  and  in  places  exposed 
to  dampness,  and  that  five  volumes  of  sand  is 
not  too  much  for  ordinary  brick- work. 

"  The  amount  of  mortar  which  a  barrel  of 
lime,  of  average  weight,  under  the  same 
conditions  as  in  the  experiments,  would  yield, 


Parts  Sand. 

3 
4 

5 


Parts  Water. 

2-5 
2-5 
2-5 


Cubic  Feet. 

16-5 
20-6 

24-8 


or  4  cu.  ft.  of  lime  with  2'5  parts  of  water, 
and  four  volumes  of  sand  would  yield  22  cu.  ft. 
of  mortar  which,  according  to  authorities, 
is  sufficient  to  lay  1,000  bricks  in  ordinary 
brick- work  with  coarsely  drawn  joints.  With 
more  compact  work  one  barrel  of  lime  will  lay 
1,000  bricks.  A  barrel  of  poor  or  magnesian 
lime  will  not  yield  more  than  three-quarters 
of  these  quantities."  W.  J.  D. 

Mortuaries. — The  Public  Health  Act, 
1875,  provides  that  any  local  authority  may, 
and  if  required  by  the  Local  Government 
Board  shall,  provide  and  fit  up  a  proper  place 
for  the  reception  of  dead  bodies  before  inter- 
ment, and  may  make  bye-laws  with  respect  to 
the  management  and  charges  for  its  use  ; 
they  may  also  provide  for  the  decent  and 
economical  interment  at  charges  to  be  fixed 
by  such  bye-laws  of  any  dead  body  which 
may  be  received  into  a  mortuary.  Any  local 
authority  may  provide  and  maintain  a  proper 
place  (other  than  a  mortuary)  for  the  reception 
of  dead  bodies  during  the  time  required  to 
conduct  any  post-mortem  examination  ordered 
by  a  coroner,  and  may  make  regulations  with 
respect  to  the  management  of  such  place ; 
and  where  any  such  place  has  been  provided, 
a  coroner  may  order  the  removal  of  the  body 
to  and  from  such  place  for  carrying  out  such 
post-mortem  examination.  It  is  not  infre- 


297 


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ENCYCLOPEDIA   OF 


MUN 


quently  found  that  a  public  mortuary  forms 
part  of  the  municipal  disinfecting  station ; 
experience  has  shown  that  it  is  a  wise  course 
to  adopt,  as  it  is  often  found  necessary  to 
destroy  filthy  and  infected  clothing  taken  from 
an  unclean  body.  A  public  mortuary,  to 
which  is  attached  the  coroner's  court,  should 
comprise  a  mortuary  fitted  with  slabs  or 
receptacles  for  the  reception  of  dead  bodies, 
mortuary  for  infected  bodies,  post-mortem 
room,  with  a  store,  w.c.,  and  lavatory  adjoin- 
ing, viewing  lobby,  shell  store,  doctor's  room, 
attendant's  room,  and  the  coroner's  court. 
The  Battersea  Disinfecting  Station  and 
Coroner's  Court  is  a  well-arranged  building 
of  this  character.  In  the  construction  of  these 
buildings  the  principal  features  are — plenty 
of  light,  good  drainage,  and  perfect  ventilation. 
The  latter  is  of  the  utmost  importance,  there 
being  a  certain  amount  of  organic  matter 
given  off  from  bodies  which  lie  in  the  mortuary. 
In  the  construction  care  should  be  taken  to 
avoid  any  materials  which  will  harbour  dust 
or  dirt.  The  internal  walls  should  be  faced 
with  white  glazed  bricks,  and  the  floors 
covered  with  some  hard  substance,  the  inter- 
section of  the  floor  and  wall  being  rounded. 
The  doors  should  be  of  oak,  solid  panelled, 
and  the  ceilings  plastered  and  then  painted 
and  varnished.  The  post-mortem  room  should 
be  lighted  from  the  roof,  having  a  northern 
aspect.  It  should  adjoin  the  mortuary  so 
that  a  body  may  be  easily  removed  from 
one  apartment  to  the  other.  This  room 
should  be  fitted  with  a  vitreous  enamelled 
operating  table,  sinks,  and  lavatory.  On  the 
walls  a  sufficient  number  of  glass  shelves 
should  be  provided  for  the  storage  of  bottles, 
&c.  They  should  be  of  polished  plate  glass, 
fixed  clear  of  the  walls  on  vitreous  enamelled 
iron  cantilevers  built  into  the  wall.  The 
sinks  and  lavatory  should  have  a  good  supply 
of  hot  and  cold  wrater.  When  the  mortuary 
adjoins  the  disinfecting  station  the  supply  of 
hot  water  is  easily  obtained.  When  no  supply 
of  hot  water  is  obtainable,  then  suitable 
geysers  should  be  provided.  The  provision 
for  viewing  bodies  varies ;  in  some  cases  a 


small  apartment  is  arranged  adjoining  the 
mortuary,  into  which  the  body  is  removed ; 
in  other  cases  a  portion  of  the  mortuary  is 
formed  with  a  window  and  the  body  placed  on 
a  slab  immediately  in  front.  In  all  cases  the 
viewing  room  should  be  so  arranged  that  the 
jury  have  not  to  walk  any  great  distance  from 
the  coroner's  court  for  the  purpose  of  in- 
specting a  body.  The  coroner's  court,  which 
is  provided  in  connection  with  the  mortuary, 
should  be  within  easy  access  from  the  main 
entrance  to  the  building.  In  addition  to  the 
court,  waiting-rooms  should  be  provided  for 
the  convenience  of  witnesses  or  prisoners. 

A.  C.  F. 

Municipal  and  County  Engineers, 
Incorporated  Association  of. — The  Asso- 
ciation was  founded  in  1873  with  the  following 
objects  : — "  The  promotion  and  interchange 
among  its  members  of  the  knowledge  and 
practice  which  falls  within  the  department  of 
an  engineer  and  surveyor  engaged  in  the 
discharge  of  the  duties  imposed  by  the  Public 
Health  and  Local  Government  Acts."  The 
Association  has  for  its  objects  at  the  present 
day  (inter  alia) : — (1.)  The  promotion  of  the 
science  and  practice  of  engineering  as  applied 
to  the  health  and  improvement  of  countries, 
towns,  urban  and  rural  districts.  (%2.)  The 
promotion  of  the  professional  rights,  interests, 
powers,  and  privileges  of  county,  urban,  and 
rural  engineers,  the  improvement  of  the 
professional  status,  and  the  extension  and 
interchange  of  professional  knowledge  and 
practice.  (3.)  The  examination  of  persons  in 
engineering,  surveying,  building  construction, 
sanitary  science  and  works,  and  in  local 
government,  municipal  and  sanitary  law,  and 
the  granting  of  certificates  of  having  passed 
the  examination  in  the  above  subjects  to 
candidates.  At  its  inception  in  1873  member- 
ship was  .restricted  to  those  holding  chief 
appointments  as  engineers  and  surveyors  to 
local  authorities  ;  but  in  1886  a  class  of 
graduates  was  formed,  the  qualifications  for 
election  to  this  class  being  the  passing  of  the 
examination,  which  was  instituted  in  that 


298 


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MUNICIPAL   AND   SANITAEY  ENGINEEKING. 


MUN 


year.  This  was  followed  in  1901  by  the 
inclusion  of  "  Associates,"  elections  to  this 
class  being  made  only  from  professional  men 
occupying  assistantships  in  the  municipal 
engineering  profession.  Finally  a  class  of 
"  Associate-Members "  was  formed  for  pro- 
fessional men  holding  minor  chief  appoint- 
ments or  important  assistantships. 

In  1890  the  Association  applied  for  and 
received  the  sanction  of  the  Board  of  Trade 
to  its  incorporation  under  the  Companies' 
Acts,  and  county  engineers  and  surveyors 
became  eligible  for  full  membership. 

In  1905  a  schedule  of  educational  require- 
ments was  adopted  for  candidates  for  permis- 
sion to  sit  for  the  examination. 

1.472  candidates  have  been  permitted  to  sit 
for  examination,  of  whom  713  qualified  for 
the  Association's  testamur.  Members  pay  an 
entrance  fee  of  £1  lls.  Qd.,  and  an  annual 
subscription  of  £1  lls.  6rf.  Associate  mem- 
bers (excepting  those  holding  the  testamur  of 
the  Association,  who  pay  no  entrance  fee)  pay 
an  entrance  fee  of  i'l  5s.,  and  an  annual 
subscription  of  £1  5s.  Associates  (excepting 
those  holding  the  testamur  of  the  Association, 
who  pay  no  entrance  fee)  pay  an  entrance  fee 
of  £1  Is.,  and  an  annual  subscription  of  £1  Is. 
Graduates  pay  an  annual  subscription  of  15s. 
The  Association  holds  meetings,  when  pro- 
fessional papers  are  read,  and  periodically 
pays  official  visits  to  different  centres  in  order 
to  inspect  municipal  works  of  all  descriptions. 
Papers  read  are  published  in  the  annual 
"  Proceedings."  The  last  annual  report  states  : 
"The  Association  consists  of  8  honorary 
members,  818  ordinary  members,  78  associate 
members,  127  associates,  and  170  graduates, 
making  a  total  of  1,201.  The  Association 
publishes  quarterly  a  digest  of  law  cases, 
that  are  of  interest  to  the  municipal  engineer." 

T.  C. 

Municipal  Engineers,  Institution  of. 

—The  Institution  of  Municipal  Engineers  was 
founded  in  May,  1908,  with  the  object  of 
providing  a  body  representative  of  the  pro- 
fession of  municipal  engineering  in  all  its 


branches,  or,  to  quote  the  words  of  the  resolu- 
tion : — "  That,  recognising  the  great  possibili- 
ties of  an  '  Institution  of  Municipal  Engineers  ' 
in  the  widest  sense  of  the  term,  men  holding 
important  appointments  under  local  authori- 
ties, such  as  electrical  engineers,  gas  engineers, 
mechanical  engineers,  and  water  engineers, 
shall  be  eligible  for  election  to  membership  of 
the  Institution." 

A  most  important  feature  of  the  Institution's 
programme  is  the  appointment  of  district 
committees  in  specific  centres,  each  committee 
having  its  local  chairman  (who  is  ex-qfficio  a 
member  of  the  Council)  and  local  honorary 
secretary.  By  the  establishment  of  these 
committees  the  policy  of  the  Institu- 
tion is  determined  by  the  majority  of  its 
members. 

The  carrying  out  of  practical  work  being 
considered  as  the  most  important  qualification 
for  admission  to  membership,  no  examination 
is  necessary  precedent  to  membership.  It  is 
recognised,  however,  that  many  members  may 
desire  to  have  their  special  knowledge  of  some 
branch  of  municipal  engineering  tested,  and  it 
is  proposed,  therefore,  to  hold  examinations  of 
a  severely  practical  character,  for  which  certifi- 
cates will  be  granted,  in  the  chief  branches  of 
professional  work. 

It  has  been  decided  that  membership  of  the 
Institution  shall  be  announced  by  the  affixing 
of  the  letters  "  M.I.Mun.E."  to  a  member's 
name.  The  agnomen  is  not  intended  to 
afford  proof  of  anything  beyond  member- 
ship of  the  Institution.  A  diploma  of 
membership  is  granted  upon  election.  The 
Institution  publishes  a  quarterly  "  Journal," 
and  has  established  a  lending  library  of 
technical  works. 

The  offices  of  the  Institution  are  at  39, 
Victoria  Street,  Westminster,  London,  S.W. 

B.  W. 

Municipal  and  County  Engineers  and 
Surveyors. — The  term  "  Municipal  Engi- 
neer "  is  unknown  to  the  law,  but  it  has 
become  an  accepted  usage  to  denote  by  the 
term  "  Municipal  and  County  Engineers  and 


299 


MUN 


ENCYCLOPEDIA   OF 


MUN 


Surveyors  "  the  officials  who  are  responsible 
for,  speaking  broadly,  the  constructional  work 
carried  out  by  local  authorities.  Their  main 
duties  are  thus  of  an  engineering  character, 
although  they  have  also  much  work  to  do  of 
an  architectural  or  purely  administrative  type. 
They  are  known  to  the  law  as  "  surveyors  "• 
such  a  description  is  a  misnomer.  The  pro- 
fession of  a  surveyor  is  denned  in  the  charter 
of  the  Surveyors'  Institution  as  "  the  art  of 
determining  the  value  of  all  descriptions  of 
landed  and  house  property,  and  of  various 
interests  therein  ;  the  practice  of  managing 
and  developing  estates  ;  and  the  science  of 
admeasuring  and  delineating  the  physical 
features  of  the  earth,  and  of  measuring  and 
estimating  artificers'  work."  If  this  definition 
be  considered  it  will  be  seen  that  most  of  the 
multifarious  and  widely-divergent  duties  of  a 
municipal  surveyor  are  outside  the  province 
of  the  profession  of  a  "  surveyor  "  altogether. 
For  the  present  purpose  it  is  convenient  to 
speak  of  the  officials  dealt  with  as  "  Public 
Health  Engineers,"  and  it  should  be  remem- 
bered that  this  title  is  coined  for  the 
purposes  of  the  moment,  and  is  meant  to 
include  county  surveyors  and  the  engineers 
to  municipalities  and  to  borough,  urban  and 
rural  authorities. 

Public  health  engineers  hold  their  offices 
under  different  statutes  according  to  the  kind 
of  authority  by  which  they  are  appointed. 
The  county  surveyor  is  appointed  by  the 
county  council  under  their  general  powers. 
The  duties  of  this  official  are  mainly  con- 
cerned with  the  maintenance  and  repair  of 
main  roads  and  bridges,  and  he  is  a  direct 
descendant  of  the  surveyors  who  were  first 
appointed  under  the  Statute  of  Bridges  (22 
Henry  VIII.  c.  5),  by  which  it  was  enacted 
"...  that  the  same  justices,  or  four  of 
them,  within  the  limits  of  their  commissions 
and  authorities,  shall  also  have  power  and 
authority  to  name  and  appoint  two  surveyors, 
which  shall  see  every  such  decayed  bridge 
repaired  and  amended  from  time  to  time,  as 


often  as  need  shall  require.  .  .  ."  The  sur- 
veyor to  an  urban  authority  (i.e.,  a  corporation 
or  urban  district  council)  is  appointed  under 
section  189  of  the  Public  Health  Act,  1875.  The 
same  section  fixes  the  salary  as  such  amount 
"  as  the  urban  authority  may  think  proper," 
and  further  provides  that  the  surveyor  shall 
be  removable  by  the  urban  authority  at  their 
pleasure.  The  effect  of  this  section  is  that 
the  surveyor  is  removable  from  office  at  the 
pleasure  of  an  urban  authority,  whereas  a 
medical  officer  of  health  or  inspector  of 
nuisances  is  not  so  removable  without  the 
consent  of  the  Local  Government  Board. 
Inasmuch,  however,  as  the  nature  of  the 
surveyor's  duties  is  such  as  frequently  to  lead 
a  conscientious  official  into  collision  with  his 
employers,  and  the  effective  administration  of 
sanitary  legislation  eminently  requires  inde- 
pendent executive  officers,  it  would  appear  to 
be  highly  desirable  that  in  the  matter  of 
Government  protection  the  surveyor  should 
be  placed  on  an  equality  with  the  medical 
officer  of  health  and  inspector  of  nuisances. 

The  surveyors  to  rural  authorities  are 
appointed  under  section  190  of  the  Public 
Health  Act,  1875  ;  and  the  surveyors  to  the 
Metropolitan  borough  councils  hold  their  office 
under  section  62  of  the  Metropolis  Management 
Act,  1855. 

It  is  provided  by  section  192  of  the  Public 
Health  Act,  1875,  that  the  same  person  may 
be  both  surveyor  and  inspector  of  nuisances, 
but  the  Local  Government  Board  do  not 
generally  assent  to  a  combination  of  these 
offices  in  a  district  of  large  area  or  popu- 
lation. 

The  duties  of  a  public  health  engineer, 
though  they  vary  according  to  the  kind  of 
authority  which  that  official  serves  may, 
and  generally  do,  involve  responsibility  for 
branches  of  work  which  have  been  con- 
veniently tabulated  by  Mr.  H.  Percy  Boulnois, 
M.Inst.C.E.,  a  former  City  Engineer  of  Liver- 
pool, under  the  following  main  divisions  and 
sub-divisions : — 


300 


MUN 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


MUN 


ENGINEERING. 


BRIDGES 


SEWERAGE 


Gathering  Grounds 
Deep  Wells 


Water  Carriage 

1 

Dry  System 

1 
Disposal 

1  _ 
Partially 
Separate 
System 

WATER 

1 

Separate 
System 

Complete      Earth 
System      Closets 

i               1 
Tubs      Pails 

ROAD  MAKING 

1 

|             Irrigation 
Middens               1 
Filtration 
1 
Precipitation 

3tion                               Supply 

1 

I                        1 
Traffic         Macadam 

Eoad  Boiling 

1                          1 
Paving          Footways 

1 

srs                        1                        | 
I                     Constant      Intermittent 
ngs                      |                       | 
Pumping      Gravitation 

1                1                1                  1 
Stone      Wood      Asphalte     Bricks 

Setts 

PREVENTION  OF  FLOODS 


TRAMWAYS 

I 


STREET  LIGHTING 

I 


I 
Cable 


Electric         Steam         Horse 

ARCHITECTURE. 

BUILDING  SURVEYOR. 

I 


Compressed  Air 


Electricity         Gas 


Dangerous  Structures 
Safety  of  Theatres 


Inspection  of  Plans 


Streets  in  Progress 


Defects 


House  Drainage 


Buildings  in  Progress 
Factories 


CORPORATION  BUILDINGS 
I 


Municipal  Offices 
Police  Stations 
Fire  Stations 

1 
Artizans'  Dwellings 

Public  Baths 
1 
Mortuaries 

1 
Markets 

Abattoirs 

ELECTRICITY  ACTS 


LAW. 
LIGHTING  ORDERS  SANITARY  ACTS 


GAS  AND  WATER  ACTS 


Special  Acts  Bye-laws 

ARBITRATIONS 


CONTRACTS 


Oppositions  and 
Promotions 


Extension  of 
Boundaries 


L.  G.  B. 

Inquiries 


REMOVAL  OF  SNOW 


HYGIENE 


MISCELLANEOUS. 

SCAVENGING 

I 


Collection 


Disposal 


LANDSCAPE  GARDENING 

I  


ROAD  WATERING 


DISINFECTION 


Recreation 
Grounds 


Cemeteries 
301 


Parks 


MUN 


NIT 


QUANTITY  SURVEYING 


SURVEYING. 
FIELD  WORK 

Levelling 

ADMINISTRATION. 


VALUATIONS 


STAFF 

1 

CONTRACTS 

COMMITTEE 

1 

Tradesmen's 
Accounts 
1 

1 

Wages 

Statistics 

Reports 

1 
Records 

i 

Correspondence 


Except  in  the  rarest  instances  the  puhlic 
health  engineer  is  not  in  virtue  of  his  office 
entitled  to  superannuation.  By  the  Super- 
annuation (Metropolis)  Act,  1866,  however,  it 
is  provided  that  the  London  County  Council 
and  the  Metropolitan  borough  councils  may, 
at  their  discretion,  grant  to  any  officer  in  their 
service  who  shall  become  incapable  of  dis- 
charging the  duties  of  his  office  with  efficiency 
by  reason  of  permanent  infirmity  of  mind  or 
body,  or  of  old  age,  upon  his  resigning  or 
otherwise  ceasing  to  hold  his  office,  an  annual 
allowance  not  exceeding  two-thirds  of  his  then 
salary.  It  is  difficult  to  see  any  distinction 
for  the  purpose  of  superannuation  between  a 
poor  law  official  (who  is  entitled  by  statute  to 
a  pension)  and  a  municipal  official,  and  it  is 
to  be  hoped  that  the  claims  of  the  latter  will 
soon  be  recognised  by  Parliament,  especially 
as  private  Acts,  on  the  lines  of  the  Poor  Law 
Officers  (Superannuation)  Act,  1896,  have  in 
recent  years  been  secured  by  several  Metro- 
politan boroughs  individually. 

The  usual  method  of  entering  the  profession 
of  a  public  health  engineer  is  by  serving  a 
pupilage  of  at  least  three  years.  The  premiums 
vary  from  about  £75  to  £300,  according  to  the 
size  of  the  town  or  district  and  the  professional 
standing  of  the  engineer.  The  next  step  after 
pupilage  is  usually  an  appointment  as  "junior 
assistant,"  at  a  commencing  salary  of  £60  or 
£70  a  year,  and  after  intermediate  stages  have 
been  passed  an  appointment  as  chief  assistant 
should  be  secured  at  an  annual  salary  of  from 
£130  to  £250.  Finally  a  chief  appointment 
may  be  obtained,  the  salaries  varying  from  a 


small  sum  up  to  £1,000  or  £1,500  a  year 
which  is  given  only  in  the  largest  cities. 
Full  information  as  to  these  matters  will  be 
found  in  a  little  book  entitled  "  How  to 
become  a  Municipal  Engineer,"  by  J.  Free- 
bairn  Stow,  late  Engineer  and  Surveyor  to 
the  Uxbridge  Eural  District  Council. 

It  has  become  increasingly  necessary  in 
recent  years  that  the  pupil  or  junior  assist- 
ant should  pass  some  of  the  examinations  of 
the  recognised  professional  examining  bodies, 
e.g.,  The  Incorporated  Association  of  Municipal 
and  County  Engineers,  The  Institution  of 
Municipal  Engineers,  The  Insitution  of  Civil 
Engineers,  The  Sanitary  Institute,  The  Sur- 
veyors' Institution,  &c.  If  he  does  not  do  so, 
he  will  find  that  he  is  at  a  considerable  dis- 
advantage in  the  keen  competition  which 
invariably  takes  place  for  any  good  appoint- 
ment. 

Public  health  engineers  have  two  pro- 
fessional organisations :  The  Incorporated 
Association  of  Municipal  and  County  Engi- 
neers (q.v.),  and  the  Institution  of  Municipal 
Engineers  (q.v.).  E.  G.  T.  &.  G.  T. 

Nitrification. — In  a  sanitary  sense,  means 
the  complete  oxidation  of  the  nitrogen  in 
organic  matter  by  its  conversion  into  nitrate. 
The  process  naturally  occurs  in  stages,  (a)  fer- 
mentation into  ammonia ;  (1>)  nitrosification 
or  intermediate  oxidation  of  this  into  nitrite  ; 
(c)  nitrification  proper,  or  final  oxidation,  into 
nitrate.  The  reverse  change,  denitrification 
takes  place  often  when  aeration  is  deficient. 
Each  reaction  is  occasioned  by  different 


302 


NIT 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


OKI 


species  of  bacteria,  some  of  them  working  in 
symbiosis,  the  condition  when  two  or  more 
species  act  together  and  effect  decompositions 
which  neither  of  them  could  do  separately. 
Whenever  we  find  a  final  filter  acting  badly, 
from  deficient  aeration  or  other  cause,  the 
fault  is  at  once  indicated  by  the  appearance  of 
a  high  proportion  of  nitrites,  as  nitrosification 
is  not  nearly  so  difficult  a  process  to  manage 
as  the  nitrification  which  should  naturally 
follow.  The  organisms  causing  the  latter, 
notably  Omeliansky's  nitrobacter,  require  for 
activity  that  the  ordinary  sewage  organic 
matter  and  ammonia  should  have  been  con- 
siderably reduced,  hence  the  advantage  of  a 
filter  in  successive  zones  like  that  of  Scott- 
Moncrieff.  But  the  presence  of  humus 
colloids  appears  to  preserve  the  vitality  of 
nitric  organisms  as  it  does  in  soils,  so  that,  in 
an  effluent  which  is  properly  prepared  and 
well  aerated,  nitrification  can  often  be  encour- 
aged by  seeding  with  a  small  quantity  of 
fertile  garden  soil.  It  is  always  necessary 
that  a  base  should  be  present  to  combine  with 
the  acid  formed,  therefore  in  a  sewage  farm  if 
the  ground  be  devoid  of  lime,  it  must  be 
added.  Liquids  to  be  nitrified  must  not  be 
too  strong  or  too  alkaline,  and  large  quantities 
of  chlorides,  as  in  sea-water,  are  unfavour- 
able, while  iron  salts  assist  the  process. 
Darkness  is  advisable,  and  a  free  supply  of 
air  is  always  necessary  ;  in  unaerated  filter 
beds  a  large  quantity  of  carbonic  acid  accu- 
mulates and  nitrification  is  hindered.  It  is 
important  to  notice  that  at  the  same  time  as 
the  nitrogen  in  sewage  is  converted  into 
nitrous  and  nitric  acid,  the  dissolved  carbon- 
aceous matters  are  also  oxidised  into  carbonic 
acid,  giving  a  double  improvement.  The 
nitrates  and  nitrites  contain  "  available 
oxygen  "  which  by  the  process  of  denitriftca- 
tion  can  supplement  the  dissolved  oxygen  of 
a  stream  into  which  sewage  may  flow,  in 
oxidising  the  organic  matters.  Hence  in  the 
case  of  any  stream  and  (clear)  effluent,  if  we 
ascertain  the  respective  volumes,  and  the 
amounts  of  oxidised  nitrogen  and  organic 
carbon  (by  the  "  oxygen  consumed "  figure), 


we  shall  obtain  a  ratio  showing  what  volume 
can  be  discharged  without  fouling.  A  highly 
nitrated  and  well-aerated  effluent  can  actually 
improve  many  rivers,  and  in  irrigation  has  a 
strong  fertilizing  power.  (See  "  OXIDATION  OF 
SEWAGE.")  S.  R. 

Norton's  Tube  Wells. — (See  "  ABYSSINIAN 
WELLS.") 

Notification  of  Diseases. — (See  "  ZYMOTIC 
DISEASES.") 

Ohio  Water  Supply  and  Sewage  Dis- 
posal.— The  Ohio  State  Board  of  Health  was 
created  in  1886.  The  Board  was  given  the 
usual  general  powers  regarding  the  control  of 
epidemics  and  infectious  diseases.  It  is  com- 
posed of  seven  members,  one  being  appointed 
by  the  Governor  each  year.  The  Board  was 
also  given  advisory  powers  regarding  public 
water  supplies  and  sewerage ;  but  had  no 
absolute  authority  over  these.  In  1893,  at 
the  time  of  the  cholera  epidemic  at  Hamburg, 
when  some  cholera  cases  were  being  imported 
to  the  United  States,  the  Ohio  State  Board  of 
Health,  realising  the  importance  of  protecting 
the  public  water  supplies,  asked  the  legis- 
lature for  increased  authority  along  these 
lines.  As  a  result,  there  was  passed  in  1893 
the  following  law  :  "It  (the  State  Board  of 
Health)  shall  respond  promptly,  when  called 
upon  by  the  State  or  local  governments  and 
municipal  or  township  boards  of  health  to 
investigate  and  report  upon  the  water  supply, 
sewerage,  disposal  of  excreta,  heating,  plumb- 
ing, or  ventilation  of  any  place  or  public 
building  ;  and  no  city,  village,  corporation,  or 
person  shall  introduce  a  public  water  supply 
or  system  of  sewerage,  or  change  or  extend 
any  public  water  supply  or  outlet  of  any 
system  of  sewerage  now  in  use,  unless  the 
proposed  source  of  such  water  supply  or  out- 
let for  such  sewerage  system  shall  have  been 
submitted  to  and  received  the  approval  of  the 
State  Board  of  Health."  In  1908,  with  a 
view  to  perfecting  the  above  law,  it  was 
amended  by  the  legislature  to  read  as  follows  : 


303 


OHI 


ENCYCLOPAEDIA   OF 


OHI 


"  No  city,  village,  public  institution,  corpora- 
tion, or  person  shall  provide  or  install  for 
public  use,  a  water  supply  or  sewerage  system, 
or  purification  works  for  a  water  supply  or 
sewage  of  a  municipal,  corporation,  or  public 
institution,  or  make  a  change  in  the  water 
supply,  waterworks  intake,  water  purification 
works  of  a  municipal,  corporation,  or  public 
institution,  until  the  plans  therefore  have  been 
submitted  to  and  approved  by  the  State  Board 
of  Health.  No  city,  village,  corporation  or 
person  shall  establish  a  garbage  disposal  or 
manufacturing  plant  having  a  liquid  waste 
which  may  enter  any  stream  within  twenty 
miles  above  the  intake  of  a  public  water  supply 
until  the  location  of  such  garbage  or  manufac- 
turing plant,  including  plans  for  disposing  of 
such  liquid  waste,  is  approved  by  the  State 
Board  of  Health.  Whoever  violates  any  provi- 
sion of  this  section  shall  be  fined  not  less  than 
one  hundred  nor  more  than  five  hundred  dol- 
lars." Since  1893,  therefore,  it  has  been  neces- 
sary that  all  plans  for  new  projects  for  public 
water  supplies  or  sewerage  be  approved  by 
the  Board.  In  regard  to  works  in  existence 
previous  to  1893,  the  Board  has  had  until 
the  year  1908  no  jurisdiction,  except  to 
investigate  and  point  out  to  local  officials  any 
conditions  which  need  improvement.  In  1898 
legislation  was  enacted,  authorising  the  State 
Board  of  Health  to  establish  and  maintain  a 
laboratory  for  the  chemical  and  bacteriological 
examination  of  public  water  supplies  and  of 
sewage  effluents ;  in  addition,  pathological 
work  was  provided  for.  The  Board  was 
directed  to  annually  examine  and  report  upon 
the  condition  of  public  water  supplies.  About 
this  time  the  Board  also  established  an 
engineering  department  for  the  purpose  of 
making  careful  investigations  of  the  proposed 
water  supply  and  sewerage  projects  which 
came  before  it  for  consideration,  as  well  as  for 
studying  the  conditions  of  existing  works. 
During  the  years  1897  to  1902,  inclusive,  the 
Board  has,  through  its  engineering  depart- 
ment and  laboratory,  and  with  the  aid  of 
other  temporary  expert  assistance,  made  a 
detailed  study  of  the  watersheds  of  all  the 


principal  rivers  in  the  State.     One   or   two 
watersheds  were  taken  up  each  season.     These 
studies  included  an  investigation  of  all  sources 
of  pollution  both  from  cities  and  villages,  as 
well  as  from  factories.      All  sewerage  systems 
and  waterworks  were  examined  in  detail,  and 
the  population  using  such  works  were  deter- 
mined.    Chemical  analyses  of  the  rivers  them- 
selves were  made  at  regular  intervals,  and  the 
pollution    of   the    water,    in   many  instances, 
was  thereby  conclusively  demonstrated.     The 
results  of  these  investigations,  including  maps 
and  statistical  information,  will  be  found  in 
the   annual   reports   of    the    State   Board   of 
Health.     These    reports    afford    a   very  com- 
prehensive view  of  Ohio  conditions  as  regards 
stream    pollution.       Supplementary    to    the 
above    work,  stream    gauging    stations    were 
established  on  certain  rivers  ;    and  these  were 
later   maintained    for    several   years   by   the 
United  States  Geological    Survey,  under  the 
immediate  direction   of   the   engineer  of  the 
State  Board  of  Health.     Daily  gauge  readings 
and  records  of  discharge,  covering  periods  of 
from  six  months  to  three  years,  of  some  fifteen 
of  the  rivers  of  Ohio  are  now  available.     These 
have  been  of  great  service  in  studying  sewer- 
age problems  and  also  in  other  work.     During 
1905  the  Board,  acting  co-operatively  with  the 
Hydro-Economic  Division  of  the  United  States 
Geological   Survey,  made  a  detailed  study  of 
the  disposal  of  certain  industrial  wastes  which 
had  long  been  sources  of  complaint.     Much 
valuable  and  practical  information  was  gained 
in  regard  to  the  purification  of  dairy  refuse, 
woollen  mill  waste,  acid  iron  waste  from  tube 
works,  and  the  refuse  from  distilleries.     The 
work  on  this  last  was  especially  interesting, 
as    a    method    was    developed    whereby   the 
valuable  ingredients  in   the   refuse  could  be 
reclaimed  at  a  very  substantial  profit  to  the 
distiller.    In  1906,  on  account  of  the  increased 
responsibilities  of  the  Board,  due  to  the  many 
important    projects    for    water    supply    and 
sewerage    which    were    submitted    to    it   for 
approval,    the    legislature    made     a     special 
appropriation    to    enable    it    to    increase   its 
engineering  and    laboratory  force  sufficiently 


OKI 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


OIL 


to  make  a  detailed  examination  of  the  con- 
struction, methods  of  operation  and  efficiency 
of  all  existing  water  and  sewage  purification 
works  in  the  State.  This  special  investi- 
gation consisted  of  a  series  of  detailed  and 
systematic  examinations  of  all  the  water 
purification  and  sewage  purification  works 
in  operation  in  the  State  of  Ohio.  One  of 
the  assistant  engineers  devoted  his  entire 
time  to  the  water  purification  works  and 
another  to  the  sewage  purification  works. 
Each  examination  occupied  usually  two  or 
three  days,  during  which  time  a  large  number 
of  samples  of  the  raw  and  treated  sewage  or 
water  were  collected,  and  observations  made 
on  rates  of  filtration,  chemicals  used,  and 
upon  other  features.  The  bacterial  samples 
were  all  plated,  and  most  of  the  other 
analytical  work  done,  immediately  following 
the  collection  of  the  samples,  in  the  field. 
This  avoided  the  undesirable  feature  of 
shipping  the  samples  by  express,  and  thus 
added  a  great  deal  to  the  value  of  the  investi- 
gation. A  full  detailed  report  covering  the 
investigation  is  published  under  the  title, 
"  Report  of  an  Investigation  of  Water  and 
Sewage  Purification  Plants  in  Ohio,  1906 — 
1907."  The  investigation  above  described 
served  to  further  equip  the  State  Board  of 
Health  for  the  responsibilities  which  were 
placed  upon  it  by  the  legislature  in  the 
spring  of  1908.  In  April,  1908,  there  was 
passed  a  law,  known  as  the  Bense  Act,  con- 
ferring upon  the  State  Board  of  Health  the 
power  to  order,  in  each  case  with  the  approval 
of  the  Governor  and  Attorney-General,  any 
city,  village,  or  corporation  to  install  a  water 
or  sewage  purification  plant  whenever  it  is 
shown,  after  investigation  and  after  granting 
full  hearing  to  those  interested,  that  such  a 
plant  is  necessary.  Existing  works  may  be 
changed  or  enlarged  through  a  similar  pro- 
cedure. The  Act  further  empowers  the  State 
Board  of  Health  to  secure  competent  operators 
for  water  and  sewage  purification  plants.  If 
a  community  or  corporation  believes  that  any 
order  of  the  State  Board  of  Health  is  not  just, 
then  "  the  necessity  for  and  reasonableness  of 


such  order  "  may  be  submitted  to  a  commission 
of  referee  engineers  who  shall  have  power  to 
affirm,  modify,  or  reject  such  order ;  one  of 
these  referee  engineers  to  be  chosen  by  the  com- 
munity or  corporation  and  the  other  by  the 
State,  and  they  to  choose  a  third  if  necessary. 
The  decision  of  this  engineer  commission 
is  to  be  final.  In  this  way  a  municipality  or 
corporation  has  ample  protection  against  the 
possibility  of  arbitrary  or  unjust  orders,  thus 
removing  criticism  made  in  the  past  of  the 
placing  of  too  much  authority  in  the  hands  of 
a  State  Board  of  Health.  An  important 
feature  of  the  Act  and  one  which  is  essential 
to  its  enforcement  is  that  clause  which  makes 
it  possible  for  a  city  or  village  to  appropriate 
money  for  water  or  sewage  purification  works 
in  excess  of  the  legal  debt  limit  for  other 
expenditures.  The  plea  of  poverty  cannot, 
therefore,  be  used  as  an  argument  against 
making  the  necessary  improvements  in  sani- 
tary conditions  of  a  community.  In  order  to 
definitely  place  the  responsibility  for  carrying 
out  the  orders  of  the  State  Board  of  Health, 
the  members  of  departments  or  council  of  a- 
municipality,  or  officers  of  a  corporation  are 
made  personally  responsible  for  carrying  out 
orders  of  the  State  Board  of  Health,  and  are 
liable  to  a  personal  fine  for  failure  to  do  so. 
The  Act  above  discussed  has  been  commented 
on  most  favourably  by  sanitary  authorities  in 
the  United  States  as  well  as  abroad.  It  is 
felt  that  this  law  is  just  and  reasonable,  and 
at  the  same  time  can  be  used  to  great  advantage 
in  preventing  the  pollution  of  streams. — 

R.  W.  P. 

Oil  Engines. — Petroleum,  or  oil  engines, 
like  gas  engines,  are  of  the  internal  -  com- 
bustion class  and  resemble  the  latter  in  that 
the  power  is  generated  by  the  explosion,  in  an 
engine  cylinder  operating  on  the  Otto  cycle,  of 
a  compressed  inflammable  gaseous  mixture. 
In  the  oil  engine  this  mixture  is  derived  from 
the  heavier  mineral  oils  of  which  large  supplies 
are  now  available,  principally  from  America 
and  Russia. 

Some   of   the   oils   commonly  used   in   oil 


M.S.E. 


305 


OIL 


ENCYCLOPEDIA   OF 


OIL 


engines  are  Broxbourne  Lighthouse  (flash 
point1  152°  F.),  American  Royal  Daylight 
(flash  point  76°  F.),  and  "  Eussolene  "  (Russian 
ordinary)  of  flash  point  82°  F.  These  oils 
have  an  average  calorific  value  per  pound 
of  ahout  21,000  British  thermal  units,  and  a 
specific  gravity  of  about  '81.  Texas  and 
Roumanian  fuel  oils  are  also  now  being  used 
in  crude  oil  engines. 

PRINCIPLE  OF  THE  OIL  ENGINE. — The  motive 
power  of  the  oil  engine  is  derived  from  the 
explosion,  behind  a  piston  within  a  cylinder, 
of  a  compressed  gaseous  mixture  consisting  of 
oil-vapour  and  air.  The  conditions  are  more 
complex  than  in  the  gas  engine  as  the  liquid 
oil  has  first  to  be  vaporised  within  the  engine 


Inlet  valve 
from  vaporiser. 

~rl 


F 

*-Piston, 

K 

Cylinder 

Exhaust 
valve 

^Clearance  space- 
Mr 
Vaporiser    ~^^-^Oll  spray  nozzle 

FIG.  1. 

before  the  explosions  needed  to  give  the 
periodic  impulses  to  the  piston  can  take  place, 
and,  the  design  of  a  satisfactory  "vaporiser  " 
has  proved  the  most  difficult  portion  of  the 
inventor's  task.  The  main  objects  sought 
have  been  to  satisfactorily  vaporise  the 
cheaper,  heavier,  and  safer  oils  without 
clogging,  and  to  provide  for  the  proper 
admixture  of  air  with  the  oil  vapour.  Three 
of  the  principal  methods  by  which  the 
vaporisation  of  the  oil  is  accomplished  in 
practice  are  shown  diagrammatically  in  Figs. 
1,  2  and  3.  The  arrangement  illustrated  in 
Fig.  1,  is  that  adopted  in  the  Priestman  oil 
engine.  The  jet  of  oil,  controlled  by  the  engine 
governor,  and  a  current  of  air,  is  mixed  in  a 
spraying-nozzle  in  such  a  way  as  to  reduce 
the  oil  to  an  exceedingly  fine  spray  received 

1  "  Flash-point "  =  the  temperature  at  which  oil 
commences  to  give  off  inflammable  vapour  when 
under  atmospheric  pressure.  The  flashing-point 
increases  as  the  density  increases. 


within  a  vaporising  chamber  which  is  heated 
by  a  jacket  through  which  the  engine  exhaust 
fumes  pass.  During  the  outward  or  suction 
stroke,  an  additional  supply  of  air,  also  regu- 
lated by  the  governor,  enters  the  vaporiser 
where  shown  and  forces  the  vaporised  charge 
forward  into  the  clearance  space  of  the  engine 
cylinder.  Upon  the  return  stroke  of  the 
piston,  due  to  the  impetus  of  the  fly-wheel, 
the  inflammable  charge  is  compressed,  becomes 
ignited  by  an  electric  spark  at  the  moment  of 
full  compression,  expands,  doing  work  upon 
the  piston,  and  finally  is  exhausted,  the  return 
stroke  driving  the  products  of  combustion 
through  the  exhaust  valve.  The  Priestman 
engine  gives  an  explosion  every  second 
revolution,  running  on  the  ordinary  Otto 
cycle  common  to  most  gas  and  oil  engines. 
In  this  engine,  the  compression  pressure  of  the 
gaseous  mixture  before  admission  is  greatly 
reduced  as  the  load  reduces,  and  at  very  light 
loads  the  engine  runs  practically  as  a  non- 
compression  engine.  The  fuel  consumption 
per  indicated  horse-power  rises  rapidly  with 
the  reduction  of  compression.  This  is  shown, 
for  example,  in  tests  made  by  Prof.  W.  C. 
Unwin  on  a  9  I.H.P.  engine  working  on 
Russolene  oil,  and  in  which  the  oil  used  per 
I.H.P.  per  hour  was  '816  Ib.  (at  full  load) 
1-063  Ibs.  (at  half-load),  and  5'734  Ibs. 
(running  light),  the  mean  compression  being, 
26,  14'8,  and  6  Ibs.  per  square  inch  respec- 
tively. Another  method  of  vaporising  the  oil 
is  shown  in  Fig.  2.  In  this  there  is  no 
sprayer,  the  oil  being  allowed  to  drop  upon 
a  spiral  or  corrugated  surface  of  heated 
metal.  The  evaporation  is  assisted  by  part 
of  the  air  supply  necessary  for  forming  the 
explosive  mixture  being  drawn  into  the 
vaporiser  over  the  heated  surfaces.  The 
suction  stroke  of  the  piston  draws  the  mixture 
into  the  clearance  space  of  the  cylinder  where, 
by  means  of  the  valve  shown,  it  mixes  with  the 
additional  air  necessary  to  form  an  explosive 
mixture,  and,  upon  the  return  stroke  of  the 
piston  the  charge  is  compressed  and  exploded, 
thus  giving  the  forward  impulse  to  the  piston. 
In  a  modification  of  this  method  sometimes 


306 


OIL 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


OIL 


adopted,  the  air  valve  in  the  cylinder  is  not 
used,  and  the  whole  of  the  air  supply  necessary 
for  the  charge  is  drawn  over  the  vaporising 
surfaces.  Fig.  3  illustrates  the  method  of 
vaporisation  adopted  in  the"Hornsby-Akroyd  " 
oil-engine,  which  is  simple  and  effective.  The 
vaporiser  is  a  bottle -shaped  chamber  or 
extension  of  the  cylinder,  to  which  it  is  con- 
nected by  a  neck  or  contracted  passage.  It  is 


OH  inlet 


Part  of  — 
air  supply 

Spiral 


Valve 


Piston, 
^ 

Cyliftd 

er 

Completion,  of  air  supply 
for  explosive  mixture 


partially  water-jacketed  and,  when  first  start- 
ing the  engine,  is  heated  by  a  lamp ;  after- 
wards, the  combustion  of  the  fuel  within  the 
engine  is  sufficient  to  maintain  the  tempera- 
ture high  enough  to  cause  ignition  of  the 
vapour  and  air  mixture.  The  oil  supply  is 
pumped  from  a  tank  formed  in  the  base  of 
the  engine,  by  means  of  a  small  plunger 
pump,  into  the  hot  vaporiser  during  the  out- 
ward or  air-suction  stroke.  A  little  air  also 
enters  with  the  oil  thus  injected.  Upon 
coming  in  contact  with  the  heated  surfaces 
the  oil  instantly  spreads,  is  vaporised,  and 
mixes  with  the  products  of  combustion  re- 
maining from  the  previous  charge,  but  the 
mixture  does  not  contain  sufficient  oxygen  for 
combustion.  As  the  engine  piston  makes 
its  outward  or  suction  stroke  the  necessary 
additional  air  is  drawn  into  the  clearance 
space  of  the  cylinder  through  a  valve  in 
the  position  shown  but  having  no  connection 
with  the  vaporising  chamber.  At  the  end 
of  the  outward  stroke  of  the  piston  the 
cylinder  is  filled  with  air  whilst  the  vaporiser 
remains  charged  with  the  mixture  of  oil  vapour 
with  some  products  of  combustion.  Upon 
the  return  or  inward  stroke  of  the  piston, 
compression  of  the  cylinder  contents  takes 


place,  and  the  cylinder-air  enters  the  vaporiser, 
thus  supplying  the  necessary  air  for  its  com- 
bustion, until,  at  the  point  of  full  compression, 
ignition  takes  place  and  the  resulting  impulse 
is  given  to  the  piston.  The  time  taken  to 
start  the  engine  is  about  nine  minutes  in 
the  medium  sizes.  The  vaporiser  is  the 
distinguishing  feature  of  this  type  of  engine, 
which  requires  neither  hot  tube,  electric  spark, 
nor  slide  valve  with  flame  for  the  purpose 
of  ignition.  The  Hornsby  cheap  -  fuel  oil 
engine  is  now  made  up  to  500  B.H.P.  The 
present  writer  has  installed  a  80  B.H.P. 
engine  of  this  class  for  waterworks  deep- 
well  pumping  purposes,  and,  in  his  experi- 
ence, the  cost  of  fuel  per  B.H.P.  hour,  using 
Texas  or  Roumanian  oil  at  %\d.  per  gallon, 
was  '2328  of  a  penny.  There  are  many  differ- 
ent makers  of  oil  engines  now  on  the  market, 
amongst  which  may  be  mentioned  the  Black- 
stone,  Britannia,  Campbell,  Crossley,  Cundall, 
Gardner,  Griffin,  Robey,  Ruston-Proctor, 
Samuelson,  and  Tangyes. 

The  "Diesel"  oil  engine,  which  takes  its 
name  from  Herr  Rudolph  Diesel,  has  now 
become  a  motor  of  much  scientific  and  com- 
mercial interest.  It  is  an  internal  combustion 
engine  intended  for  working  with  gaseous 
liquid  or  solid  fuel,  and  is  at  present  developed 


Air  inlet -^ 
Vaporiser 


Oil  spray 
irdet 


b 

Piston 

-  f 

Cylinde 

* 

^naf. 

FIG.  3. 


as  an  oil-engine  working  on  the  four-stroke 
cycle,  and  is  built  vertical.  The  cycle  of 
operations,  though  not  involving  new  prin- 
ciples, is  very  different  from  the  process 
followed  in  the  ordinary  Otto  engine.  The 
leading  distinguishing  features  of  this  engine 
are  : — (1)  The  attainment  within  the  cylinder 
of  the  necessary  temperature  for  ignition  of 
the  charge  by  mechanical  compression  alone 
so  that  no  extraneous  igniting  device  such  as 
incandescent  tube,  or  electric  spark  is  required  • 
307  x  2 


OIL 


ENCYCLOPEDIA  OF 


OPE 


(2)  The  injection  of  the  oil  into  the  cylinder 
only  after  compression  has  been  completed, 
and  only  during  the  first  part  of  the  working- 
stroke  ;  (3)  The  oil  is  injected  gradually  into 
the  highly  heated  air,  each  drop  of  the  spray 
burning  immediately  and  quietly,  so  that  no 
explosion  takes  place. 

EFFICIENCY  AND  TESTING  OF  OIL-ENGINES. — 
The  cost  of  working  oil-engines  varies  accord- 
ing to  the  class  and  cost  of  oil  used,  the 
mechanical  and  thermal  efficiency  of  the 
engine,  and  its  average  working  load.  From 
trials  of  seven  different  makes  of  engines 
running  at  full  load  with  "Bussolene  "  oil 
costing  3frf.  per  gallon,  the  cost  of  one  B.H.P. 
per  hour  was  found  to  range  from  *37rf.  to 
•99d.  The  consumption  of  oil  per  B.H.P. 
showed  an  increase  of  about  32%  when 
at  half-load.  The  total  oil  used  at  full  load 
per  B.H.P.  hour  varied  from  '82  to  1'68  Ibs., 
the  B.H.P.  of  the  engines  ranged  from  about 
5  to  8|  B.H.P.,  and  the  mechanical  efficiency 
from  -7  to  '9. 

THE  TESTING    OF    OIL-ENGINES    is    carried 
out  in  a  very  similar  manner  to  the  testing  of 
gas-engines.     There  is  difficulty  in  obtaining 
satisfactory    indicator     diagrams,     especially 
when  the  engine  is  being  forced  with  excessive 
oil  supply,  so  that  wherever  possible  the  per- 
formance  of    the    engine    should    be    taken 
on   the  B.H.P.  as  in   the   case    of  the   gas- 
engine.     The  weight  of  oil  used  should  be  as- 
certained by  measurement  in  a  carefully  cali- 
brated tank,  and  where  different  classes  of  oil 
are  used  the  calibration  requires  to  be  sepa- 
rately   made   for  each  owing  to  the  varying 
density  of  the  oils.     The  measurement  of  the 
air  supply  for  combustion  must  also  be  made 
in  order  that  the  heat  account  for  the  engine 
may  be  made  up.     This  is  sometimes  taken  on 
the  volume  of  the  delivery  of  the  air-pump 
where  such  is  used,  or  may  be  approximately 
measured  by  an  anemometer  placed  in  a  suit- 
able air  conduit  or  tank.  W.  H.  M. 

Open  Spaces. —  Commons  -  -  Parks  and 
Eecreation  Grounds  and  Gardens  —  Squares, 
Crescents,  and  other  Inclosures  —  Disused 


Churchyards  and  Burial  Grounds — Tree   Plant- 
ing in  Thoroughfares  —  Laying  Out  and  Main- 
taining Grounds— Rights  of  Way  and  Wayside 
Wastes — Statistics. — The  open  space  movement 
owes    its    origin   to    the    continuous    growth 
of   population    during    the   past    40    or    50 
years  in  urban,  as  compared  with  rural  areas, 
and  to  the  consequent  necessity  for  providing 
open  spaces  where  fresh  air,  recreation,  and 
exercise  may  be  obtained  by  the  ever-increas- 
ing number  of  town  dwellers.     The  education 
of  public  opinion  in    regard    to   the   import- 
ance of  this  subject  has  been  largely  due  to 
the  sustained  efforts  of  certain  societies,  viz.  : 
The   Commons   and   Footpaths   Preservation 
Society    (1865),    concerned   chiefly   with   the 
preservation  of  common  lands  now  to  be  found 
generally  in  rural  areas  on  the  outskirts  of 
towns  and  of  rights  of  way ;  the  Kyrle  Society 
(1877),  which  was  formed  for  bringing  beauty 
home  to   the    people;    and    the  Metropolitan 
Public    Gardens    Association     (1882),    which 
takes  steps  to  secure  the  provision  of  parks, 
gardens,  playgrounds,  gymnasia,  the  planting 
of  trees  and  the  placing  of  seats  in  thorough- 
fares,   &c.,  within  or  near  populous  centres. 
These  bodies  have,  inter   alia,  obtained   the 
passing  of  many  Acts  of  Parliament  for  the 
protection  of  commons  and  open  spaces,  and 
for  endowing  public  authorities  with  powers 
of   acquisition    and    management   in    regard 
thereto.     Of  more  recent  date  are  the  London 
Playing  Fields  Society  (1890)  and  the  National 
Trust  for  Places  of  Historic  Interest  or  Natural 
Beauty  (1894),  whose  objects  are  sufficiently 
indicated  by  their    titles.     With    this   intro- 
duction  the    subject   may  be  divided    under 
certain  main  heads  :— 

1.  COMMONS. — Under  the  Commons  Act, 
1876  (39  &  40  Viet.  c.  56),  schemes  can  be 
sanctioned  by  the  Inclosure  Commissioners 
(now  the  Board  of  Agriculture  and  Fisheries) 
embodied  in  a  provisional  order  and  confirmed 
by  Parliament,  for  the  regulation  and  im- 
provement of  commons  for  use  by  the  public, 
with  due  regard  to  the  interests  of  the  lord 
of  the  manor  and  commoners,  conservators 
being  appointed  to  carry  out  schemes  and 


308 


OPE 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


OPE 


exercise  general  powers  of  management.  This 
Act,  although  not  absolutely  prohibiting  the 
inclosure  of  common  lands  (which  under  the 
Inclosure  Acts,  were  being  rapidly  inclosed 
and  divided  up  all  over  the  country),  placed 
a  most  desirable  check  upon  this  policy  by 
declaring  that  future  inclosures  should  not 
be  made,  unless  it  were  proved  to  the  satisfac- 
tion of  the  Commissioners  (now  the  Board  of 
Agriculture  and  Fisheries)  and  of  Parliament 
that  such  inclosures  would  be  of  benefit  to 
the  neighbourhood  generally,  and  not  merely 
to  private  interests.  The  Law  of  Commons 
Amendment  Act,  1893  (56  &  57  Viet.  c.  57), 
contains  a  provision  of  great  importance, 
rendering  it  needful  to  obtain  the  consent 
of  the  Board  of  Agriculture  and  Fisheries 
to  any  inclosure  or  approvement  of  any  part 
of  a  common  purporting  to  be  made  under 
the  Statutes  of  Merton  (20  Hen.  III.  c.  4), 
and  Westminster  the  Second  (13  Edw.  I. 
c.  44).  The  Local  Government  Act,  1894 
(56  &  57  Viet.  c.  73,  ss.  8  and  26),  confers 
powers  relating  to  commons  on  urban,  rural, 
and  parish  councils.  The  Commons  Act,  1899, 
marks  a  further  step  in  advance  by  simplify- 
ing the  procedure  of  the  1876  Act  and  enabling 
the  Board  of  Agriculture  and  Fisheries  itself 
to  give  full  effect  to  a  scheme  of  regulation 
without  the  necessity  for  obtaining  Parlia- 
mentary sanction,  where  no  opposition  to  the 
scheme  is  raised  by  the  lord  of  the  manor. 
It  also  gives  the  widest  interpretation  to  the 
"common"  lands,  which  may  be  regulated 
under  its  provisions.  Commons  within  25 
miles  of  the  City  of  London  boundary  and 
outside  the(  County  of  London  may  be 
acquired  and  managed  by  the  Corporation 
of  London  under  the  Corporation  of  London 
(Open  Spaces)  Act,  1878  (41  &  42  Viet, 
c.  cxxvii.).  Burnham  Beeches,  Coulsdon, 
Riddlesdown,  Kenley,  and  West  Wickham 
Commons  have  thus  been  secured  by  the 
Corporation. 

2.  METROPOLITAN  COMMONS.  —  Under  the 
Metropolitan  Commons  Acts,  1866  to  1898 
(29  &  30  Viet.  c.  122  ;  32  &  33  Viet.  c.  107 ; 
41  &  42  Viet.  c.  71 ;  61  &  62  Viet.  c.  43),  all 


commons  and  commonable  land  wholly  or 
partly  within  the  Metropolitan  Police  District 
(the  Greater  London  of  the  Registrar-General) 
are  specially  exempted  from  inclosure,  whether 
under  the  Inclosure  Acts  or  otherwise,  and 
schemes  can  be  certified  by  the  Board  of 
Agriculture  and  Fisheries,  with  Parliamentary 
sanction,  for  the  improvement,  protection, 
and  management  of  any  such  lands  in  the 
interests  of  the  public,  with  due  regard  to 
private  rights. 

3.  PARKS,  RECREATION    GROUNDS,  GARDENS, 
&c.  —  The    Recreation    Grounds    Act,    1859 
(22  Viet.  c.  27),  enables  land  to  be  conveyed 
to  trustees  for  public  recreation.     The  Public 
Improvement  Act,  1860  (23  &  24  Viet.  c.  30), 
enables  a  two-thirds  majority  of  ratepayers  of 
any  parish  to  secure  land    for    public  walks 
and  playgrounds.     The   Public   Health   Act, 
1875    (38    &    39    Viet.    c.    55,   s.    164),    the 
Public   Health   Acts   Amendment   Act,  1890 
(53  &  54  Viet.  c.  59,  ss.  44  and  45),  and  the 
further  Amendment  Act,  1907  (7  Edw.  VII. 
c.  53,  ss.  76  and  77),  give  urban  authorities 
power  to  acquire  and   manage  public  walks 
and  pleasure  grounds.     These  three  Acts  do 
not  apply  to  London.     The   earlier   Acts  of 
1859  and  1860  and  the  isolated  provisions  in 
the  Public  Health  Acts  must  give  place  in 
importance  to  that  comprehensive  measure, 
the  Open  Spaces  Act,  1906  (6  Edw.  VII.  c.  25), 
embodying  several  previous  Open  Spaces  Acts, 
which  gives  fall  powers  to  local   authorities 
in  England,   Wales,  and   Ireland   (including 
London)  to  acquire  and  maintain  open  spaces 
of  various  kinds  for  public  recreation.    Under 
the  Public  Libraries  Act,  1892  (55  &  56  Viet, 
c.  53,  s.  13),  public  spaces  are  protected  from 
conversion  into  library   building    sites ;    and 
the  London  Government  Act,  1899  (62  &  63 
Viet.  c.  14,  s.  32),  prohibits  borough  councils 
from  alienating  recreation  grounds. 

4.  SQUARES,  CRESCENTS,  OVALS,  AND  SIMILAR 
INCLOSURES. — It  is  very  necessary  to  preserve 
all  such  areas,  whether  or  not  open  to  the 
public,    as    they    form    valuable    oases  and 
breathing   spaces   in   the    midst   of   crowded 
surroundings  and  afford  grateful  relief  to  the 


309 


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ENCYCLOPEDIA   OF 


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eye  of  the  passer-by.  The  Gardens  in  Town 
Protection  Act,  1863  (26  Viet.  c.  13),  provides 
for  the  protection  and  upkeep  of  all  such 
garden  inclosures  and  the  levying  by  the  local 
authority  of  a  special  rate  on  occupiers  entitled 
to  use  them.  The  Open  Spaces  Act,  1906 
(6  Edw.  VII.  c.  25),  contains  special  pro- 
visions and  procedure  for  the  transfer  by 
trustees  and  others  of  such  areas  to  the  local 
authority  with  a  view  to  their  maintenance 
as  public  gardens.  In  London  the  Metro- 
politan Public  Gardens  Association  has  been 
able  to  secure  and  lay  out  many  such  grounds 
and  transfer  them  to  the  appropriate  authority 
to  maintain  for  public  use.  The  London 
Squares  and  Inclosures  (Preservation)  Act, 
1906  (6  Edw.  VII.  c.  clxxxvii.),  marks  the  very 
desirable  commencement  of  making  such 
areas,  of  which  67  are  included  in  its  schedule, 
ineligible  for  building  purposes. 

5.  DISUSED     CHURCHYARDS     AND     BURIAL 
GROUNDS. — Until  the  year  1884  such  areas, 
at  least  in  towns,  were  too  often  allowed  to 
fall  into  a  neglected  and  insanitary  condition, 
or   were   quietly   sold   and   transformed  into 
building  sites.     The  Disused  Burial  Grounds 
Act,  1884  (47  &  48  Viet.  c.  72),  as  amended 
by  the  Open  Spaces  Act,  1887  (50  &  51  Viet. 
c.   32,  s.  4,  and  schedule),  prohibit  building 
thereon.     The  Metropolitan   Public   Gardens 
Association  has  taken  the   lead  in  rescuing 
many  of  these  areas  from  utter  neglect  and 
laying  them  out  as  bright  and  pleasant  public 
gardens.     The  requisite  procedure  is  contained 
in  the  Open  Spaces  Act,  1906  (6  Edw.  VII. 
c.  25).     In  the  Metropolis  the  London  County 
Council  has  special  powers  for  enforcing  the 
observance   of   the   Disused   Burial  Grounds 
Act,  1884,  under  the  Metropolitan  Board  of 
Works  Various  Powers   Act,  1885  (48  &  49 
Viet.  c.  clxvii.). 

6.  TREE    PLANTING    IN    THOROUGHFARES. — 
The   planting   of  trees   in   roads  of  suitable 
width  is  not  only  desirable  from  an  hygienic 
point  of  view,  but  the  foliage  provides  grateful 
shade  and  welcome  relief  to  the  eye  in  the 
midst  of  bricks  and  mortar.     Public  authori- 
ties  outside   London   are  enabled  to   under- 


take this  work  by  the  Public  Health  Acts 
Amendment  Act,  1890  (53  &  54  Viet.  c.  59, 
s.  43),  and  in  London  by  the  London  County 
Council  General  Powers  Act,  1904  (4  Edw.  VII. 
c.  ccxliv..  s.  49).  Great  care  has  to  be  taken  in 
regard  to  planting,  pruning,  watering,  and  main- 
tenance. Irreparable  in  jury  is  too  often  done  by 
entrusting  such  work,  especially  pruning  and 
lopping,  to  unskilful  and  untrained  hands. 
Only  certain  trees  will  flourish  in  the  smoke- 
laden  atmosphere  of  large  towns,  e.g.,  planes 
(par  excellence'),  certain  varieties  of  poplar, 
robinias,  catalpas,  limes,  &c.  The  purer  the 
air,  the  greater  becomes  the  choice.  Care 
has  to  be  taken  to  avoid  gas,  water,  and 
other  pipes.  Soil  in  suitable  and  adequate 
quantities  must  be  imported  where  needful. 
Useful  information  on  this  subject  is  given  by 
the  Metropolitan  Public  Gardens  Association. 

7.  LAYING  OUT  AND  MAINTENANCE  OF  GROUNDS 
FOR  PUBLIC  USE. — It  is  impossible  within  the 
limits  of  an  article  to  give  any  detailed  direc- 
tions.    The  skill  and  knowledge  of  a  trained 
landscape  gardener  is    desirable  in  order  to 
make  the  most  of  a  ground,  with  due  regard 
to   its    size,    use,  and  environment.     In  the 
case  of  commons  and  heaths  the  endeavour 
should  be  to  preserve  all  natural  features  and 
avoid  artificiality  or  elaborate  treatment,  which 
not  only  add  greatly  to  first  cost,  but  involve 
heavy  annual  expense  for  maintenance.     Also 
over   laying-out   tends    to    curtail   the   chief 
function  of  a  ground  as  a  place  to  be  used 
for  exercise  and  recreation  and  not  merely  to 
be  looked  at.    The  public  much  prefer  to  walk 
and  enjoy   themselves   on   grass   and   under 
the   shade    of    trees    than    to    be    shut   out 
therefrom  and  confined  only  to  footpaths  by 
the   introduction  of    unnecessary  flower-beds 
and    shrubberies.     In  really  small   grounds, 
however,  appearance    assumes   more   impor- 
tance, and  greater  elaboration  is  admissible. 

8.  EIGHTS  OF  WAY  AND  EOADSIDE  WASTES. 
— It  is  the  duty  of  district  councils,  whether 
they  be  highway  authorities  or  not,  by  the 
Local  Government  Act,  1894  (56  &  57  Viet, 
c.  73),  to  protect   all  public   rights    of    way, 
to    prevent   obstruction,    whether    within    or 


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MUNICIPAL   AND   SANITAEY  ENGINEEKING. 


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adjacent  to  their  district,  and  to  institute  or 
or  defend  legal  proceedings.  District  councils 
can  be  set  in  motion  by  parish  councils,  and 
in  rural  districts  an  appeal  lies  to  the  county 
council  in  case  of  inaction.  Under  the  same 
Act  it  is  obligatory  upon  district  councils  to 
prevent  unlawful  encroachments  on  roadside 
wastes,  which  add  so  much  to  the  appearance 
of  a  road  and  to  the  pleasure  of  those  using 
it.  As  in  the  case  of  footpaths,  parish  councils 
can  put  district  councils  in  motion  with  an 
appeal  to  the  county  council  in  case  of  neglect. 
County  councils  have  power  to  move  indepen- 
dently in  the  event  of  encroachments  on  main 
roads. 

9.  STATISTICS. — In  1883  in  the  area  of  the 
present   county   of   London   there   were   103 
spaces  of  various  kinds  available  for  public  use, 
about  4,000  acres  in  extent,  which  gave  1  acre 
of  public  space  to  950  people.     At  the  present 
time  (1910)  in  the  same  area  there  are  320 
spaces,  aggregating  over  6,000  acres  in  extent, 
or  1  acre  of  public  space  to  750  people.     In 
1883,  46  selected  cities  and  towns  (excluding 
London)   of  the  United   Kingdom   possessed 
173  public  spaces  over  8,000  acres  in  area, 
equivalent  to   1  acre  of  public  space  to  760 
people.     In  the  same  localities  there  are  now 
(1910)  over  500  public  spaces,  about  14,000 
acres  in  area,   or  1   acre  of  public  space  to 
640  people. 

10.  CONCLUSION. — Great  strides  have   been 
made  during    the   last   25    years   in    regard 
to    the    provision    of    open    spaces.      Public 
authorities  no   longer  look  askance  as  they 
once  did  at  proposals  brought  to  their  notice 
by  open  space  societies  or  private  individuals. 
But  the  continued  existence   of   societies  is 
none  the  less  necessary  in  order  to  be  on  the 
watch  to  take  advantage  of  favourable  oppor- 
tunities, to  harmonise  conflicting  interests,  to 
initiate  and  put  schemes  into  workable  shape, 
and,  it  may  be,  to  find  part  of  the  money  from 
voluntary    sources    before   bringing   them    to 
the  notice  of  one  or  more  public  bodies  con- 
cerned.    It  has  begun  to   be  perceived  that 
open  spaces  are  just  as  needful  for  the  health 
and  welfare  of    the   community  as   roads  or 


drainage  schemes.  Prevention  is  better  than 
cure,  and  fresh  air  and  open  spaces  are  better 
than  hospitals.  So  far  the  movement  has  not 
been  systematised,  but  has  proceeded  hap- 
hazard, and  too  often  the  slums  of  the  older 
part  of  a  town  are  repeated  in  the  newly-built 
suburb  through  lack  of  forethought.  It  is 
therefore  very  needful,  especially  in  new  locali- 
ties where  building  proceeds  apace,  for  the 
local  authorities  to  take  time  by  the  forelock 
and  secure  open  spaces  ere  too  late.  Under 
the  Housing,  Town  Planning,  &c.,  Act,  1909, 
the  need  of  systematic  provision  is  to  some 
extent  recognised,  as  no  town  planning 
scheme  will  be  complete  which  does  not 
provide  for  an  adequate  supply  of  open 
spaces.  B.  H. 

Otto  Cycle. — (See -"GAS  ENGINES"  and 
"  OIL  ENGINES.") 

Outfall  Sewers.— (See  "SEWERAGE.") 

Oxidation  of  Sewage  is  effected  naturally 
by  atmospheric  oxygen,  or  artificially  by 
oxidising  chemicals. 

NATURAL  OXIDATION. — In  this  case  the  gas 
must  first  dissolve  in  the  liquid  and  then 
must  be  aided  by  bacteria,  as  in  sterilised 
sewage  there  is  little  or  no  action.  For 
the  conversion  of  the  carbon  and  nitro- 
gen of  the  organic  substances  into  carbonic 
acid  and  nitrites  or  nitrates  a  large  quan- 
tity of  oxygen  is  required ;  thus  to  nitrify- 
in  a  sewage  five  parts  of  N  per  100,000  will 
demand  about  half  its  volume  of  air,  or  about 
15  volumes  of  fully  aerated  water  (7  c.c.  0  per 
litre)  (see  "  NITRIFICATION").  The  absorption  of 
a  gas  by  a  liquid  is  hindered  by  the  layer  of 
vapour  of  the  liquid  which  is  constantly  form- 
ing on  the  surface.  This  layer  is  not  affected 
by  currents  in  the  liquid  as  long  as  the  surface 
is  tranquil,  and  is  only  penetrated  by  gaseous 
diffusion.  Therefore,  calm  and  deep  water 
when  deprived  of  oxygen  by  bacterial  changes 
is  only  slowly  re-aerated  by  the  atmosphere. 
The  absorption  is  quickened  by  winds,  and  by 
fountains,  cascades  and  weirs,  but  Fowler 


311 


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ozo 


found  at  Manchester  that  "  even  when  air  is 
forced  through  the  liquid  for  some  days  the 
improvement  was  less  than  that  effected  by 
bacterial  niters  in  eight  hours."  Several 
processes  of  sewage  treatment  have  included 
forced  aeration,  but  the  results  do  not  justify 
the  expense,  and  a  free  natural  ventilation  of 
filters  is  sufficient.  Green  algae  give  off  oxygen 
in  light  and  so  favour  oxidation  in  waters. 
One  of  the  chief  tests  of  a  sewage  or  effluent 
is  the  amount  and  the  rate  of  its  consump- 
tion of  oxygen  (which  is  only  approximately 
judged  by  its  permanganate  consumption),  and 
the  Royal  Commission  on  Sewage  have  pro- 
visionally laid  down  that  after  filtration 
through  filter  paper,  when  it  must  not  show 
more  than  8%  of  suspended  solids,  it 
should  not  absorb  more  oxygen,  dissolved 
or  atmospheric,  than,  in  parts  by  weight  per 
100,000,  0-5  in  24  hours,  1-0  in  48  hours,  or 
]'5  in  five  days.  The  Commissioners  pro- 
pose for  the  determination  an  apparatus 
devised  by  Dr.  Adeney,  but  a  simpler 
method  preferred  by  the  writer  and  others 
is  to  completely  fill  a  number  of  250  c.c. 
stoppered  bottles  with  the  sewage  (diluted  if 
necessary)  or  effluent,  previously  saturated  by 
shaking  with  air,  and  to  determine  the  dis- 
solved oxygen  by  a  rapid  process,  such  as 
Eideal  and  Stewart's  modification  of  Winkler's, 
Analyst,  1901,  p.  141,  successively  in  the 
samples  at  12,  24,  48  hours,  or  longer,  at  the 
same  time  noticing  the  odour. 

ARTIFICIAL  OXIDATION. — For  this  purpose 
chlorine  and  ozone  are  the  only  practicable 
agents.  Manganese  compounds  .  have  been 
tried,  but  are  precluded  by  expense  and  for 
other  reasons,  and  a  similar  remark  applies 
to  peroxide  of  chlorine  (Berge).  (See  "  NITRIFI- 
CATION," "  CONDY'S  FLUID,"  "  CHLORIDE  OF 
LIME,"  "ELECTROLYSIS,"  and  "  OZONE.") 

S.  E. 

"  Oxidium." — An  indestructible  highly 
porous  mineral  substance  used  as  a  filtering 
material  between  layers  of  silica  in  the  Candy 
Compressed  Air  and  Oxidising  Waterworks 
Filters.  It  possesses  properties  somewhat 


similar  to  those  of  spongy  platinum,  and  is  of 
volcanic  origin.  It  is  treated  by  a  special 
patent  process  in  order  to  impart  to  it  the 
peculiar  property  of  rendering  more  powerful 
the  oxygen  contained  in  the  air  with  which 
the  water  in  the  filter  is  first  saturated.  The 
atmospheric  oxygen  is  occluded  upon  the 
microscopical  and  interstitial  spaces  of  the 
"  oxidium,"  and  is  utilised  for  the  instan- 
taneous oxidation  of  the  iron  contained  in 
solution  in  the  water  treated  by  these 
mechanical  filters.  The  "  oxidium  "  is  hard 
and  quite  insoluble,  and  simply  acts  in  con- 
junction with  the  oxygen  in  the  air  within  the 
filter. 

Oxychloride  is  a  chemical  preparation 
produced  electrotytically  by  a  company  named 
Oxychlorides,  Ltd.,  and  used  for  the  deodori- 
sation  of  septic  tank  liquors,  &c.,  as,  for 
example,  in  cases  where  the  sewage  is  more 
offensive  than  usual  through  the  presence  of 
brewery  refuse  or  other  wastes.  It  has  been 
used  at  Stone  in  Staffordshire,  and  Guildford. 

Oxynite. — A  precipitant  for  purifying 
sewage  introduced  by  the  Oxygen  Sewage 
Purification  Co.,  Ltd.,  which  has  for  its  active 
principle  compounds  of  manganese. 

Ozone  in  Air. — Ordinary  oxygen  exists  as 
the  molecule  Oa,  but  by  electric,  preferably 
silent,  discharges,  or  in  some  slow  oxidations, 
a  portion  of  it  is  condensed  to  the  molecule 
OaJ  the  extra  atom  of  0  is  called  its  "  active 
oxygen,"  since  it  rapidly  oxidises  and  is 
removed  by  sulphuretted  hydrogen,  sulphur- 
ous acid,  most  metals,  and  organic  substances. 
Certain  tests  point  to  ozone  in  minute  quantity 
as  a  normal  constituent  of  the  atmosphere ; 
more  in  sea  air  than  inland,  at  high  than  at 
low  levels,  and  little  or  none  in  towns  ;  more 
after  thunderstorms,  and  least  in  damp  and 
foggy  weather ;  more  in  summer  than  in 
winter,  at  night  than  in  daytime,  and  most  at 
dawn.  It  is  looked  for  by  suspending  papers 
(protected  from  dust,  rain  and  direct  sunlight) 


312 


ozo 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


OZO 


moistened  with  various  solutions.  The  follow- 
ing is  a  table  of  reagents  in  use  and  of  the 
effects  on  them  of  other  possible  constituents 
of  air. 


B 

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1  Blued  at  once  by  Tj^^V^^  by  weight  of  ozone,  and 
slightly   by   0'0002  to  0'0003  mgm.    (See    Eeport  on 
Ventilation  of  House  of  Commons,  1906,  p.  100  ;  it 
was  concluded  that   peroxide   of   hydrogen,  and  not 
ozone  was  present.)   Paper  dipped  in  phenolphthalein 
and  KI  is  reddened  by  ozone  and  browned  or  blued  by 
Cl  or  nitrous. 

2  It  is  said  that  browning  due  to  ammonia  is  distin- 
guished by  not  being  immediately  blued  by  guaiacum. 


Approximate  meteorological  measurements 
("  ozonometry ")  are  made  by  comparison 
with  standard  tints  produced  by  known 
quantities  of  ozone.  Its  actual  amount  may 
be  determined  by  aspirating  a  large  measured 
volume  of  air  through  a  wash- bottle  containing 
permanganate,  then  through  caustic  soda,  and 
finally  into  a  solution  of  pure  KI,  and  titrating 
the  liberated  iodine  with  thiosulphate.  Houzeau 
judged  the  maximum  proportion  at  ordinary 
levels  to  be  one  volume  in  several  hundred 
thousand  of  air.  (See  "  AIR,  ATMOSPHERIC, 


PURITY  OF.") 


S.  R. 


Ozone  (Purification  of  Water  by).— 

Ozone  is  the  ideal  agent  for  purifying,  since  it 
leaves  behind  it  only  ordinary  oxygen,  and 
nothing  foreign  to  the  water.  It  was  first 
tried  for  this  purpose  by  Frohlich,  and 
Ohlmuller  proved  that  it  energetically  attacked 
bacteria  in  water  from  which  any  excess  of 
inert  organic  matter  had  Jbeen  previously 
removed.  These  experiments  followed  the 
construction  of  large  industrial  ozonisers  by 
Siemens  &  Halske  at  Berlin,  which  firm  in 
1898  erected  an  experimental  plant  at  Martini- 
kenfelde,  and  afterwards  larger  installations 
for  the  towns  of  Wiesbaden  and  Paderborn.  Air 
ozonised  to  2^  to  3  grammes  per  cubic  metre 
passed  upwards  through  a  tower  filled  with 
flints,  and  met  a  descending  current  of  roughly 
filtered  water.  The  cost  was  about  2frf.  per 
1,000  gallons  of  water  treated,  and  a  very 
impure  water  was  sterilised  down  to  2  to  9 
organisms  per  c.c.  Earlier,  in  1898,  Tindal 
started  his  apparatus  at  Oudshoorn,  Holland, 
and  in  1895  worked  it  experimentally  at 
Paris,  also  at  Brussels  and  Ostend,  and  it  was 
adopted  for  limited  supplies  at  several  other 
places.  Leon  Gerard  estimated  the  cost  at 
0'45d.  per  1,000  gallons.  The  bacterial 
reports  of  Van  Ermengem,  Marmier,  and 
Roux  were  satisfactory.  Tindal's  apparatus 
attained  intimate  admixture  and  duration 
of  contact  by  passing  the  water  and  ozonised 
air,  either  in  the  same  or  an  opposite  direc- 
tion, through  towers  divided  by  perforated 


313 


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ENCYCLOPEDIA   OF 


PAI 


diaphragms  "  or  other  equivalent  dispositions  " ; 
another  form  had  pulverisers  or  spray  jets ; 
and  the  partially  exhausted  air  at  the  exit 
could  be  dried,  re-ozonised,  and  returned. 
Subsequently,  in  1897,  appeared  the  Marmier- 
Abraham1  and  Otto  patents.  The  former  had 
a  mixing  tower  filled  with  flints  or  bricks  ;  the 
latter  injected  the  water  and  ozonised  air 
together  by  means  of  a  pulveriser,  called  an 
"  emulsor,"  and  later  (1905)  added  a  column 
of  flints  through  which  a  second  current  of 
ozonised  air  was  ascending.  These  patents 
are  now  amalgamated,  and  are  at  work  on  the 
town  supplies  of  Nice  and  Chartres,  and 
(experimentally)  at  St.  Maur,  Paris.  Tindal's 
previous  patent  after  his  death  was  acquired 
by  De  Frise,  who  has  improved  the  apparatus 
and  process,  and  has  introduced  into  his  plant 
an  ozoniser  similar  to  the  Siemens,  and  an 
ozone-recuperating  circuit.  An  installation  on 
this  principle  at  the  Paris  Municipal  Water- 
works, St.  Maur,  applied  to  treating  sand- 
filtered  Marne  water,  which  is  coloured  and 
bacterially  impure,  was  examined  by  Eideal  in 
September  and  October,  1908.  He  found  that 
the  sterilisation  was  effective  and  the  de- 
colorisation  complete  without  other  change, 
that  the  working  was  successful,  and  that  the 
De  Frise  process  is  a  satisfactory  method  of 
ensuring  a  standard  of  purification  for  a  muni- 
cipal water  supply.  Miquel's  examination  in 
March  and  April,  1908,  had  led  to  a  similar 
conclusion.  The  total  cost  of  the  process 
would  be  about  0'33d.  per  1,000  gallons  of 
water  treated,  and  the  actual  amount  of  ozone 
added  at  St.  Maur  was  equal  to  0'542  gramme 
of  active  oxygen  per  cubic  metre  (parts  per 
million).  This  is  chemically  equivalent  to 
2'4  parts  per  million  of  available  chlorine, 
which  was  the  figure  found  for  tertiary 
effluent  at  Guildford.  (See  "  CHLORINE 
PURIFICATION"  and  "ELECTRICITY.") 

S.  E. 

Pail  System.— (See  "PRIVIES.") 

1  Tried  at  Lille,  1898,  later  at  Schiedam,  and  at 
Moscow  in  1901.  See  also  Electrochem.  Ind.,  February, 
1903,  and  Eclair  age  Electrique,  December  12, 1903. 


Paint-Spraying  Machines.— When  these 
appliances  were  first  brought  out  they  were 
much  ridiculed  on  the  ground  that  it  was 
impossible  to  apply  paint  serviceably  except 
by  means  of  the  brush  ;  but  it  has  been  shown 
that  this  is  quite  a  mistake,  and  in  certain 
cases, notably  when  the  surface  is  rough,  a  great 
deal  of  saving  may  be  effected  by  the  use  of  a 
good  paint-spraying  machine.  If  a  perfectly 
smooth  and  highly  finished  surface  was 
required,  such,  for  example,  as  a  front  door  of 
a  private  residence,  a  paint-spraying  machine 
would  be  useless,  but  for  bridge  work,  lime- 
washing,  rough  brickwork,  such  as  railway 
arches  used  for  storage,  &c.,  and  in  many  other 
cases,  the  paint- spraying  machine  possesses 
many  advantages  over  the  old-fashioned  plan. 
It  will  be  understood  that  the  paint  or  lime- 
wash  is  forced  by  means  of  compressed  air  from 
the  nozzle  of  the  apparatus  into  a  fine  spray, 
which  becomes  more  diffused  the  further 
away  the  nozzle  is  held  from  the  surface,  but 
the  inequalities  and  holes  are  all  well  covered 
in  a  short  time,  and  in  a  manner  which  would 
be  impossible  if  a  brush  were  used.  Paint- 
spraying  machines  are  now  made  with  two 
nozzles  side  by  side,  and  by  means  of  their  use 
a  surface  may  be  painted  or  whitewashed  in  a 
remarkably  short  space  of  time.  A.  S.  J. 

Paints  and  painting. — General  Survey- 
Washable  Distempers — Painting  Iron — Removing 
Paint. — The  municipal  engineer  usually  con- 
siders paint  chiefly  from  the  point  of  view  of 
its  protective  qualities  against  decay,  and  not 
for  its  decorative  value.  The  base  of  most 
paints  used  for  white  work  is  white  lead,  but 
on  iron  work  other  pigments  are  generally 
preferred.  The  preference  for  white  lead  is 
based  upon  the  fact  that  this  pigment,  when 
ground  in  linseed  oil,  possesses  the  quality 
known  by  painters  as  "  body,"  which  means 
the  property  of  hiding,  or  masking,  the  surface 
to  which  it  is  applied.  This,  however,  has 
really  nothing  to  do  with  the  actual  durability 
of  the  paint,  because  one  which  has  little  or 
no  body  might  resist  the  destroying  action  of 
atmospheric  conditions,  water,  chemicals,  &c., 


314 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


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much  longer  than  the  white  lead.  Still,  the 
object  in  painting  is  as  a  rule  to  obscure 
the  surface,  to  hide  the  knots  in  the  grain  of 
wood,  and  the  paint  which  has  the  most  body 
effects  this  object  in  fewer  coats  than  the  one 
which  has  less  body.  For  purely  protective 
purposes  it  is  now  generally  recognised  that 
an  admixture  of  pigments  produces  the  best 
results,  and  that,  while  there  is  no  ideal  pig- 
ment, or  one  which  possesses  the  whole  of  the 
virtues,  yet,  where  one  falls  short  of  perfection, 
the  deficiencies  may  be  made  up  by  adding 
the  proper  proportion  of  another.  Generally 
speaking  paint  may  be  said  to  be  composed  of 
either  white  lead,  zinc  oxide,  or  other  white 
pigments,  mixed  wTith  the  necessary  colour 
pigments  to  produce  the  desired  shade,  tint, 
or  hue,  or  of  certain  natural  earth  colours, 
such  as  ochre,  sienna,  oxide  of  iron,  &c.  In 
most  cases  these  pigments  are  produced  in  the 
form  of  a  dry  powder,  which  is  ground  in  a 
vehicle,  almost  invariably  linseed  oil.  The 
durability  of  such  paint  depends  principally 
upon,  first,  the  quality  of  the  linseed  oil,  that 
is  to  say,  whether  it  is  pure  and  of  the  best 
grade,  secondly,  upon  the  degree  of  fineness 
to  which  the  pigment  is  ground,  and,  thirdly, 
a  thorough  admixture  of  the  whole.  The  fine- 
ness of  pigments  is  a  point  to  which  much 
attention  has  been  drawn  in  recent  years,  but 
it  is  well  recognised  that  within  reasonable 
limits  the  finer  ground  the  pigment  is,  the 
better  paint  it  makes.  The  question  of  purity 
may  almost  be  considered  as  a  side  issue  ; 
taking  white  lead  as  an  example,  there  can  be 
no  doubt  that  exceedingly  finely-ground  white 
lead  mixed  with  25  %  of  barytes  will  probably 
be  very  much  more  durable  than  a  pure  and 
coarsely-ground  white  lead.  Painters,  as  a 
rule,  purchase  their  white  lead  or  other  pig- 
ments in  the  form  of  a  stiff  paste,  and  they 
then  thin  it  for  application  by  means  of  a 
brush  by  adding  a  sufficient  quantity  of  linseed 
oil,  either  raw  or  boiled,  and  American 
turpentine.  The  proportion  of  these  "  thin- 
ners,"  as  they  are  technically  called,  depends 
upon  the  condition  of  the  surface  to  which  the 
paint  is  to  be  applied.  If  it  is  absorbent, 


such  as  plaster  or  open-grained  wood,  much 
more  oil  and  turpentine  will  be  required  than 
is  the  case  with  iron,  which  is  looked  upon  as 
practically  non-absorbent,  or  at  least  after  the 
first  coat.  Driers  are  used  to  facilitate  the 
absorption  of  oxygen  from  the  atmosphere, 
and  this  quickly  affects  the  drying  or  hardening 
of  the  coat  of  paint.  The  proportion  of  driers 
used  varies  largely  with  the  kind  of  pigment. 
Vandyke  brown  and  the  blacks  require  a  very 
large  proportion  of  driers,  while  red  lead  is 
in  itself  a  dryer  and  requires  no  addition. 
White  lead  is  also,  to  some  extent,  a  dryer,  and 
very  little  additional  driers  should  be  em- 
ployed. The  quantity  of  turpentine  is, 
perhaps,  not  so  important  as  the  other  con- 
stituents of  the  paint,  because  all,  or  at  least 
the  greater  part  of  it  evaporates  when  the 
paint  dries.  Still,  too  much  turpentine  would 
render  the  paint  too  thin  for  practical  purposes. 
Only  recently,  American  turpentine  was  looked 
upon  as  a  sine  qua  non  in  all  good  paint, 
but  the  continued  high  price  of  the  product 
has  caused  the  paint  manufacturer  to  look  very 
closely  into  the  question,  and  what  is  known 
as  "  white  spirit "  in  its  various  forms, 
frequently  mixed  with  a  proportion  of 
American  turpentine,  is  now  successfully  used 
as  a  substitute.  White  spirit,  it  may  be 
remarked  in  passing,  is  petroleum  distilled 
in  such  a  manner  that  it  has  no  oily  residue, 
while,  at  the  same  time,  it  does  not  evaporate 
so  rapidly  as  to  interfere  with  the  manual 
application.  In  many  cases  the  municipal 
engineer  will  desire  to  use  paint  which  is 
simply  preservative,  quite  irrespective  of  its 
"  body,"  or  covering,  and  in  such  a  case  pro- 
bably a  mixture  of  white  lead  and  barytes  in 
equal  proportions  will  be  as  effective  as  any- 
thing. Zinc  oxide  may  also  be  employed 
for  the  same  purpose,  but  the  price  is  slightly 
higher  than  white  lead,  although  lower  in 
reality,  because  it  spreads  over  or  covers,  when 
made  up  into  paint,  at  least  25%  greater 
surface.  Red  lead  possesses  advantages  when 
hard  wear  and  tear  has  to  be  resisted,  as,  for 
example,  in  painting  barrows,  carts,  &c.  (See 
"  RED  LEAD.")  The  protection  of  ironwork  is 


315 


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PAI 


obviously  of  great  importance,  and  there  are     mical  paint  can  be  obtained,  always  provided 


various  special  paints  made  for  this  purpose. 
Some  engineers  consider  oxide  of  iron  the  best 
protective  paint  for  iron,  while  others  are  just 
as  strongly  in  favour  of  red  lead.  The  Tower 
Bridge  was  repainted  from  end  to  end  with 
white  lead  only,  although  this  is  contrary  to 
the  usual  practice.  There  is  at  this  time  a 
strong  tendency  towards  the  use  of  graphite 
paints,  i.e.,  those  made  from  plumbago  ground 
in  oil.  The  pigment  used  for  this  purpose 
is  often  mixed  with  silica  and  various  other 
materials.  Graphite  paint  is  very  exten- 
sively used  in  the  United  States  of  America, 
and  other  places,  and  it  appears  to  be  certain 
to  succeed  equally  well  here  when  its  merits 
become  more  widely  known.  In  a  table 
drawn  up  by  Mr.  J.  Cruikshank  Smith  which 
gives  the  comparative  durability  of  various 
paints,  it  is  clearly  shown  that  graphite 
paints  are  superior  to  all  others  when  the 
following  points  are  taken  into  consideration : 
— First,  the  prime  cost ;  second,  the  average 
time  the  paint  will  last,  i.e.,  the  period  before 
repainting  will  be  necessary  ;  third,  the 
spreading  capacity — that  is  the  surface  a 
given  quantity  will  cover  when  made  into 
paint  ;  and  fourth,  the  cost  of  application. 
It  cannot  be  too  strongly  urged  that  the  actual 
cost  of  labour  in  applying  a  paint  is  a  very 
material  item  in  determining  its  economic 
value.  Some  authorities  place  the  cost  of 
application  at  two-thirds,  but,  even  taking  it 
at  one-half  the  cost  of  the  paint,  it  will  be  seen 
that  it  is  by  no  means  economical  to  use  a 
paint  which  requires  to  be  frequently  renewed. 
Of  late  years  the  subject  of  painting  has  been 
dealt  with  on  a  scientific  basis,  and  the  old 
idea  that  the  best  paint  for  all  purposes  is 
necessarily  a  mixture  of  white  lead,  linseed 
oil,  and  turpentine  has  been  shown  to  be 
erroneous,  and  engineers  are  recognising  the 
fact  that  a  paint  which  would  be  very  suitable 
and  cheap  for  one  purpose  might  be  wholly 
unsuitable  for  another.  It  is  also  becoming 
recognised  that  an  admixture  of  pigments, 
which  has  already  been  referred  to,  is  a  plan 
by  means  of  which  the  best  and  most  econo- 


that  the  thinners  are  of  the  proper  kind  and 
are  used  in  the  right  proportions.  There  is 
also  a  tendency  towards  a  departure  in  another 
direction,  viz.,  that  of  varying  the  con- 
stituencies of  the  several  coats  of  paint.  A 
manufacturer  may  bring  out  a  special  paint 
produced  by  a  careful  study  of  the  require- 
ments of  ordinary  work,  and  probably  also  as 
a  result  of  an  elaborate  set  of  experiments, 
but  he  is  under  the  disadvantage  that  the  paint 
must  necessarily  be  uniform  in  quality.  The 
painter,  on  the  other  hand,  can  mix  each  coat 
of  paint  for  the  purpose  of  which  it  is  to  be 
applied.  The  painter  also  varies  the  quantity 
of  thinners  in  several  coats  of  paint  in  such  a 
manner  that  one  coat  is  rather  oily  and  the 
next  rather  "  flat."  This  has  the  effect  of 
giving  a  grip,  or  hold,  of  one  coat  upon  the 
other  and  is  productive  of  good  results.  In 
ordinary  painting  the  only  difference  between 
the  several  coats  of  paint  is  in  the  priming 
coat,  which  is  usually  mixed  with  a  small  pro- 
portion of  red  lead,  in  order  to  give  rigidity 
and  firmness  to  the  foundation.  With  the 
exception  of  the  proportion  of  thinners  already 
referred  to,  the  composition  of  the  subsequent 
coats  is  almost  identical.  The  very  extensive 
use  of  enamels  in  recent  years  has  led  to 
further  investigation  which  shows  clearly  that 
not  only  should  the  thinners  be  varied  in 
different  coats,  but  the  pigments  should  be 
likewise  changed.  An  example  may  be  given 
in  the  preparation  of  ordinary  work  which  has 
to  be  finished  in  white  enamel.  In  this  case 
the  primary  coat  should  be  white  lead  with  a 
little  liquid  dryer  of  good  quality  ;  red  lead 
should  be  omitted  here  in  case  it  finds  its  way 
through  the  subsequent  coat.  The  second  coat 
should  be  also  of  white  lead  mixed  to  an  oily 
finish,  and  the  third  coat  should  be  of  paint 
made  of  white  lead  and  zinc  oxide  in  the  pro- 
portions of  one-half  of  each.  The  fourth  coat 
should  be  pure  zinc  oxide  mixed  quite  flat,  i.e., 
mixed  with  turpentine  only,  without  oil,  but 
with  a  little  binder,  such  as  gold  size.  These 
four  coats  should  be  rubbed  down  perfectly 
level,  when  a  white  and  flat  surface  will  be 


316 


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MUNICIPAL   AND    SANITAEY   ENGINEERING. 


PAI 


obtained,  which  will  give  a  splendid  surface 
for  the  white  enamel  to  be  afterwards  applied, 
and  this  will  show  up  to  the  best  advantage. 
The  object  of  using  zinc  oxide  for  the  final 
coat  is  that  it  is  very  white,  much  whiter  than 
white  lead,  which  is  comparatively  of  a  yellow- 
ish cast.  The  final  coat  of  white  enamel  is, 
to  some  extent,  transparent,  so  that  if  an 
undercoat  of  white  is  given  it  will  show  through 
and  give  the  best  results. 

WASHABLE  DISTEMPER  is  a  modern  class  of 
water  paint  largely  used  and  of  great  hygienic 
value.  This  class  of  paint  is  supplied  in  three 
forms,  in  the  form  of  dry  powder,  in  a  stiff 
paste,  and  in  a  condition  ready  for  use. 
Washable  distempers  are  made  in  a  very  large 
number  of  useful  colours  and  are  easy  of 
application.  They  produce  a  perfectly  flat 
finish  free  from  gloss.  There  are  not 
many  brands  which  are  really  washable, 
but  the  best  of  them,  a  month  or  so  after 
application,  may  be  washed  down  with  a  fine 
sponge  without  injury.  For  this  reason 
washable  distempers  are  eminently  suitable 
for  the  walls  of  churches,  hospitals,  infirm- 
aries, and  public  institutions  generally.  Those 
parts  which  are  subject  to  much  wear  may 
be  protected  by  giving  the  distemper  a 
coat  of  varnish.  In  most  cases  it  will  be 
necessary  to  size  the  distemper  before  the 
varnish  is  applied,  and  unless  this  is  done  the 
colours  of  the  distemper  will  be  much  darkened 
by  the  varnish.  On  occasions  this  may  be  an 
actual  advantage,  as  in  the  case  of  a  room 
decorated  throughout  with  a  distemper,  say,  in 
a  series  of  greens.  Very  light  green  could  be 
used  on  the  ceiling,  the  walls  could  be  a 
medium  shade  of  the  same  green,  and  then 
a  dado,  5  ft.  or  more  high,  could  be  formed 
with  a  suitable  border  on  top.  By  varnishing 
this  dado  the  distemper  will  be  darkened,  and 
the  decorative  effect,  on  the  whole,  will  be 
good.  In  many  cases  engineers  prefer  to  use 
enamel  instead  of  distemper  for  the  walls  of 
hospitals,  on  the  plea  that  the  surface  should 
be  frequently  washed  down,  so  as  to  remove 
any  possible  germs  or  bacteria.  It  is  hardly 
necessary  now  to  enter  into  the  different 


aspects  of  this  controversy,  but  it  will  be  suffi- 
cient to  say  that  if  the  funds  admit  of  a  con- 
stant washing  down  of  the  walls  and  of  the 
original  cost  of  the  enamel,  that  material  is 
the  best  for  the  walls  of  public  institutions. 
But  if,  as  usually  happens,  the  walls  are  not 
actually  washed  down,  except  twice  a  year, 
then  washable  distemper,  which  costs  so  much 
less,  answers  the  purpose  equally  well. 

PAINTING  IRON. — The  first  essential  in  paint- 
ing ironwork  is  to  remove  every  particle  of 
rust,  as,  unless  this  is  done  very  thoroughly 
indeed,  the  rust  will  continue  to  spread  under- 
neath the  surface  of  the  paint.  The  means 
adopted  for  removing  the  rust  are  usually 
chipping  off  with  a  chisel,  and  thoroughly 
brushing  with  stiff  wire  brushes  ;  but  the  job 
is  a  long  and  expensive  one,  and  the  writer 
suggests  that  there  is  room  for  the  introduc- 
tion of  a  little  instrument  of  hammerlike 
character,  actuated  by  electric  power,  which 
could  be  also  used  for  scraping.  When 
it  is  practicable,  it  is  unquestionably  cheapest 
in  the  end  to  thoroughly  clean  the  iron 
by  means  of  a  sand  blast.  This  process 
yields  a  surface  like  silver,  and,  although  it  is 
expensive  at  the  start,  yet  the  paint — if  a  good 
one — will,  upon  such  a  surface,  last  for  years, 
whilst  if  it  is  applied  over  rust,  scale,  &c.,  its 
life  is  a  very  brief  one. 

REMOVING  PAINT. — The  old-fashioned  plan 
of  removing  paint  is  to  burn  it  off  by  means 
of  a  blow-lamp  and  scraper.  There  is  objec- 
tion, however,  to  the  fumes  thus  given  off, 
particularly  when  the  work  is  indoors,  and 
also  to  the  liability  to  burn  delicate  mouldings, 
&c.,  if  great  care  is  not  taken.  There  are  a 
number  of  "  paint  removers  "  on  the  market, 
the  best  of  which  are  free  from  caustic  soda, 
and  consist  of  a  substance  which  does  not 
injure  the  hands,  but  which,  when  brushed  on 
paint,  softens  it  so  thoroughly  that,  after  a 
period  of  a  few  minutes  to  a  quarter  of  an 
hour,  it  may  be  easily  wiped  off  with  a  piece 
of  waste.  Caustic  paint  removers  require  the 
application  of  an  acid,  such  as  vinegar,  to  kill 
any  of  the  soda  which  may  be  left,  but  with 
the  new  improved  paint  removers  it  is  not 


317 


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PIP 


necessary,  and  all  that  is  required  is,  after 
the  paint  is  taken  off,  to  wipe  over  the  surface 
with  a  piece  of  rag  moistened  with  benzine  or 
turpentine  and  the  work  is  then  ready  for 
immediate  painting.  A.  S.  J. 


Parks    and    Pleasure 

"OPEN  SPACES.") 


Grounds. — (See 


Paving. — (See  "  ROADS  AND  STREETS.") 

Penstock. — A  penstock  is  an  appliance  fitted 
to  the  mouth  or  entrance  of  a  pipe  or  conduit, 
as  in  main  drainage  works,  for  the  purpose  of 
controlling  the  flow  of  liquid  through  such 
pipe.  The  words  "  penstock  "  and  "  valve  " 
are  used  somewhat  loosely  in  the  same  con- 
nection, but  the  term  "penstock"  is  more 
generally  applied  when  dealing  with  pipes 
and  conduits  of  large  diameter.  Numerous 
varieties  of  penstocks  will  be  found  in  the 
makers'  catalogues.  A  typical  form  of  such 
appliance,  suitable  for  an  egg-shaped  sewer, 
is  provided  with  counter-balance  weights  and 
a  rack  and  worm  arrangement  to  facilitate 
opening  and  closing.  To  avoid  corrosion,  to 
give  a  more  perfect  and  watertight  fit,  and  to 
produce  ease  of  working,  penstocks  are  fre- 
quently fitted  with  gun-metal  working  faces 
and  worm,  and  all  bearings  bushed  with  gun- 
metal. 


Percolating  Beds. — (See 

POSAL.") 


SEWAGE  Dis- 


Pipe  Joints,  Stoneware.  —  The  joint 
commonly  made  use  of  for  stoneware  pipes 
is  the  ordinary  spigot  and  socket  joint,  which 
in  most  cases  answers  admirably  if  well  made 
with  neat  cement.  Care  must  be  taken  that 
the  pipes  when  joined  are  concentric  and  that 
the  whole  of  the  socket  is  well  filled,  leaving 
no  interstices  for  the  accumulation  of  sewage 
matter  nor  ridges  to  obstruct  the  flow  through 
the  drain.  With  the  object  of  facilitating  the 
making  of  a  concentric  joint,  pipes  are  fre- 
quently tapered  at  the  spigot  or  provided  with 
excrescences  in  the  socket  which  answer  well 
if  the  pipes  are  carefully  made  and  burned. 


Some  makers  (as  in  the  Stanford  joint)  provide 
a  ring  of  plastic  composition  round  the  spigot 
and  in  the  socket,  which  answers  the  same 
purpose  and  which  is  capable  of  making  a 
joint  in  itself  if  greased  with  a  mixture  of 
tallow  and  rosin.  Such  a  joint  cannot  entirely 
be  relied  on,  and  should  be  used  only  in  con- 
junction with  a  cement  joint.  In  other  cases, 
such  as  Hassall's  joint,  similar  bands  are  so 
arranged  that  when  the  pipes  are  put  together 
a  mould  is  formed  in  the  interior  of  the  socket 
which,  when  filled  with  liquid  cement  through 
a  hole  in  the  wall  of  the  socket,  forms  a  reliable 
joint. 

Pipes,    Weights    and    Dimensions   of 
Cast-iron,  for  various  purposes  :— 

LIGHT  (WASTE  AND  VENT  PIPES). 


Diameter 

Thickness 

Length 

Diameter 

Length 

Wei  gilt 

of  pipe 

of  pipe 

of  pipe 

of  socket 

of  socket 

of  pipe 

in  inches. 

in  inches. 

in  feet. 

in  inches. 

in  inches. 

in  11>. 

2 

A 

6.0 

84 

2i 

26.0 

2i 

A 

6.0 

8f 

2j 

28.0 

3 

A 

6.0 

4 

3" 

36.0 

3| 

A 

6.0 

4£ 

3 

40.0 

4 

A 

6.0 

4 

3f 

46.0 

4£ 

A 

6.0 

5f 

4! 

54.0 

5 

A 

6.0 

4 

4| 

60.0 

MEDIUM  (SOIL  AND  WASTE  PIPES). 


Diameter 

Thickness 

Length 

Diameter 

Length 

Weight 

of  pipe 
in  inches. 

of  pipe 
in  inches. 

of  pipe 
in  feet. 

of  socket 
in  inches. 

of  socket 
in  inches. 

of  pipe 
in  Ib. 

2 

. 

. 

6.0 

31 

2| 

34.0 

3 

6.0 

4 

31 

48.0 

3£ 

6.0 

4} 

8| 

54.0 

4 

6.0 

6| 

4 

60.0 

4* 

; 

6.0 

5| 

4 

70.0 

5 

6.0 

6} 

4| 

80.0 

6 

"' 

6.0 

7J 

4f 

98.0 

HEAVY  (SoiL  AND  DRAIN  PIPES). 


Diameter 

Thickness 

Length 

Diameter 

Length 

Weight 

of  pipe 

of  pipe 

<if  pipe 

of  socket 

of  socket 

of  pipe 

in  inches. 

in  inches. 

in  feet. 

in  inches. 

in  inches. 

in  11). 

3 

A 

6.0 

4* 

81 

7.00 

8i 

| 

6.0 

5 

3* 

8.00 

4 

I 

6.0 

5* 

32 

9.00 

4* 

R 

6.0 

6|C 

8f 

118.0 

5 

| 

6.0 

6$ 

4 

130.0 

6 

I 

6.0 

?! 

4 

150.0 

318 


PIP 


MUNICIPAL   AND    SANITAEY  ENGINEEEING. 


PLU 


CAMERON  AND  ROBERTSON. 

SPIGOT    AND    SOCKET    PIPES    FOR   WATERWORKS  FOR 
300  FT.  WORKING  HEAD.    TESTED  TO  600  FT. 


Bore. 

Thickness 
of  Metal. 

Length 
exclusive  of 
socket. 

Average  Weight 
per  Pipe. 

Inches. 

Inches. 

Feet. 

Cwt. 

Qrs. 

Lbs. 

2 

§ 

6 

— 

2 

4 

2J 

| 

9 

1 

0 

0 

3" 

I 

9 

1 

0 

10 

4 

£ 

9 

2 

0 

0 

5 

\ 

9 

2 

1 

7 

6 

\ 

9 

2 

3 

14 

7 

\ 

9 

3 

1 

0 

8 

| 

9 

3 

2 

23 

9 

A 

9 

4 

2 

24 

10 

A 

9 

5 

0 

16 

12 

t 

9 

6 

3 

13 

15 

*t 

9 

9 

2 

3 

18 

9 

13 

1 

12 

24 

/ 

9 

28 

1 

23 

Pipes,  Weights 
Stoneware : — 


and    Dimensions  of 


Diameter 
of  pipe 
in  inches. 

Thickness 
of  pipe 
in  inches. 

Length 
of  pipe 
in  feet. 

Depth 
of  socket 
in  inches. 

Diameter 
of  socket 
in  inches. 

Weight  of 
2-ft.  pipe 
in  Ibs. 

3 

1 

2 

u 

41 

12 

4 

^ 

2 

ll 

5£ 

17 

5 

1 

2 

If 

6| 

22 

6 

i& 

2 

If 

8 

33 

9 

12 

! 

2 

2 

2 
2 

15* 

50 

85 

15 

i* 

2  to  3 

2i 

18f 

124 

18 

M 

2  to  3 

2| 

21| 

190 

Plenum  System. — A  system  of  ventilation, 
the  principle  of  which  is  to  force  fresh  air  into 
a  room  and  draw  the  vitiated  air  out  by 
mechanical  means. 

Plumbing. —  Plumbing  (Internal)  —  Buried 
Pipes — Materials  for  Water  Pipes  and  Fittings 
for  Soil,  Waste  and  Ventilation  Pipes — Cisterns — 
Ball-valves  —  Overflows — Stop  and  Bib-cocks- 
Joints  for  Lead  Pipes — Joints  for  Connecting  Lead 
to  Iron  or  Stoneware — Fixing  of  Pipes — Sanitary 
Appliances  and  Trapping— Unsealing  of  Traps— 
Anti-siphon  Pipes — Puff  Pipes — Soil  Pipes  — 
Waste  Pipes — Water-Waste  Preventers — Flush 
Pipes. 

INTERNAL  PLUMBING.  —  That  plumbing, 
particularly  in  connection  with  water  supply 


319 


and  sanitation,  has  a  considerable  influence 
upon  health  is  now  well  understood.  Whereas, 
until  recently,  so-called  sanitary  appliances 
were  frequently  placed  in  obscure  and  badly 
lighted  positions,  it  is  now  universally 
demanded  that  pipes  and  fitments  should 
be  easily  accessible  and  sanitary  appliances 
placed  in  well-lighted  and  ventilated  positions 
and  concentrated  as  far  as  possible.  The 
practice  of  allowing  water  service,  soil,  and 
waste  pipes  to  be  buried  in  walls,  laid  under 
floors,  or  in  other  "  out  of  sight  "  positions,  is 
objectionable  and  frequently  attended  with 
danger.  Leakages,  burst  pipes,  &c.,  not  only 
cause  unnecessary  damage,  but  incur  much 
cutting  away  and  making  good  ;  moreover, 
chisels,  nails,  &c.,  are  often  accidentally  driven 
into  such  pipes,  which,  in  the  case  of  soil  or 
ventilation  pipes,  may  remain  undiscovered  for 
some  time,  meanwhile  being  a  menace  to  the 
health  of  the  occupants.  Of  sanitary  appli- 
ances, the  present  demand  is  for  fittings  with 
a  minimum  of  mechanism  and  fouling  surface, 
and  such  that  the  whole  may  be  easily  cleansed. 
It  is  as  well  to  point  out,  however,  that  unless 
such  fittings  are  placed  in  positions  wherein 
the  surrounds  are  both  visible  and  accessible, 
it  is  doubtful  whether  the  absence  of  an 
inclosure  is  advantageous.  Plumbing,  to  be 
carried  out  in  a  proper  manner,  requires  skilled 
craftsmanship  and  attention  to  a  number  of 
details,  as  will  be  more  readily  understood  from 
the  following  : — 

ESSENTIAL  CONDITIONS  AND  DETAILS  OF 
PLUMBING  :  SELECTION  OF  MATERIALS. — The 
characteristic  of  the  water  supply  should  be 
considered.  Most  soft  waters  have  a  solvent 
action  on  lead  and  zinc,  rendering  the  use  of 
these  metals  dangerous.  Iron  is  also  affected 
by  soft  water  to  such  an  extent  that  dis- 
coloration of  baths,  lavatories,  and  domestic 
utensils  follows,  as  well  as  corrosion  of  the 
pipes,  &c.  Tin  is  the  best  metal  for  use  with 
such  water,  tin-lined  iron  and  lead  pipes  being 
extensively  used  for  this  purpose.  For  large 
pipes,  iron  coated  with  Dr.  Angus  Smith's 
solution  is  satisfactory  ;  for  hot  water  supply, 
copper  should  be  used  throughout.  Practically 


FLU 


PLU 


any  metal  may  be  used  for  hard  water,  the 
calcium  carbonates  of  which  quickly  coat  the 
pipes,  effectually  preventing  any  solvent  action. 
The  selection  of  materials  for  soil,  waste,  and 
ventilation  pipes  is  influenced  by  cost,  exposure 
to  damage  and  theft,  expansion  and  contraction 
likely  to  arise,  either  from  solar  heat  or  by  the 
passage  of  liquids  through  the  pipes.  Brass- 
work  and  other  fittings  should  be  of  good 
quality,  remembering  the  adage  "  the  cheapest 
is  the  best  of  its  kind." 

PIPES. — All  pipes  should  be  placed  in  acces- 
sible positions,  and  as  far  as  possible  where 
unaffected  by  frost;  where  exposure  is  un- 
avoidable they  should  be  protected  by  an 
efficient  covering ;  water  services  should  be 
so  arranged  as  to  enable  the  whole  of  the 
pipes  to  be  easily  emptied  during  severe 
weather  or  when  the  premises  are  unoccupied. 
All  pipes  should  be  well  supported  and  bends 
made  to  an  easy  radius.  In  the  case  of  hot- 
water  pipes  adequate  allowance  should  be 
provided  for  expansion,  and  when  necessary  to 
pass  through  walls  or  floors  sleeves  should  be 
provided.  Lead  pipes  should  not  be  placed 
in  contact  with  lime  or  cement,  nor  should 
any  metal  pipe  be  laid  in  ground  composed  of 
ashes  or  similar  refuse  without  being  sur- 
rounded with  a  suitable  protective  material. 
All  pipes  should  rise  to  allow  air  to  auto- 
matically pass  out,  either  through  the  cistern 
or  some  fitting  such  as  a  ball-valve  or  tap,  or, 
in  the  case  of  a  hot-water  apparatus,  the 
expansion  or  open  pipe.  Underground  pipes 
should  be  kept  about  2  ft.  6  in.  below  the 
surface  to  prevent  the  water  freezing. 

CISTERNS. — Cisterns  should  be  placed  in 
well-lighted,  ventilated,  and  warm  positions, 
and  be  provided  with  covers.  Although  the 
water  for  dietetic  purposes  should  be  drawn 
direct  from  the  main,  cisterns  are  necessary 
for  the  hot-water  supply l  and  to  provide 
storage  for  sanitary  appliances.  The  absence 
of  cisterns  in  the  latter  case  occasions  much 
discomfort  should  the  public  supply  be  turned 

1  In  Canada  and  some  parts  of  the  United  States  of 
America  the  cold  water  supply  is  connected  direct 
from  the  main  to  the  hot-water  apparatus. 


oft'  for  repairs,  &c.  Lead  or  other  safes  should 
always  be  provided  under  cisterns  placed  over 
ceilings  and  where  a  leakage  would  cause 
damage ;  condensation  on  the  sides  of  cisterns 
and  pipes  often  gives  rise  to  a  supposed 
leakage.  Owing  to  the  affinity  of  water  for 
gases,  cisterns  and  also  the  overflows  there- 
from should  not  be  placed  near  the  ends  of 
soil,  waste,  or  ventilation  pipes,  or  in  any 
position  where  impure  air  may  have  access. 

BALL-VALVES. — Ball-valves  should  be  pro- 
perly fixed,  either  to  the  top  of  the  cistern  or 
the  wall  immediately  above,  or  passed  through 
the  side  of  cistern  and  made  secure  with  a 
back-nut.  Confusion  often  results  from  the 
terms  "high"  and  "low"  pressure  ball- 
valves.  A  ball-valve  with  a  restricted  orifice 
exposes  a  smaller  area  to  the  pressure  of  water 
within  the  pipe  than  a  full-bore  valve,  the  sum 
of  the  moments  required  to  ensure  the  valve 
closing  being  proportionately  less.  Briefly, 
a  "high-pressure  "  ball-valve  has  a  restricted 
orifice,  a  "  low-pressure  "  being  full-way  or 
full-bore.  Ball-valves  of  the  full-bore  type, 
in  which  the  moments  are  increased  by  com- 
pound levers  and  also  those  of  the  "  equilib- 
rium "  pattern  are  obtainable  ;  in  the  latter, 
the  water  presses  on  each  side  of  the  piston 
or  jumper.  These  valves  are  used  on  both 
high  and  low  pressures. 

OVERFLOWS. — Overflows  should  be  large 
enough  to  take  away  the  water  when  the  valve 
is  full  open.  The  diameter  should  bear  some 
proportion  to  the  size  of  the  supply  pipe  and 
the  pressure  therein,  and  should  in  all  cases 
be  at  least  50%  larger  in  diameter  than  the 
inlet.  It  is  a  common  occurrence  for  ball- 
valves  to  become  fixed,  especially  during  the 
emptying  of  cisterns ;  it  is  also  frequently 
found  that  the  ball  is  filled  with  water,  when 
it  fails,  of  course,  to  float ;  a  further  risk  is 
that  of  the  ball  becoming  detached  from  the 
lever.  In  each  instance  the  valve  may  remain 
full  open,  and,  failing  the  provision  of  an 
adequate  overflow,  result  in  much  damage.  It 
is  necessary  to  protect  the  ends  of  large  over- 
flows to  prevent  birds  building  therein.  Valves 
when  fixed  on  the  ends  of  overflows  should  be 


320 


PLU 


MUNICIPAL   AND    SANITAEY  ENGINEERING. 


PLU 


light  and  work  freely  to  avoid  obstruction  or 
failure  to  open  at  the  desired  moment. 

STOP-  AND  BIB-COCKS. — Stop  and  bib-cocks 
of  the  screw-down  type  are  generally  insisted 
upon  by  the  various  water  authorities ;  by 
their  use  the  risk  of  breakage  of  pipes  by 
shock  or  the  setting  up  of  water-hammer  (a 
chattering  of  ball-valves)  is  reduced.  Such 
valves  are  also  more  easily  repaired  and  are 
more  economical  in  use  than  plug  valves, 
although  the  latter  are  largely  used  and  pre- 
ferred in  many  establishments  owing  to  the 
water  issuing  full-bore  by  giving  the  handle 
a  half-turn.  Quick-turn  screw-down  valves 
are  frequently  fitted  to  lavatory  basins,  the 
spindle  being  screwed  to  a  quicker  pitch, 
these  valves  are  preferred  on  the  same 
grounds  as  plug  valves.  Spring  or  cam-action 
valves  are  also  frequently  used  for  lavatory 
basins,  mainly  to  prevent  waste  of  water ; 
they  are  more  liable  to  get  out  of  order  and 
more  difficult  to  repair.  Stop-cocks  should  be 
fitted  to  all  services — on  the  main  pipe  before 
or  immediately  it  enters  the  premises,  and  on 
down  services  as  close  to  the  cistern  as  pos- 
sible. In  the  latter  case  they  should  be 
labelled  with  the  fittings  controlled.  Full- 
way,  or,  as  they  are  also  termed,  Gate  or 
Feet's  valves  offer  the  least  obstruction  to  the 
passage  of  water.  Very  often  such  valves  do 
not  close  so  tight  as  the  ordinary  pattern 
"  screw-down  "  valve.  For  use  on  lead  pipes 
many  prefer  to  use  stop-cocks  with  unions 
thereby  facilitating  the  taking  out  of  the  body 
of  the  valve  should  necessity  arise,  and  also 
to  prevent  the  body  of  the  valve  being  heated 
during  soldering.  When  such  stop-cocks  are 
placed  underground  there  is  a  risk  of  leakage 
at  the  unions  ;  for  this  reason  "  tinned-end  " 
stop-cocks  are  often  preferred.  Stop-cocks 
should  be  fixed  on  all  important  branches, 
and  wherever  repairs  would  cause  incon- 
venience by  the  shutting  off  of  water  to  other 
parts  of  the  premises.  Bib-cocks  should  be 
securely  fixed,  and  in  the  case  of  sinks  at  a 
sufficient  height  to  pass  a  pail  under,  the 
usual  height  being  14  in. 

JOINTS    FOR   LEAD    PIPES. — -The   only   per- 


missible joint  for  lead  pipes,  unless  used  for 
acids,  is  the  wiped  soldered  joint.  In  all 
wiped  joints  to  lead  pipes  the  prepara- 
tion consists  of  forming  a  socket  and  spigot, 
care  being  taken  that  the  bore  is  not 
obstructed  and  that  the  spigot  points  in  the 
direction  of  flow,  thus  avoiding  an  edge  for 
the  water  to  impinge  against.  The  pipe  for 
a  few  inches  on  each  side  of  the  joint  is 
coated  with  "  soil " — a  mixture  of  vegetable 
black  and  size  or  glue — to  prevent  solder 
adhering  to  the  pipe  ;  that  portion  of  the  pipe 
to  be  soldered  is  then  "  shaved  "  bright  and 
"  fluxed."  After  the  pipe  has  been  sufficiently 
warmed  and  a  body  of  solder  at  a  suitable 
temperature  is  attached  to  the  joint,  the 
plumber  shapes  and  completes  the  joint  with 
the  aid  of  a  cloth  (made  of  a  number  of 
thicknesses  of  moleskin  cloth).  Should  the 
joint  be  in  a  difficult  position  or  of  a  large 
size  the  solder  is  kept  warmed  up  whilst 
wiping  by  the  aid  of  a  "plumbing  iron" 
heated  to  a  dull  redness. 

LENGTH  OF  WIPED  JOINTS  AND  SOLDER 
REQUIRED. — The  length  of  joints  varies  in  dif- 
ferent localities  and  with  different  workmen. 
In  London  the  lengths  are  approximately  as 
follows :  — 


%  in.  pipe  . 
|  in.  to  3  in. 
3^  in.  upwards 


3    in. 
SJin. 


There  is  no  exact  rule  for  calculating  the 
quantity  of  solder  required  for  wiped  joints ; 
this  depends  largely  upon  the  preparation ; 
moreover,  workmen  vary  very  much  in  the 
quantity  of  solder  left  on  joints ;  much  is 
also  unavoidably  lost  during  heating  and  use. 
A  fair  estimate  for  general  work  is  to  allow 
1  Ib.  per  inch  bore  of  pipe ;  thus  for  a  2  in. 
pipe  allow  2  Ibs.,  for  a  3  in.  3  Ibs.,  and  so  on. 
Obviously  a  heavier  joint  is  required  on  pipes 
to  withstand  high  pressure  than  is  the  case 
with  soil  and  waste  pipes. 

DETAILS  OF  SOLDERED  JOINTS. — Fig.  1 
shows  a  wiped  soldered  joint  as  made  for  con- 
necting up  lengths  or  runs  of  pipe;  such 
joints  are  termed  "  running  joints."  These 


M.S.E. 


321 


PLU 


ENCYCLOPEDIA   OF 


PLU 


joints  may  be  made  in  any  position  ;  when 
sufficiently  horizontal  to  enable  the  solder  to 
be  poured  thereon  from  a  ladle,  they  are  said 
to  be  made  "  underhand."  Where  this  is  not 
possible  or  convenient  owing  to  the  pipe  being 
in  a  vertical  position,  the  solder  is  splashed 
on  and  the  joint  is  said  to  be  made  "  upright." 


body  of  the  pipe ;  the  ends  of  the  pipe  to  be 
soldered  should  be  tinned  before  being  put 
together.  Similar  joints  are  made  to  lead 
pipes  when  passing  through  lead  flats,  safes, 
&c.,  the  leadwork  of  which  takes  the  place  of 
the  lead  collar.  The  taft  or  block  joint  is 
not  so  reliable  as  the  ordinary  wiped  joint,  as 


FIG.  1. 


FIG.  2. 


FIG.  7. 


FIG.  8. 


FIG.  4. 


FIG.  3. 


FIG.  5. 


FIG.  9. 


FIG.  9. 


FIG  6. 


FIG.  10. 


Soldered  Joints. 


1.  Wiped  "Running  Joint."  2.  Branch  Joint.  3.  Cross  Section  of  Branch  Joint.  4.  Taft  or  Block  Joint. 
5.  Expansion  Joint  for  External  Waste  Pipes.  6.  Outlet  Joint.  7.  Astragal  Joint.  8.  Copper  Bit  or  Blown 
Joint.  9.  Joint  Connecting  Lead  to  Iron  Drain  ;  also  Stoneware  Drain.  10.  Gun  Metal  Thimble  and  Joint  to  W.C. 


Figs.  2  and  3  show  a  soldered  branch  joint ; 
an  important  detail  is  the  working  up  of  the 
sides  of  the  main  pipe  until  they  stand  up 
about  f  in.  above  the  top  of  the  same  to  form 
a  socket  for  the  branch  pipe.  Fig.  4  shows 
a  taft  or  block  joint;  such  joints  are  frequently 
used  on  pipes  fixed  in  chases.  The  socket 
pipe  should  stand  up  well  above  the  lead 
collar  to  permit  of  solder  adhering  to  the 


322 


Fig.  1,  since  it  is  possible  for  the  joint  to 
present  a  good  appearance,  whereas  the  solder 
may  not  be  properly  attached  to  the  pipe. 
For  this  reason,  ordinary  wiped  joints  are 
often  advocated,  blocks  and  collars  being 
provided  between  the  joints  for  the  purpose 
of  support.  Fig.  5  shows  an  expansion  joint 
for  external  lead  waste  pipes.  (Whenever  lead 
waste  pipes  are  fixed  with  rigid  joints  and  hot 


FLU 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


PLU 


and  cold  water  alternately  passes  through, 
fracture  will  sooner  or  later  occur.)  These 
expansion  joints  are  prepared  by  driving  in 
a  mandril  to  swell  out  the  pipe  to  form  a 
socket  of  the  required  size,  the  other  end  of 
the  length  is  opened  to  slide  freely  in  the 


FIG.  11.— Gun  Metal  Thimble 
with  Anti-Siphon  Branch. 

socket  of  the  lower  length,  and  to  ensure  a 
proper  alignment,  a  bead  may  be  turned  for 
the  same  purpose.  The  pipes  on  which  these 
joints  are  made  should  not  exceed  6  ft.  in 
length,  as  obviously  the  fixings  should  be  at 
the  top  end  only;  such  fixings  usually  take 
the  form  of  lead  tacks  strongly  soldered  to  the 
back  of  the  socket.  Ornamental  beads 
(astragals)  are  often  soldered  on  the  socket  to 
improve  the  appearance.  Prior  to  fixing  the 


FIG.  12.— Gun  Metal  Thimble 
with  Anti-Siphon  Arm  for 
"  Turn  Down  "  Closets. 

pipes,  india-rubber  rings  are  slipped  on  the 
spigot.  It  is  important  that  sufficient  room 
be  left  between  the  end  of  pipe  and  bottom  of 
socket  for  expansion.  Fig.  6  shows  the  form  of 
joint  for  overflow  and  outlet  pipes  to  cesspools, 
&c.,  a  sinking  being  made  in  the  woodwork 
into  which  the  lead  is  dressed ;  a  bead  is 
turned  on  the  end  of  the  pipe  and  the  whole 


323 


soldered  together.  Fig.  7  shows  an  astragal 
joint  as  frequently  made  on  lead  soil  and 
ventilation  pipes.  These  joints  are  not  so 
strong  as  ordinary  soldered  joints ;  they  are 
made  with  fine  or  copper  bit  solder,  the  actual 
joint  being  similar  to  a  copper  bit  joint.  As 
such  joints  are  generally  made  in  position,  a 
blow-lamp  is  employed,  and  much  care  has  to 
be  exercised  to  prevent  fusing  of  the  pipe  or 
loosening  of  the  solder  holding  the  mouldings 
or  astragals.  The  only  point  in  favour  of 
such  joints  is  that  the  appearance  resembles 
the  sockets  of  rain-water  pipes.  Fig.  8  shows 
a  copper  bib  or  blown  joint  as  employed  on 
lead  and  composition  gas  pipes,  and  on  the 
cheapest  of  so-called  plumbing.  Fig.  9  shows 
a  form  of  joint  for  connecting  lead  to  iron  or 
stoneware,  the  bore  of  the  thimble  or  sleeve 
being  equal  to  the  external  diameter  of  the 
lead  pipe.  Fig.  10  shows  a  thimble  as  con- 
nected to  a  P  trap  of  a  pedestal  closet.  These 
short  thimbles  permit  the  anti-siphon  pipe  to 
be  connected  near  the  head  of  the  trap. 
Fig.  11  shows  a  thimble  with  anti-siphon  branch 
cast  on,  and  insures  the  same  being  connected 
close  to  the  head  of  trap.  Fig.  12  shows  a 
thimble  for  use  with  pedestal  closets  provided 
with  turn-down  or  S  traps.  An  advantage  of 
these  thimbles  is  that  the  joint  of  the  anti- 
siphon  pipe  is  stronger  than  when  simply 
socketed  into  the  out-go  of  trap,  and  also 
enables  the  pan  and  trap  to  be  removed  with- 
out interfering  with  the  anti-siphon  pipe — an 
important  feature  when  a  pan  has  to  be 
replaced.  These  thimbles  also  insure  the 
anti-siphon  pipe  being  connected  on  the  leg, 
and  not  on  the  crown  of  the  trap,  where  it 
would  be  liable  to  become  choked. 

FIXINGS  FOR  LEAD  PIPES. — Lead  pipes  may 
be  fixed  by  any  of  the  following  methods  : 
Lead  tacks,  as  shown  in  Fig.  13.  These 
tacks  consist  of  stout  sheet  lead,  or  they  may 
be  cast  of  any  desired  shape  ;  when  of  sheet 
lead  they  are  usually  made  of  twice  the  width, 
being  then  turned  back  over  the  hooks  or 
nails.  The  essential  points  are :  that  the 
tacks  should  be  stout — equal  to,  say,  10  Ibs. 
lead — and  of  a  good  length  to  enable  the  pipe 


Y  2 


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to  be  well  supported,  but  which  also  depends 
upon  a  good  width  and  body  of  solder  adhering 
to  the  pipe  and  tack ;  for  this  reason  the  tack 


© 


© 


FIG.  13.— Lead  Tack.. 

requires  to  be  well  bent  up  or  bevelled  close  to 
the  pipe.  On  soil  pipes  and  the  like  the  tacks 
present  a  better  appearance  when  fixed  in 
pairs,  5  ft.  apart.  The  tacks  described  are 


FIG.  14. — Cast-Iron  Bracket  supporting 
Lead  Soil  Pipe. 

known  as  "  back  tacks."  When  tacks  are 
soldered  on  the  front  they  are  known  as 
"  face  tacks,"  and  are  held  by  many  to  be  the 
stronger  of  the  two ;  face  tacks  are  largely 
used  for  service  pipes.  Cast-iron  brackets : 


soil,  ventilation,  and  waste  pipes  are  some- 
times fixed  by  passing  them  through  a  cast- 
iron  bracket,  as  shown  in  Fig.  14,  a  lead  collar 
being  wiped  on  as  described  in  taft  or  block 
joints.  Service  pipes  are  frequently  fixed 
with  pipe  and  wall  hooks ;  these  hooks 
should  be  strong  and  a  piece  of  sheet  lead 
placed  behind  the  tang  to  prevent  injury 


FIG.  15. — Lead  Pipe  supported  on 
Wooden  Fillet. 


to  the  pipe.  It  is  important  that  horizontal 
pipes  be  well  supported  to  prevent  sagging 
and  ultimate  breakage.  Where  possible, 
horizontal  lead  pipes  are  best  supported  on 
fillets,  as  shown  in  Fig.  15. 

SANITARY  APPLIANCES  AND  TRAPPING.  —  All 
sanitary  appliances  should  be  trapped  as  close 
to  the  fitting  as  possible,  and  all  such  traps 
should  f  be  of  a  material  which  lends  itself  to 
sound  jointing ;  they  should  also  possess  a 
smooth  interior,  sufficiency  of  water  seal,  and 
the  shape  should  be  such  as  to  resist  siphon- 
age  by  momentum.  In  addition,  the  inlets  of 
all  traps  should  be  at  least  equal  to  the 
sectional  area  of  the  water  in  the  trap,  the 
body  of  which  should  be  contracted  to  hold  a 
minimum  quantity  of  water  compatible  with 
efficiency.  The  outlets  to  baths,  sinks,  lava- 
tories, and  similar  fitments  should  be  of  a 
size  equal  or  larger  than  the  trap,  and  possess 
a  clear  way.  Traps  of  the  round  pipe,  or 
those  of  the  anti-D  shape,  are  alone  permissible 


324 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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for  sanitary  appliances.  Lead  traps  possess 
a  smooth  interior,  and  are  easily  jointed  to 
the  fittings  and  waste.  Traps  of  cast  iron 
and  brass  are  also  used  on  sanitary  appliances, 
and  care  should  be  taken  to  insure  that  the 
same  have  a  smooth  interior.  The  best  forms 
are  vitreous  or  glass  enamelled  inside ;  the  ends 
may  be  screwed  for  connecting  to  iron  or 
other  materials,  or  provided  with  a  union  for 
soldering  to  lead. 

Loss  OF  WATER  SEAL. — Traps  may  be 
rendered  futile  by  (a)  evaporation  of  the  con- 
tained water ;  (b)  momentum,  as  when  the 
momentum  of  the  water  passing  through  the 
trap  is  so  great  as  to  leave  an  insufficiency  of 
water  to  re-seal  the  trap  ;  (c)  siphonage,  caused 
by  unequal  atmospheric  pressure  on  the 
surfaces  of  the  water  in  trap,  which  may  be 
caused  when  water  passes  down  an  unventi- 
lated  soil  or  waste  pipe,  the  falling  water 
tending  to  leave  a  vacuum  behind,  or  when 
a  discharge  of  water  passes  by  an  unventilated 
branch  pipe,  pulling  some  of  the  air  with  it ; 
(d)  waving  out  or  oscillation,  caused  by  alter- 
nations of  pressure  on  the  surface  of  water  in 
out-go  of  trap,  imparting  a  waving  motion  to 
the  water  therein,  a  small  quantity  passing 
over  the  weir  at  each  oscillation.  This  action 
may  be  caused  by  a  "  blow-down,"  or  by  the 
discharge  from  a  distant  fitting  compressing 
the  air  in  the  branch  to  which  the  trap  is 
connected  ;  (c)  capillarity,  as  when  pieces  of 
cloth,  hair,  or  other  fibrous  material  lodge  on 
the  weir  of  trap;  water  passes  up  such  matters 
as  oil  up  a  lamp-wick,  the  seal  being 
ultimately  destroyed.  Traps  may  also  be 
unsealed  by  compression  of  gases,  as  when 
storm  water  rises  in  sewers,  or  when  the 
temperature  of  air  in  unventilated  pipes  is 
raised. 

ANTI-SIPHON  PIPES. — These  are  pipes  fixed 
to  prevent  loss  of  water  seal  in  traps,  and  to 
ventilate  the  branch  pipes.  To  be  effective 
they  should  be  connected  within  3  in.  to  12  in. 
of  the  head  of  the  trap ;  if  connected  nearer 
the  head  there  is  danger  of  matters  washing 
up  the  same,  if  connected  at  any  distance 
further  than  12  in.  from  the  head  the  pipe 


may  not  properly  prevent  siphonage.  The 
diameter  of  the  pipe  should  not  be  less  than 
1J  in.  in  the  case  of  waste  pipes,  nor  less  than 
2  in.  in  the  case  of  soil  pipes.  Where  there 
is  a  probability  of  the  waste  or  soil  pipe  being 
fully  charged  with  water  it  is  best  to  increase 
the  size  of  the  anti-siphon  pipes ;  in  fact, 
with  baths  fitted  with  full-way  wastes  the 
anti-siphon  pipe  would  be  better  if  of  the 
same  diameter  as  the  waste.  Where  a  number 
of  anti-siphon  pipes  are  connected  together, 
the  diameter  of  the  main  pipe  should  be 
increased. 

PUFF-PIPES. — These  are  anti-siphon  pipes 
which  terminate  on  the  face  of  the  wall 
instead  of  being  carried  up  to  the  roof  level  or 
branched  into  the  main  stack  ;  obviously  puff- 
pipes,  if  used  at  all,  should  only  be  used  in 
connection  with  waste  pipes ;  where  such  pipes 
are  used,  care  should  be  taken  that  the 
open  end  is  well  away  from  windows,  &c. 
Practically  speaking,  puff-pipes  are  objection- 
able, and  are  only  used  where  the  expense  of 
carrying  a  pipe  up  to  above  roof  level  is  con- 
sidered too  great.  The  pipe  between  the  valve 
and  trap  in  valve-closets  is  also  termed  a 
puff-pipe,  and  also  the  pipe  between  the  traps 
of  some  makes  of  siphonic  closets  ;  in  each 
case  they  should  terminate  on  the  face  of  the 
wall. 

SOIL  PIPES. — Materials  for  soil  and  ventila- 
tion pipes  are  practically  confined  to  lead  and 
iron.  Zinc  and  sheet-iron  pipes  should  not 
be  permitted,  owing  to  the  rapid  corrosion  of 
these  materials  when  in  the  presence  of 
moisture  and  drainage  gases.  Drawn  lead 
pipe  of  a  substance  equal  to  7  Ibs.  lead,  and 
iron  j3^  in.  to  \  in.  thick,  practically  form  the 
basis  of  the  L.  C.  C.  by-law  respecting  soil 
pipes. 

LEAD  SOIL  PIPES. — Lead  pipes  2  in.  and 
upwards  are  usually  made  in  10  ft.  lengths, 
and  may  be  obtained  of  any  substance  up  to 
10  Ibs.  lead.  Although  7  Ibs.  lead  is  practi- 
cally the  minimum  substance  allowed  by  the 
L.  C.  C.,  8  Ibs.  is  to  be  preferred ;  whilst  10  Ibs. 
is  frequently  fixed.  Lead  is  for  all  practical 
purposes  the  best  material  for  soil  and  venti- 


325 


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lation  pipes.  Amongst  its  advantages  are  : 
the  ease  with  which  it  may  be  bent  and  fitted 
to  any  position,  smoothness,  few  and  sound 
joints,  and,  when  properly  ventilated,  immunity 
from  corrosion.  Owing  to  possible  damage 
by  solar  rays,  a  position  sheltered  from  the 
sun  should,  if  possible,  be  selected.  Lead 
cannot  be  advocated  for  soil  pipes  through 


Q 


FIG.  16. — Arrangement  of  Soil  and  Ventilation 
Pipes. 

which  hot  and  cold  water,  as  from  slop-sinks, 
is  alternately  passing,  unless  some  form  of 
expansion  joint  is  used.  Fig.  16  shows 
the  arrangement  of  soil,  branch,  and  ventila- 
tion pipes  suitable  for  various  conditions. 
The  termination  of  anti-siphon  pipe  may 
be  branched  into  the  soil  pipe  a  few  feet  above 
the  top  closet  or  branch,  or  may  be  carried  up 
to  the  same  height  as  the  soil  pipe.  When 
the  top  of  the  soil  pipe  is  some  considerable 
distance  beyond  the  top  branch,  air  may  more 


easily — owing  to  reduced  friction — reach  the 
branch  to  which  the  trap  is  connected,  if  the 
end  of  the  same  is  branched  into  the  soil 
pipe  instead  of  carrying  up  a  separate  pipe. 
The  open  ends  of  soil  pipes  should  be 
placed  well  away  from  windows,  or  any 
opening  to  the  house,  and  be  carried  well 
above  the  eaves  of  the  roof.  Owing  to  the 
affinity  of  water  for  gases,  care  should  be 
taken  to  insure  the  ends  being  well  away 
from  cisterns.  As  air  should  be  able  to  pass 
down  soil  pipes  whenever  a  fitting  thereon  is 
flushed,  air-extracting  cowls  should  not  be 
placed  on  the  ends.  (Details  of  joints  and 
methods  of  fixing  pipes  will  be  found  under 
their  respective  heads.) 

IRON  SOIL  PIPES. — Iron,  on  account  of 
cheapness  and  hardness  of  material,  is  largely 
used  for  soil  and  ventilation  pipes  ;  the  pipes 
should  be  of  good  substance,  approximately 
^  in.  thick,  be  well  protected  from  corrosion, 
and  the  sockets  made  deep,  and  with  a  suffi- 
cient annular  space  for  caulking.  All  iron 
pipes  are  best  fixed  clear  of  the  wall,  either  on 
"  holderbats  "  or  brackets.  The  joints  are 
best  made  with  molten  lead  properly  caulked. 
It  is  best  to  dispense  with  the  use  of  yarn, 
using  lead  rope  or  lead  wool  instead.  The 
interior  of  the  pipes  should  be  examined  for 
obstructions  and  smoothness.  When  cast- 
iron  soil  pipes  are  used  it  is  usual  to  connect 
the  closet  to  the  same  by  a  brass  or  gun-metal 
thimble  wiped  on  to  a  piece  of  drawn-lead 
pipe,  such  being  compulsory  in  the  L.  C.  C. 
area.  Iron  is  not  a  commendable  material 
for  ventilation  pipes,  owing  to  the  accumula- 
tion of  rust  at  the  base  of  the  pipe  ;  for  this 
reason  lead  is  preferred  by  most  sanitary 
engineers.  Care  should  be  taken  in  cutting 
iron  pipes  to  insure  a  true  cut ;  the  best  tool 
for  this  purpose  being  "  wheel  cutters  "  of  the 
Jones's  type.  Such  a  tool  also  effects  a  saving 
of  time. 

WASTE  PIPES. — The  practice  of  discharging 
waste  pipes  over  hopper  heads  and  over  the 
tops  of  gulley  gratings  is  offensive  and  objec- 
tionable ;  the  aim  in  all  cases  should  be  to 
permit  the  waste  waters  to  enter  and  pass 


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through  the  gulley  and  thence  through  the 
drain  with  the  minimum  of  obstruction  and 
splashing.  With  this  object  modern  practice 
is  to  construct  the  waste  pipes  and  stacks 
thereof  similar  to  soil  pipes,  except  that  the 
lower  end  discharges  under  the  grating,  but 
over  the  water  of  a  gulley  trap  ;  the  main 
stack  being  usually  2  in.  to  3  in.  diameter. 
With  a  single  fitting  on  the  ground  floor  it  is 
more  usual  to  omit  the  stack  and  carry  a  puff- 


FIG.  17.— Sink  with  Trapped  and  Ventilated 
Waste  discharging  into  Back  Inlet  Gulley. 

pipe  up  about  7  ft.  high  (see  PUFF-PIPES)  ; 
care  should  be  taken  to  insure  the  puff-pipe 
terminating  in  a  position  above  the  top  of  the 
fitting  to  which  it  is  connected,  or  it  may  act 
as  an  overflow  in  case  of  stoppage  of  the  waste 
pipe.  Although  the  use  of  puff-pipes  is  better 
than  hopper  heads,  neither  are  so  good  as 
carrying  the  pipe  up  in  the  manner  described. 
The  size  of  waste  pipes  varies  somewhat,  but 
in  no  case  should  they  be  less  than  1^  in. 
diameter.  The  sizes  recommended  being  : 
Lavatories,  l-£  in.  to  1^  in. ;  baths  and  sinks, 
1^  in.  to  2  in.  Lead,  as  in  the  case  of  soil  pipes, 
is  the  best  material  for  general  use;  where  a 
large  quantity  of  hot  water  passes  through  and 
the  pipes  may  be  fixed  outside,  expansion  joints 
as  described  under  "Joints"  should  be  used; 


if  the  pipe  must  of  necessity  be  fixed  inside,  it 
would  be  best  to  use  copper  or  wrought  iron 
properly  protected,  the  lengths  being  con- 
nected with  screwed  sockets  ;  suitable  fittings 
for  connecting  branches  may  be  obtained. 
Cast  iron  with  socketed  joints  is  also  largely 
used  for  waste  pipes ;  they  should  be  smooth 
and  properly  protected,  preferably  glass  or 
vitreous  lined.  Fig.  17  shows  sink  waste  pipe 
fitted  in  the  manner  above  described. 

WATER-WASTE  PREVENTERS.  —  Water-waste 
preventing  cisterns  of  innumerable  designs  are 
obtainable.  The  most  reliable  form,  so  far  as 
flushing  is  concerned,  are  those  in  which  a 
flush  may  be  obtained  whether  the  lever  be 
held  or  released,  such  cisterns  being  those 
provided  with  a  valve  and  siphon  ;  the  holding 
up  of  the  valve  permits  the  water  to  pass 
down  the  flush  pipe,  setting  up  siphonic 
action,  thus  insuring  a  flush  whenever  there 
is  any  water  in  the  cistern.  Many  water 
authorities  object  to  this  type  of  cistern  on 
the  ground  that  a  leakage,  past  the  valve  is 
possible.  In  all  cases  the  cistern  should  fill 
in  60  seconds,  or  thereabouts ;  to  ensure 
this  f  in.  full-way  ball-valves  should  be  fitted 
to  cisterns  under  10  ft.  head  of  water. 

FLUSH  PIPES. — These  may  be  1J  in.  to 
1J  in.  diameter ;  care  should  be  taken  to 
obtain  a  sound  joint  to  the  arm  of  the  w.c. 
pan ;  indiarubber  cones  are  unreliable,  a 
better  form  being  the  lead  cones,  which  may 
be  bossed  up  by  the  plumber  or  purchased 
ready  made. 

To  reduce  the  noise  during  the  filling  of 
the  cistern  a  tube  should  be  attached  to  the 
ball-valve  and  carried  down  to  near  the 
bottom  of  the  cistern,  thus  submerging  the 
end.  The  gurgling  noise  consequent  upon 
the  emptying  of  the  cistern  and  the  inrush 
of  air  may  be  minimised  by  a  valve  arrange- 
ment, which  opens  during  the  emptying  of 
the  cistern,  allowing  air  to  enter  and  check 
the  siphonic  action  before  the  cistern  is  finally 
emptied.  Flushing  cisterns  fixed  just  above 
the  seat  reduce  the  noise  consequent  upon 
emptying ;  such  cisterns  are  specially  made 
for  the  purpose,  and  have  a  larger  outlet 


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to  compensate  for  the  lower  head.  Flushing 
cisterns  are  sometimes  dispensed  with  and 
the  closet  flushed  by  a  valve,  which  permits 
a  predetermined  quantity  of  water  to  pass 
at  each  flush,  somewhat  similar  to  the 
flushing  arrangement  of  many  valve-closets. 
The  size  of  the  supply  pipe  to  these  valves 
depends  upon  the  head  of  water  above  the 
closet.  Cisterns  for  soft  water  are  often 
made  of  wood  and  lead-lined,  brass  fittings 
being  used.  Glass-lined  iron  is  satisfactory 
providing  the  coating  is  properly  applied. 
Glazed  fireclay  cisterns  are  also  used,  but 
as  fireclay  is  of  a  porous  nature  the  sound- 
ness of  the  cistern  depends  upon  the  glaze, 
and  should  the  same  Jbe  chipped  beneath 
the  water  line  and  there  be  any  defect  or 
chipping  on  the  outside,  a  leakage  would 
result.  The  writer  has  had  to  replace  a 
number  of  fireclay  closets  for  a  similar  reason 
and  because  of  the  under  side  of  the  flushing 
rim  being  unglazed,  in  which  case  the  water 
enters  the  fireclay  and  oozes  through  any 
unglazed  part,  frequently  the  screw  holes  and 
under  the  pan.  W.  F. 

Plumbing  (External).  —  Sheet  Lead — 
Weights  of  Lead — Lead  Rain-water  Heads  and 
Spouting — Lead-burning  — Soakers  —  Step-flash- 
ing— Hip  and  Valley  Soakers — Secret  Gutters — 
Roof  Lights — Dormers — Gutters  and  Flats — 
Roof  Cesspools  and  Shoots — Covering  Stone 
Cornices. 

PLUMBING  (EXTERNAL). —  Externally,  the 
principal  work  of  the  plumber  is  to  cover  and 
protect  the  woodwork  of  roofs,  the  lining  of 
gutters,  rendering  watertight  the  junctions  of 
walls,  chimneys,  &c.,  to  roofs,  covering 
of  cornices,  &c.  Sheet  lead  is  mainly 
employed  for  such  purposes  ;  this  on  account 
of  its  durability  and  the  ease  with  which  it 
may  be  "  bossed "  or  worked  to  fit  various 
positions  or  to  take  the  shape  of  the  woodwork 
or  other  material  it  is  to  cover.  The  life  of 
sheet  lead  depends  largely  upon  the  surface  of 
the  material  on  which  it  is  placed  and  the 
manner  in  which  it  is  laid  or  fixed ;  hence  it 
is  important  that  all  woodwork  should  be 


substantial  and  seasoned,  the  boards  of  narrow 
widths  and  laid  in  direction  of  fall ;  all  joints 
should  be  properly  flushed  and  any  angles 
rounded.  Flats,  gutters,  and  the  like  should 
not  be  arranged  with  sharp  falls,  owing  to  the 
tendency  of  lead  to  "  creep  "  (in  specially  steep 
situations,  as  on  hips,  turrets,  &c.,  the  lead 
may  be  easily  fixed  to  prevent  creeping),  nor 
should  the  fall  be  less  than  1  in.  in  10  ft.  To 
prevent  fracture  from  atmospheric  changes, 
sheet  lead  should  always  be  laid  in  as  free  a 
manner  as  possible  consistent  with  security ; 
solder,  except  to  cesspools  and  outlet  pipes, 
should  not  be  used,  but  the  lead  evenly  and 
properly  bossed  to  the  desired  shape.  The 
pieces  should  not  be  of  excessive  size,  and 
nothing  longer  than  10  ft.  permitted  ;  if  pos- 
sible, a  length  approximating  to  7  ft.  would 
be  more  durable.  Drips,  laps,  and  passings 
should  be  deep  or  long  enough  to  prevent 
water  passing  between  the  sheets  by  capillary 
attraction.  The  weights  of  lead  suitable  for 
various  purposes  are  as  under  : 
Soakers  .  .  3  Ibs.  to  4  Ibs.  per  square  foot. 

Stepped  flashings 

Dormer  cheeks  . 

Chimney    and    apron  ^  5  Ibs.  to  7  Ibs. 
flashings 

Coverings  to  cornices. 
Gutters,  flats,  hips,  and  ridges. — Not  less  than 

6  Ibs. 

SHEET  LEAD. — Sheet  lead  may  be  either 
"milled"  or  "  cast,"  and  is  described  by  its 
weight  in  Ibs.  per  square  foot,  and  may  be 
obtained  of  any  weight  in  multiples  of  1  Ib. 
from  3  Ibs.  upwards.  Standard  sheets  are 

7  ft.  wide  and  from  30  ft.   to    40   ft.  long; 
different  widths  up  to  9  ft.  may  be  obtained 
at  a  slightly  increased  cost ;  also  any  substance 
either  in  the  form  of  sheets  or  plates.     The 
usual  stock  weights  are  as  follows  :— 

MILLED  LEAD. 
In  sheets  30  ft.  to  40  ft.  long,  7  ft.  wide. 

3  Ibs.  per  sq  ft.  =  1/20".     Nearest  B.W.G.  18. 
1/15". 

1/12". 
1/10". 
1/9". 
1/8". 


16. 
14. 
12. 
11. 
11. 


328 


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MUNICIPAL   AND    SANITAKY  ENGINEERING. 


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The  thickness  of  sheet  lead  in  inches  may     being  imperative  and  the  holes  strengthened 


be  calculated  by  multiplying  its  weight  in  Ibs. 
per  square  foot  by  '017. 

CAST  LEAD. — Cast  lead  is  sometimes  used 
for  external  plumbing,  especially  upon  reno- 
vations to  medieval  buildings  and  where  it  is 
desired  to  re-use  the  lead ;  in  such  cases  a 
casting  bench  is  usually  fitted  up  on  the  spot. 
Briefly,  the  process  consists  of  carefully 
spreading  a  bed  of  prepared  sand  over  the 
bottom  of  the  casting  bench  (a  wooden  bench 
with  rails  along  the  sides  and  a  tipping  pan 
at  top)  to  a  thickness  of  about  1^  in.,  this  is 
then  slightly  solidified  and  trowelled  to  a 
smooth  surface,  the  lead  being  poured  thereon 
from  the  tipping  pan  at  the  head  of  the  bench, 
the  thickness  being  regulated  by  a  strike— a 
kind  of  straightedge — being  drawn  over  whilst 
the  lead  is  in  a  fluid  condition  ;  the  bottom 
edge  of  the  sheet  is  immediately  cut  off  to 
prevent  fracture  during  contraction.  Cast 
lead,  owing  to  the  natural  positions  of  its 
molecules,  is  less  liable  to  fracture  by  atmo- 
spheric changes  than  milled  lead,  in  which 
the  molecules  are  compressed  during  the 
process  of  "rolling."  Generally  speaking, 
milled  lead  is  capable  of  rather  greater 
manipulation  in  the  hands  of  a  skilful 
plumber.  The  condition  of  lead  work  on  many 
medieval  buildings  furnishes  examples  of  the 
permanency  of  this  metal  either  as  a  roof 
covering  or  for  rain-water  heads  and  spout- 
ing, &c. 

LEAD  RAIN-WATER  HEADS  AND  SPOUTINGS. — 
Cast  lead  was  at  one  period  largely  employed 
for  rain-water  heads  and  spouting ;  cast  iron 
has  of  recent  years  been  substituted  to  a  large 
extent.  There  is  no  comparison  between  the 
life  of  the  two  metals,  and  the  rusting  and 
breaking  of  cast-iron  heads  and  spouting  has 
been  the  cause  of  damage  and  disfigurement 
to  many  buildings,  and  it  is  worthy  of  note 
that  many  architects  are  again  adopting  lead, 
which  adapts  itself  to  more  artistic  develop- 
ment. When  lead  is  used  for  rain-water 
heads  and  spouting,  care  should  be  taken  to 
insure  the  fixings  being  strongly  attached  to 
the  body  of  the  lead,  good  length  ears  or  tacks 


by  increased  thickness  of  material  and  placed 
close  to  the  head  or  spouting.  For  fixing  to 
walls  stout  lead-headed  or  copper  nails  should 
be  used.  Seams  of  lead  heads  and  spouting 
may  be  "  wiped,"  soldered  with  the  aid  of 
soldering  irons,  or  they  may  be  joined  by 
"  burning." 

LEAD  -  BUKNING. —  Lead-burning  or  auto- 
genous soldering  is  the  absolute  fusion  of  the 
pieces  of  lead  one  with  the  other,  no  flux  or 
solder  being  used.  The  pieces  are  first  butted 
together,  or  they  may  be  lapped  over  each 
other  and  the  edges  cleaned  to  remove  any 
oxide ;  an  intense  flame  is  then  brought  to 
play  on  the  seam  until  fusion  occurs,  any 
reduction  in  the  thickness  of  the  metal  being 
made  good  by  fusing  a  stick  of  lead  at  the 
same  time.  Lead-burning  is  almost  exclu- 
sively used  for  joining  lead  in  chemical  works 
and  laboratories  where  acids  would  attack 
lead  solders — alloys  of  lead  and  tin  ;  it  is  also 
largely  employed  for  building  up  rain-water 
heads  and  spouting,  and  for  ornamental  lead- 
work.  A  special  apparatus  is  required,  which 
may  either  take  the  form  of  a  generator  in 
which  zinc  is  immersed  in  dilute  sulphuric  acid, 
the  hydrogen  gas  evolved  being  mixed  with 
atmospheric  air  under  a  slight  pressure  prior 
to  issuing  from  the  burner ;  or  compressed 
oxygen  in  steel  cylinders  may  be  used,  coal 
gas  being  mixed  with  the  same  before  reach- 
ing the  burner ;  this  method  has  the  advan- 
tage of  being  ready  for  immediate  use.  Where 
a  town's  supply  is  not  available,  coal  gas  may 
be  had  in  steel  cylinders. 

SOAKERS. —  For  rendering  watertight  the 
junction  of  walls,  dormers,  &c.,  with  roofs, 
several  methods  are  employed,  the  best 
arrangement  being  "soakers " ;  the  seare  pieces 
of  sheet  metal,  preferably  lead  or  copper,  bent 
at  right  angles  and  placed  between  the  slates 
or  tiles  to  turn  up  against  the  wall,  &c.,  as  the 
work  proceeds.  The  required  length  of  soakers 
for  either  slates  or  tiles  may  be  calculated  by 
adding  the  total  length  of  the  slate  or  tile  to 
the  lap  and  dividing  by  2,  any  additional 
length  required  for  nailing  or  other  fixing  to 


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FIG.  18. — Soakers  and  Step  Flashing. 


FIGS.  19  and  20.— Secret  Gutters. 


FIG.  21. 

Flashings  and  Condensation  Gutters 
to  Roof  Lights. 


FIG.  23.— Double  Welt. 


FIG.  22.— Gutter  and  Apron  Flashing  to  Skylight. 

330 


FIG.  24. — Side  of  Dormer,  showing  Welts. 


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be  afterwards  added;  thus  a  20-in.  slate  with 
a  3-in.  lap  requires  a  soaker  11^  in.  long, 
plus,  say,  1  in.  for  nailing.  Soakers  should 
turn  against  the  wall  to  a  height  of  3  in.  and 
lay  under  the  slates  not  less  than  4  in.,  pre- 
ferably half  the  width  of  the  slates  or  tiles. 
It  is  not  necessary  to  use  lead  soakers  of  a 
heavier  substance  than  4  Ibs.  lead,  owing  to 
tilting  of  the  slates.  Copper  may  be  used  of 
a  thinner  substance  than  lead,  say  26  B.W.G., 
which  makes  an  excellent  soaker. 

STEP  FLASHING. — The  upstand  of  soakers 
should  be  covered  with  a  hanging  or  cover 
flashing.  When  soakers  are  fixed  against 
brickwork  the  flashing  should  be  stepped  into 
the  joints  of  the  same.  It  is  not  necessary  to 
employ  apron  flashing  with  soakers. 

HIP  AND  VALLEY  SOAKERS. — For  mitred  hips 
soakers  should  be  used  to  prevent  leakage  at 
the  mitre.  The  length  may  be  determined  as 
before,  the  shape  being  found  by  bending  a 
piece  of  lead  over  the  hip  and  cutting  the  top 
and  bottom  parallel  with  the  horizontal  edges 
of  the  slating,  the  sides  being  cut  parallel  to 
the  sides  of  the  slates  or  tiles.  Valley  soakers 
are  employed  in  connection  with  mitred  valleys 
and  are  of  a  similar  shape  to  hip-soakers,  the 
length,  &c.,  being  determined  in  the  same 
manner. 

SECRET  GUTTERS. — Secret  gutters  are  fre- 
quently substituted  for  soakers,  and  are  con- 
structed by  forming  a  channel  at  the  roof 
junction  and  lining  the  same  with  lead.  The 
principal  point  in  favour  of  secret  gutters  is 
that  practically  the  whole  of  the  leadwork  and 
pointing  may  be  completed  before  the  tiling 
or  slating  is  commenced  ;  for  this  reason  they 
are  frequently  fixed  to  dormers,  chimneys,  &c. 
An  objection  to  secret  gutters  is  that  stoppage 
and  subsequent  overflowing  may  be  caused  by 
pieces  of  mortar,  slate,  leaves,  &c.,  finding 
their  way  into  the  gutter.  The  width  of  the 
gutter  should  be  about  3  in.,  and  from  1  in.  to 
2  in.  deep.  When  secret  gutters  are  fixed 
against  walls  the  upstand  should  be  deep 
enough  to  stand  up  6  in.  above  the  finished 
surface  of  the  roof  and  be  stepped  into  the 
joints  of  the  wall. 


ROOF  LIGHTS. — Roof  lights,  especially  when 
exposed  to  driving  rains,  frequently  leak  at 
the  sill,  owing  to  the  apron  flashing  being 
improperly  fixed  ;  such  apron  flashings  should 
always  be  fixed  before  the  sill  is  placed  in 
position,  the  best  method  being  to  lay  the  lead 
on  the  curb  and  afterwards  turn  the  same  up 
on  the  inside  of  the  sill.  Should  a  condensation 
gutter  be  required,  the  lead  may  be  left  of 
sufficient  width  for  the  purpose,  grooves  being 
cut  in  the  curb  at  intervals  and  the  lead 
dressed  into  the  same  to  form  channels  for 
the  escape  of  condensation ;  an  alternative 
arrangement  is  to  turn  the  apron  up  on  the 
front  of  the  curb  and  provide  a  separate  piece 
to  lay  on  the  curb  and  form  the  condensation 
gutter.  Skylights  are  frequently  found  to 
leak  by  water  passing  over  the  back  of  the 
curb  ;  for  this  reason  the  curb  of  skylights 
should  stand  vertical  and  not  at  right  angles 
with  the  pitch  of  roofs. 

DORMERS. — As  in  the  case  of  roof  lights,  the 
apron  flashing  should  be  fixed  before  the  sill 
and  be  finished  as  explained  therein.  When 
lead  is  used  for  the  cheeks  of  dormers,  care 
should  be  taken  that  it  is  well  supported  by 
turning  over  the  top,  and  that  the  pieces  are 
not  of  excessive  size.  Instead  of  using  large 
pieces  and  fixing  the  same  with  "  soldered 
dots,"  it  is  far  better  to  use  narrow  strips  of 
lead  about  15  in.  to  18  in.  wide,  joining  them 
by  vertical  welts  in  which  copper  tacks — pre- 
viously screwed  to  the  woodwork — are  folded. 
Such  an  arrangement  avoids  the  use  of  dots, 
and  gives  greater  freedom.  The  lead  to  the 
tops  of  dormers  should  turn  down  over  the 
sides  and  front,  and  preferably  slope  towards 
the  back.  The  best  method  of  fixing  the  turned- 
down  edges  of  the  lead  is  by  means  of  "  under 
tacks  "  or  "  welt  tacks" ;  copper  nailing  should 
on  no  account  be  resorted  to. 

GUTTERS  AND  FLATS. — It  is  important  that 
the  woodwork,  drips,  and  falls  be  properly 
arranged  in  order  to  insure  a  sound  and  last- 
ing roof  or  gutter.  As  previously  remarked, 
the  lengths  of  the  pieces  of  lead  should  if 
possible  approximate  to  7  ft.  or  under.  In 
placing  the  rolls  for  lead  flats  regard  should 


331 


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ENCYCLOPEDIA   OF 


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FIG.  24A. 
Dripping  Edge  to  Top  of  Dormer. 


FIG.  28. — Section  of  Drip  to  Lead  Gutter. 


FIG.  25A. 
Dripping  Edge  to  Top  of  Dormer. 


FIG.  25.— Nail  Welt. 


FIG.  26.—  Roll  to  Lead  Flat. 


FIG.  29. — "  Shute  "  Discharge  over  E.  W.  Head. 


FIG.  27.— Roll  Ends  to  Lead  Flat. 


FIG.  30. — Section  of  Roof  Cesspool  with  Overflow. 


332 


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MUNICIPAL   AND    SANITAEY   ENGINEERING. 


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be  had  to  the  width  of  the  sheets  of  lead  to 
be  used  or  waste  may  occur ;  the  width  of  the 
bays  should  be  arranged  to  enable  a  sheet  of 
lead  to  be  cut  down  the  centre  ;  with  a  standard 
(7  ft.)  ksheet  this  would  be  3  ft.  6  in.  and  the 
distance  between  the  rolls  should  be  2  ft.  8  in., 


FIG.  31. — "  Bird's  Mouth"  Outlet  to 
Cesspool. 

allowing  3  in.  for  "  undercloak  "  and  7  in.  for 
"  overcloak." 

EOOF,  CESSPOOLS,  AND  SHOOTS. — Where  pos- 
sible, the  best  arrangement  for  discharging 
the  water  from  lead-lined  gutters  is  to  allow 
the  gutter  to  pass  through  the  wall  and  dis- 
charge over  a  hopper  head,  forming  a  "  shoot." 
Where  the  foregoing  is  undesirable,  cesspools 


FIG.  32. — Lead  Cesspool  to  Asphalt  Flat. 

may  be  used ;  the  outlet  pipe  should  be  wiped 
in,  and  an  overflow — also  wiped  in — provided  ; 
care  should  be  taken  to  keep  the  overflow 
below  the  drips  discharging  into  the  cesspool. 
Lead  cesspools  are  frequently  provided  to 
asphalt  flats  and  gutters ;  by  their  use  a  sound 


connection  may  be  made   between  the  outlet 
pipe  and  asphalt. 

COVERING  STONE  CORNICES. — Stone  cornices, 
especially  when  of  large  dimensions,  are 
frequently  covered  with  lead.  To  allow  of 
movement  where  the  cornices  weather  out- 
wards it  is  best  to  turn  the  lead  up  on  the 
face  of  the  wall,  and  not  bed  the  same  as  the 
erection  of  the  wall  proceeds.  The  pieces  of 


FIG.  33. 


FIG.  34. 
Lead  Coverings  to  Stone  Cornices. 

lead  may  be  joined  by  welts,  raised  or  sunk. 
Where  cornices  weather  inwards,  a  channel  or 
gutter  is  formed  into  which  the  lead  is  dressed ; 
if  the  cornice  will  permit  of  shallow  drips 
being  formed  it  is  preferable,  as  it  permits  the 
lead  to  be  used  in  smaller  pieces  than  when 
drips  are  not  possible.  To  prevent  the  lead 
being  blown  up  soldered  dots  are  sometimes 
used ;  these,  however,  hold  the  lead  too  rigid, 


333 


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ENCYCLOPEDIA   OF 


POP 


resulting  in  a  fracture  around  the  edges  of 
the  dots ;  a  much  better  method  is  to  form  lead 
dots  similar  in  appearance  to  rivets,  or  to  run 
in  lead  "  under  tacks  "  and  turn  the  lead  under 
the  same  as  in  securing  the  edges  of  lead  on 
dormer  tops.  W.  F. 

Plumbism.  —  Another  name  for  "lead- 
poisoning  "  (sec  article  "  WATER  SUPPLY," 
action  of  water  upon  lead). 

Polarite  (see  "  INTERNATIONAL  PROCESS  OF 
SEWAGE  PURIFICATION  ")  is  the  commercial 
name  for  magnetic  spongy  carbon  which  is 
obtained  from  a  certain  kind  of  iron  found  in 
parts  of  South  Wales.  This  material  has  been 
tested  by  Sir  H.  Eoscoe,  F.R.S.,  who  has  stated 
that  the  "  porous  nature  of  the  oxide,  its  com- 
plete insolubility,  and  its  freedom  from  rusting, 
constitute  its  claim  to  be  considered  a  valuable 
filtering  material." 

Population,  Estimation  Of.— In  Great 
Britain  and  Ireland  a  census  enumeration 
of  the  population  is  undertaken  every  ten 
years,  and  it  is  therefore  only  once  every  ten 
years  that  we  have  the  exact  numbers  and 
ages  of  those  living  in  any  community. 
During  inter-censal  periods  the  population 
has  to  be  estimated,  and  there  are  several 
ways  of  effecting  this.  One  simple  method  of 
obtaining  a  close  approximate  estimation 
involves  an  enumeration  of  the  number  of 
inhabited  houses  in  the  district  (a  figure 
obtained  from  the  rate  books),  and  allot- 
ment to  each  such  house  of  the  average 
number  of  inhabitants  found  to  be  occupy- 
ing a  house  at  the  last  census.  The  average 
number  of  persons  per  inhabited  house  may 
vary  from  4' 5  to  9  according  to  the  size  of  the 
house  and  the  social  class  of  the  occupants ; 
according  to  the  census  of  1901  it  was  5'19  in 
England  and  Wales.  In  addition  to  the  number 
thus  calculated  one  individual  should  be 
allowed  for  each  empty  house,  in  order  to 
account  for  caretakers  and  their  families. 
Another  means  of  estimating  the  population 


is  by  the  birth-rate,  where  this  remains  fairly 
constant  for  a  series  of  years  ;  under  the  latter 
circumstance  and  when  applied  to  large  popu- 
lations the  computation  is  found  generally  to 
closely  approximate  to  the  truth.  By  this 
method  the  population  is  represented  by  the 
number  of  registered  births  in  the  year  multi- 
plied by  a  thousand  and  then  divided  by  the 
mean  birth-rate  for  the  previous  ten  years. 
The  practical  drawback  to  this  method  is  that 
the  population  of  the  current  year  cannot  be 
estimated,  inasmuch  as  the  data  for  the 
calculation  are  not  available  except  in  respect 
of  a  past  year.  On  the  whole  the  method  used 
by  the  Registrar-General  is  the  most  satis- 
factory and  serviceable.  It  involves  the  use 
of  logarithms  and  is  carried  out  as  follows  : — 
from  the  logarithm  of  the  population  according 
to  the  last  census  is  deducted  the  logarithm  of 
the  population  from  the  immediately  preceding 
census.  The  difference  will  indicate  the 
logarithm  corresponding  to  ten  years'  increase 
in  the  population.  A  tenth  of  this  figure  will 
represent  the  logarithm  of  one  year's  increase. 
Now  assuming  that  it  is  five  years  since  the 
last  census  was  taken  we  shall  then  have  to 
provide  for  five  years'  increase  in  the  popula- 
tion, together  with  an  extra  quarter  of  a  year's 
increase,  in  order  to  take  into  account  the  fact 
that  the  census  was  taken  at  the  end  of  the 
first  quarter  of  the  year  and  the  population  is 
always  estimated  to  the  middle  of  the  year. 
The  logarithm  of  one  year's  increase  is  there- 
fore multiplied  by  5^  and  the  result  represents 
the  logarithm  of  5  J  years'  increase ;  this,  added 
to  the  logarithm  of  the  population  by  the  last 
census,  gives  us  the  logarithm  of  the  population 
five  years  later,  and  the  number  corresponding 
to  this  logarithm  furnishes  the  calculated 
population.  This  method  assumes  that  the 
population  is  increasing  or  decreasing,  since 
the  last  census,  in  the  same  ratio  as  between 
the  last  two  censuses,  and  it  is  here  that  ;i 
fallacy  may  arise :  and  the  estimates  of  popu- 
lation so  obtained  often  present  a  considerable 
departure  from  the  actual  truth  when  fresh 
census  figures  become  available  for  comparison. 

H.  11.  J\. 


334 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


PRI 


Pneumatic  Sewage  Lifts.    (See  "  EJEC- 
TORS.") 

Precipitating  or  Settling  Tanks. — In 

any  system  of  sewage  treatment  the  first  stage 
towards  purification  is  the  removal  of  the 
grosser  solids  such  as  rags,  faeces,  orange 
peel,  sticks,  miscellaneous  small  articles 
thrown  down  the  drains,  and  road  silt,  sand, 
&c.  This  is  done  by  means  of  preliminary 
screening,  followed  by  precipitation  in  tanks 
either  with  or  without  the  use  of  chemical 
precipitants.  Such  tanks  are  constructed 
either  upon  the  "absolute  rest"  principle 
(see  "  ABSOLUTE  REST  PRECIPITATION  TANKS  ") 
or  upon  the  "  continuous  flow"  method.  The 
latter  is  the  plan  most  generally  adopted,  as  it 
economises  tank  capacity  and  fall  in  con- 
struction. The  sewage  should  not  pass 
through  the  tank  in  less  than  two  hours,  and 
suitable  chemicals  are  requisite  for  producing 
the  clearest  of  effluents.  For  purely  domestic 
sewages  such  tanks  may  be  provided  with  a 
number  of  submerged  cross- walls  carrying 
iron  screens,  and  these,  together  with  scum- 
plates,  remove  sufficient  of  the  suspended 
solids  preparatory  to  the  second  stage  of  the 
purification  process  without  entailing  the 
expense  of  chemical  precipitants.  It  may 
be  worked  either  intermittently  or  con- 
tinuously, and  should  be  cleaned  out  once 
every  three  days,  or  at  least  once  a  week.  If 
not  cleaned  frequently  the  deposited  sludge 
soon  ferments,  generates  gas,  and  foul  matter 
is  carried  to  the  surface  of  the  liquid,  which 
spoils  the  quality  of  the  effluent.  Taking 
the  maximum  sewage  flow  per  hour  at  8% 
of  the  daily  flow,  and  allowing  for  a  minimum 
of  2  hours'  stay  in  the  tank,  the  capacity  should 
be  16  %  of  the  total  sewage  to  be  dealt  with. 
To  meet  practical  working  conditions  this 
volume  should  be  multiplied  by  3,  which  would 
thus  bring  the  total  tank  capacity  up  to  say 
50  %.  This  should  be  divided  amongst  three 
or  more  independent  tanks,  so  that  whilst  one 
tank  was  empty  for  cleaning,  two  would  be 
available  for  the  ordinary  sewage  and  fluctua- 
tions in  storm  flow.  It  will  be  obvious  that  the 


division  of  the  tank  room  into  several  small 
tanks  will  be  more  serviceable  in  practice  than 
the  same  capacity  in  larger  units.  If  the 
tank  liquor  is  to  be  passed  on  to  filters 
formed  of  fine  grade  material,  the  period 
of  flow  through  the  tank  would  require 
to  be  increased  to  10  or  12  hours.  Pre- 
cipitation tanks  are  used  "  in  parallel "  or 
"in  series."  With  ordinary  sized  tanks  the 
minimum  rate  of  flow  is  obtained  by  the 
former  method.  Where  tanks  are  worked 
"  in  series,"  after  a  certain  percentage  of 
solids  has  settled  out,  no  great  advantage 
is  gained  by  passing  the  sewage  through 
another  tank  at  the  same  rate.  For  further 
deposition  of  solids  quiescent  settlement  is 
necessary.  For  various  special  forms  of 
settling  tanks,  see  articles  on  "  DORTMUND 
SETTLING  TANK,"  "  COSHAM  PRECIPITATING 
TANK,"  "!VE'S  TANK,"  "CANDY  SETTLING 
TANK,"  and  "  DUNDRUM  SETTLING  TANK." 

W.  H.  M. 


Precipitation    Tanks. 

DISPOSAL.") 


(See     "  SEWAGE 


Privies.  —  Frequently  made  use  of  for 
cottage  property  in  country  districts  in  the 
absence  of  water-closets  or  suitable  conditions 
for  earth  closets.  They  are  of  two  kinds : 
privies  proper,  intended  for  excrementitious 
matter  only,  and  privy-middens,  provided  for 
the  disposal  of  ashes  and  general  refuse  in 
addition  to  excreta.  In  the  former  the  excreta 
is  collected  in  a  pail  or  other  suitable  remov- 
able receptacle  which  by  the  Model  By-laws 
is  restricted  in  capacity  to  a  maximum 
of  2  cub.  ft.,  so  as  to  insure  frequent 
emptying.  The  privy  apartment  should  be 
provided  in  the  open  and  have  no  direct 
communication  with  the  dwelling-house.  The 
floor  must  be  of  non-absorbent  material  and 
at  least  6  in.  above  the  surrounding  ground, 
while  that  portion  under  the  seat  on  which 
the  pail  rests  must  not  be  less  than  3  in. 
above  the  ground.  The  apartment  should 
be  well  lighted  and  must  be  ventilated  by 
at  least  one  opening  communicating  directly 


335 


PUB 


ENCYCLOPAEDIA   OF 


PUM 


with  the  open  air  and  placed  as  near  as 
possible  to  the  roof.  The  walls  of  the  space 
enclosed  by  the  seat  must  be  impervious, 
and  the  pail  should  be  removable  from  the 
outside.  Privy-middens  are  usually  provided 
with  a  fixed  receptacle  or  non-absorbent  pit, 
which  by  the  Model  By-laws  is  limited  to  a 
capacity  of  8  cub.  ft.  to  ensure  at  least  weekly 
removal  of  its  contents.  This  pit  is  most 
conveniently  so  built  that  one-half  is  situated 
in  the  privy  apartment,  while  the  other  half 
projects  outside  the  building.  Over  the  former 
the  seat  is  fixed,  over  the  latter  half  a  flap  is 
provided  through  which  ashes  and  other  dry 
house  refuse  are  thrown  in.  That  this  should 
be  regularly  mingled  with  the  excreta  is 
important.  A  coarse  sieve  may  be  provided 
in  the  opening  for  the  purpose  of  screening 
the  ashes  from  the  cinders.  With  the  excep- 
tion of  the  receptacle,  the  construction  of  the 
privy  apartment  does  not  differ  from  that 
above  described. 


Public  Health. 

HEALTH.") 


(See  "  HYGIENE  AND  PUBLIC 


Pumps    and    Pumping   Machinery.— 

The  principle  of  the  action  of  the  pump,  like 
that  of  the  siphon  and  other  similar  hydraulic 
applications,  depends  upon  the  balance  of 
weight  between  a  column  of  water  of  a  cer- 
tain height  and  the  atmosphere.  The  best 
results  are  obtained  from  10  ft.  to  15  ft., 
and  with  high  speeds  the  shorter  the  suction 
the  greater  the  efficiency. 

The  different  classes  of  pumps  here  illus- 
trated are  the  common  suction  pump  (Fig.  1), 
the  lifting  pump  (Fig.  2),  the  single-acting 
piston  pump  (Fig.  3),  the  plunger  pump 
(Fig.  4),  the  horizontal  plunger  pump  with 
air  vessel  (Fig.  5),  the  double  acting  piston 
pump  (Fig.  6),  and  the  combined  plunger  and 
bucket  pump  (Fig.  7).  In  all  of  them  the 
suction  valve  must  be  within  the  usual  limit  of 
height  from  the  surface  of  the  water  to  be  raised, 
but  by  a  suitable  arrangement  of  valves  within 
the  barrel  of  the  pump  the  water  may  be  lifted 
to  any  desired  elevation.  Thus  in  Fig.  2  it 


will  be  observed  that  the  common  suction 
pump  is  converted  into  a  "  lifting  pump  "  by 
attaching  a  rising  pipe  in  the  place  of  the 
ordinary  spout  and  placing  a  valve  at  the 


\atues- 


Jacket  — 


Cylindrical 
Pump  Barrel 


Suction; 


Water  Level 

'Well 
FlG.  1. — Common  Suction  Pump. 

lower  end  of  this  pipe  to  prevent  the  return  of 
the  water.  As  this  modification  causes  con- 
siderable pressure  within  the  pump-barrel,  its 
upper  end  is  securely  covered  down  and  the 


Stuffing 
Sox 


Piston,  Rod- 

I"      1t 


JUsina 
'Pipe 


Valve 


FlG.  2.— Lifting  Pump. 

piston-rod  works  through  a  stuffing-box  as 
shown.  It  is  clear  that  each  rise  of  the  piston 
forces  some  portion  of  the  contents  of  the 
pump-barrel  upwards  into  the  rising-pipe,  also 


336 


PUM 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


PUM 


that  the  power  required  to  work  the  pump 
must  be  sufficient  not  only  to  fill  the  barrel 
from  below  but  also  to  lift  the  column  of  water 
in  the  rising-pipe.  The  retaining  valve  at  the 
foot  of  the  rising  pipe  is  not  necessary  to  the 
action  of  the  pump  because,  the  barrel  being 
full,  the  suction  valve  retains  the  water,  but  it 
is  employed  as  an  additional  check  and  relieves 
the  valves  below  it  of  excessive  pressure  and 
prevents  leakage. 

"  STUFFING-BOX." — An  enlarged  sectional 
view  of  a  "stuffing-box"  is  given  in  Fig.  8.  It 
may  be  described  as  a  device  for  rendering  a 
joint  impervious  where  there  is  a  hole  through 
which  a  movable  cylindrical  rod  or  plunger, 
such  as  the  piston  rod  of  a  steam  engine  or 


pump  barrel  need  not  be  covered  down.  A 
little  water  poured  in  at  the  top  of  the  barrel 
makes  the  piston  air-tight.  When  the  piston 
is  raised,  the  valve  at  the  foot  of  the  rising- 
pipe  closes  and  the  suction  valve  opens, 
admitting  water  from  below  into  the  barrel. 
Upon  the  return  of  the  piston  downwards,  the 
suction  valve  closes  and  the  retaining  valve 
(at  foot  of  rising-pipe)  opens  and  water  is 
forced  up  the  pipe. 

In  the  plunger  pump  (Fig.  4),  the  delivery 
is  on  the  down  stroke  as  in  the  case  of  the 
pump  last  described,  and  the  action  of  the 
valves  is  also  similar.  In  this  case,  however, 
a  solid  plunger  is  substituted  for  the  piston, 
whereby  the  expense  of  turning  the  cylinder 


FIG.  3. — Single- Acting  Piston  Pump. 

the  plunger  or  rod  of  a  pump,  slides  to  and 
fro,  and  which  requires  to  be  kept  water  or 
steam-tight  under  pressure.  Generally,  ifc 
consists  of  a  box  or  chamber,  made  by  an 
enlargement  of  part  of  the  hole,  thus  forming 
a  space  around  the  piston  rod  for  containing 
packing  which  is  pressed  home  and  made  to 
tightly  fill  the  space  by  means  of  a  sleeve, 
called  a  "  gland,"  fitting  loosely  around  the 
rod,  and  pressed  down  upon  the  packing  by 
tightening  the  bolts  shown  in  the  illustration 
attaching  the  gland  to  the  box. 

The  single  acting  piston  pump  (Fig.  3)  is 
used  to  force  water  up  to  any  required  height. 
It  differs  from  the  lifting  pump  in  that  the 
piston  contains  no  valve  and  the  top  of  the 


Ftvatgei- 

Gland  and 
StvffingBcx 

barrel- 


Rising 
'Main, 


-TJeliverj? 
Value 


Suction, 


FIG.  4. — Plunger  Pump. 

true  is  avoided,  and  the  plunger  also  better 
resists  the  wear  from  grit,  &c.,  within  the  pump 
barrel.  The  top  of  the  barrel  must,  however, 
be  tight,  and  the  plunger  therefore  works 
through  a  gland  and  stuffing-box.  At  each 
stroke  this  pump  raises  a  volume  of  water 
equal  to  that  of  the  plunger. 

A  plunger  pump  with  air  vessel  attached  is 
shown  in  Fig.  5.  The  object  of  this  is  to 
make  the  working  of  the  pump  smoother  and 
the  flow  of  the  water  more  uniform.  The  air 
vessel  is  attached  at  the  foot  of  the  delivery 
pipe,  and,  during  the  inward  stroke  of  the 
plunger,  part  of  the  water  leaving  the  pump- 
barrel  passes  into  the  delivery  pipe  and  a 


M.S.E. 


337 


PUM 


ENCYCLOPAEDIA  OF 


PUM 


portion  into  the  air  vessel  and  compresses  the 
.air  contained  in  its  upper  end.  On  the  out- 
ward stroke  the  air  thus  imprisoned  and  com- 
pressed exerts  a  force  upon  the  water  and 
forces  it  out  into  the  delivery  pipe,  thus  main- 


Air  Vessel 
Delivery  Valve- 


Plu-Tiger 


Gland  and 
Stuffing  Sox 

Suctiorv  Pipe 


FIG.  5. — Plunger  Pump  with.  Air  Vessel. 

taining  a  more  uniform  flow,  and  acting  as  a 
sort  of  cushion  to  absorb  the  otherwise  marked 
effect  of  each  stroke  of  the  plunger.  An  air 
vessel  also  economises  the  power  employed  to 
work  the  pump  as  it  imparts  to  the  water  a 
constant  forward  motion. 

In  the  double-acting  piston  pump  (Fig.  6) 
there  are  two  suction  valves  and  two  delivery 


t 
Delivery^ 


^Piston  Rod 
Stuffing  Box. 


Delivery 
Valve 


— Piston, 


Suction, 


Suction, 


t 


FIG.  6.— Double-Acting  Piston  Pump. 

valves  placed  as  shown  in  the  figure,  all  open- 
ing to  the  left.  Water  is  delivered  upon  both 
the  up  and  down  strokes.  On  the  up  stroke, 
water  enters  the  pump  barrel  through  the 
suction  valve  D,  and  passes  into  the  rising-pipe 
through  valve  A .  On  the  down  stroke,  water 


is  forced  through  valve  C,  and  enters  above  the 
piston  at  valve  B,  thus  maintaining  a  constant 
discharge. 

The  double-acting  pump  shown  in  Fig.  7 
is  a  combination  of  a  plunger  pump  discharg- 
ing water  on  the  inward  stroke  and  a  bucket 


Gland- 


-Valve 
-Valve 


pIG.  7. — Combined  Plunger  and 
Bucket  Pump. 

pump  discharging  on  the  outward  stroke,  thus 
giving  a  continuous  flow.  The  area  of  the 
cross-section  of  the  plunger  is  made  half  that 
of  the  pump  barrel,  so  that  on  the  up  stroke 
half  the  water  raised  by  the  bucket  goes  to  fill 
the  space  left  by  the  plunger  and  the  other 


— Piston,  rod 
Gland 


Head,  of  pump  barrel 
(or  of  steam,  engine 
cylinder) 

FIG.  8.—"  Stuffiug-Box." 

half  is  passed  up  the  rising-pipe.  On  the 
down  stroke  the  plunger  displaces  half  of  the 
water  raised  by  the  bucket  and  forces  it  into 
the  delivery  pipe.  This  form  of  pump  \\as 
invented  by  Perkins,  introduced  at  the 
Lambeth  Waterworks  in  1848,  and  is  exten- 
sively used  in  most  of  the  large  waterworks. 


338 


PUM 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


PUM 


The  working  barrels,  buckets,  and  valves  of 
pumps  should  be  made  of  brass,  gunnietal,  or 
phosphor-bronze,  as,  though  initially  costly, 
these  metals  will  be  found  to  be  more  durable 
and  give  greater  satisfaction  in  working.  They 
are  not  liable  to  corrosion  by  the  action  of  the 
water,  will  be  found  more  accurate  in  their 
operation  than  iron,  and  are  less  liable  to 
injure  the  leather  attached  to  the  bucket  and 
valve,  which  are  parts  frequently  requiring 
attention  and  repair.  In  force  pumps  the 


FIG.  9. — Clack  Valve. 

packing  of  the  piston  or  box  is  an  important 
matter,  and  is  usually  made  of  waste  tow 
soaked  in  tallow  and  rammed  tight,  or,  where 
there  is  great  pressure,  cup  leather  packings 
are  employed.  In  the  close-topped  pumps 
working  through  a  stuffing-box  the  rising- 
pipe  and  suction  are  frequently  made  about 
two-thirds  the  area  of  the  working  barrel.  In 
the  case  of  quick-running  pumps  the  diameter 
of  the  suction  should  not  be  less  than  that  of 
the  working  barrel,  and  every  means  should 


FIG.  10.— Conical  Valve. 

be  adopted  to  enable  the  water  to  reach  the 
pump  very  readily. 

The  force  required  to  work  a  pump,  or  the 
pull  on  the  pump  rod,  is  equal  to  the  weight 
of  a  column  of  water  having  a  base  equal  in 
area  to  that  of  the  bucket  or  plunger,  and  a 
height  equal  to  the  height  to  which  the  water 
is  being  raised. 

For  hand  pumping  from  ordinary  wells 
under  30  ft.  in  depth,  a  convenient  size  of 


pump  for  one  man  to  work  is  a  4  in.  working 
barrel  with  a  9-in.  or  10-in.  stroke.  This 
pump  will  throw  24  gallons  per  minute  from  a 
20-ft.  well.  Between  the  depths  of  30  ft. 
and  70  ft.  a  3J  in.  diameter  working  barrel 
with  a  9-in.  or  10-in.  stroke  maybe  employed, 
but  for  wells  over  70  ft.  a  strong  three-throw 
pump  consisting  of  three  working  barrels 
standing  side  by  side  upon  a  horizontal  valve- 
box  common  to  the  three  barrels,  and  worked 
from  the  top  by  means  of  pump-rods  actuated 


PlG.  11. — Flap  or  Hinged  Valve. 

by  a  three-throw  crank,  wheel  and  pinion, 
driven  by  either  horse-gearing  or  steam  oil  or 
gas  power,  will  be  found  the  most  suitable 
type. 

PUMP  VALVES. — Pumps  are  placed  between 
the  water  to  be  raised  and  the  point  of  delivery, 
and  have,  therefore,  to  perform  two  distinct 
operations,  viz.,  to  suck  or  draw  the  water  into 
the  pumps,  and  then  to  force  it  to  the  required 
elevation.  Valves  are  therefore  a  necessity 
for  the  control  of  the  water  so  raised,  their 
function  being  to  open  freely  to  the  forward 


FIG.  12.— Conical  Disc  Valve. 

motion  of  the  water  and  to  close  against  its 
return,  and  so  prevent  loss  of  the  work  done 
by  the  pump,  piston,  or  plunger  in  giving  the 
water  its  forward  motion.  The  valves  of  every 
pump  thus  form  a  most  important  part  of  the 
apparatus  and  require  careful  attention  in 
their  design  and  maintenance,  otherwise  a 
large  proportion  of  the  power  expended  in 
pumping  will  be  lost  through  excessive  friction 
or  "  slip,"  and  the  cost  of  pumping  per  1,000 


339 


z2 


PUM 


ENCYCLOPEDIA   OF 


PUM 


gallons  raised  will  become  excessive.  To  pre- 
vent slip  the  valves  should  offer  little  resistance 
to  the  passage  of  the  water  in  one  direction 
and  close  quickly  and  tightly  in  the  opposite 
direction,  but  without  shock.  The  construc- 
tion of  the  valves  of  a  pump  largely  determines 
the  speed  at  which  it  may  be  worked.  For 
fast  working  low  lifts  are  necessary.  The 
weight  of  a  valve  should  be  sufficient  to  close 
without  knocking,  and  should  at  the  same 


r 

-Perforated  guard 
'India-rubber  disc, 

Open  grating 


^Cross-bar 
FIG.  13. — India-rubber  Disc  Valve. 

time  be  light  enough  to  be  lifted  without  great 
resistance  to  the  water.  In  the  case  of  high 
lifts  the  weight  of  the  valve  is  very  generally 
estimated  at  1  Ib.  per  square  inch  of  area, 
equal  to  a  head  of  about  2^  ft.  of  water, 
whilst  for  low  lifts  it  may  be  from  \  Ib.  to  J  Ib. 
per  square  inch  of  area.  A  small  lift  in  a 
valve  is  desirable,  as  it  enables  the  valve  to 
close  quickly,  thus  reducing  shock  as  well  as 
slip.  The  velocity  of  the  water  through  a 


Metal  jdate 


FIG.  14.— Butterfly  Valve. 

valve  should  not  exceed  about  5  ft.  per 
second,  and  in  a  well-made  pump  the  slip 
should  not  exceed  from  5  to  7  %.  Valves 
of  the  "  butterfly  "  type  allow  more  slip  than 
"  double-beat "  valves. 

Various  classes  of  valves  are  shown  in 
Figs.  9  to  16 ;  generally  speaking,  they  may 
be  divided  into  two  classes,  viz.,  hinged  or 
door  valves,  and  spindle  valves.  The  ordinary 
"  clack  "  valve  and  "  conical  "  valve  as  used  in 


the  common  suction  pump  are  shown  in 
Figs.  9  and  10.  The  flap  or  hinged  valve 
consists  of  a  flap  of  stout  leather  stiffened 
with  metal  plates  and  working  on  a  hinge. 
Fig.  12  shows  a  conical  metal  disc  valve  work- 
ing on  a  central  spindle.  The  conical  edge 


FlG.  15. — Mitre  Valve. 

fits  accurately  upon  a  corresponding  seating 
sloped  at  an  angle  of  45°  with  the  valve 
axis.  The  lift  of  the  valve  is  limited  by  a  stop 
placed  above  it,  and  the  amount  of  the  rise 
should  not  exceed  one-fourth  of  the  diameter 
of  the  valve.  An  india-rubber  disc  valve  is 
given  in  Fig.  13 ;  it  consists  of  an  open 


-^-Lift  of  valve 


Beat 


FIG.  16. — Double-Beat  Valve. 

grating  covered  with  a  disc  of  india-rubber 
surmounted  by  a  perforated  guard,  against 
which  the  force  of  the  passing  water  raises  the 
india-rubber.  On  the  return  of  the  water 
pressure  downwards  the  india-rubber  is  forced 
back  tightly  upon  its  seating.  The  apertures 
in  the  grating  are  made  at  an  angle,  thus 
producing  a  circular  motion  in  the  valve  as 


840 


PUM 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


PUM 


the  water  passes  through,  which  prevents  the 
valve  falling  in  the  same  position  and  cutting 
the  rubber.  Strong  dark-blue  rubber  is  used 
for  heavy  work.  The  "  butterfly  "  valve 
(Fig.  14)  is  formed  of  semi-circular  discs 
hinged  at  the  centre  as  shown,  and  is  made  of 
leather  and  metal  plates  similar  to  the  hinged 
valve.  The  mitre  valve  (Fig.  15)  consists  of 
a  circular  metallic  disc  with  conical  face. 
The  short  stop  above  the  valve  limits  its  lift, 
and  feathers  below  guide  the  valve  on  to  its 
seat.  The  "double-beat"  valve  (Fig.  16)  is 
an  extensively  used  form  of  valve,  and  was 
designed  to  overcome  the  great  wear  and  tear 
of  the  flap  valves.  It  consists  of  two  circular 
rings  on  which  the  upper  and  lower  parts  of 
the  valve  respectively  beat,  thus  forming  the 
"double  beat,"  as  illustrated.  The  beats  are 
of  lignum-vitae,  leather,  or  white  metal,  and 
are  fixed  to  the  valve  and  beat  on  a  gun-metal 
seat.  Owing  to  the  two  openings  for  discharge, 
this  valve  has  the  advantage  of  a  small  lift, 
and  the  shock  caused  by  closing  is  thus 
reduced  in  consequence.  The  webs  connecting 
the  parts  together,  being  made  at  a  slight 
angle,  cause  the  valve  to  rotate  during  the 
passage  of  water,  which  tends  to  keep  the 
beats  perfect  and  to  prevent  grooving.  In  the 
double-beat  valve  adapted  for  heavy  lifts  the 
bottom  beats  are  usually  of  gun-metal  and  the 
upper  ones  may  be  of  hippopotamus  hide  or 
similar  leather. 

More  complicated  valves  than  the  foregoing 
are  also  used,  such  as  three-  and  four-beat 
valves,  made  011  the  same  principle  as  those 
referred  to  above,  and  taking  their  names 
according  to  the  number  of  the  beats. 

The  Eiedler  valve  has  been  largely  used  on 
the  Continent  with  much  satisfaction,  and  has 
also  been  employed  in  four  compound  pump- 
ing engines  supplied  to  the  Grand  Junction 
Water  Co.'s  works  at  Hampton.  In  ordinary 
pumping  engines  of  this  class  it  is  difficult  to 
run  fast  owing  to  the  concussion  and  vibration 
occasioned  by  the  sudden  closing  of  the  pump 
valves  at  the  end  of  each  stroke.  In  the 
Eiedler  engines  the  pump  valves  are  mechanic- 
ally closed  much  in  the  same  way  as  the  valves 


of  a  steam-engine,  and   by  these  means  the 
difficulty  of  fast  running  is  overcome. 

In  the  design  of  pump  valves  it  should  be 
borne  in  mind  that  all  types  break  up  and 
impede  the  advancing  water  column  to  some 
extent  in  passing  through  the  pumps,  and 
that  in  this  way  friction  is  caused  and  a 
certain  proportion  of  power  of  the  engines  is 
consumed.  The  object  to  be  aimed  at,  there- 
fore, is  to  reduce  these  losses  to  a  minimum  by 
avoiding  unnecessary  division  or  deflection  of 
the  water  by  the  valves  and  short  bends  or 
contractions  in  the  water  passages.  Formerly, 
the  increase  of  the  sizes  of  valves  in  the 
building  of  large  pumping  engines  gave  rise 
to  considerable  shock  and  vibration  upon  the 
valves  coming  upon  their  seatings,  the  impact 
of  which  often  made  the  whole  machinery  and 
buildings  shake.  This  difficulty  led  to  the 
practice  of  dividing  the  valves  into  nests  of  the 
double-beat  form,  and  in  many  large  works  the 
valves  are  of  the  four-beat  class,  or  Husband's 
model.  The  valves  of  some  pumps  are  also 
divided  into  nests  of  a  dozen  or  more  of 
the  rubber-disc  type  as  above  described, 
and  by  this  means  the  shock  of  the  water- 
hammer  produced  when  the  valve  falls 
on  its  seat  is  reduced,  but  each  sub-division 
increases  the  frictional  resistance  to  the  flow. 
Pumps  of  the  "  Worthington  "  type  and  many 
modern  steam  fire-engines  are  fitted  with  nests 
of  rubber-disc  valves,  this  class  being  largely 
used  where  the  motion  is  rapid  and  the  pressure 
great. 

For  general  waterworks  use  valves  of  the 
"  Cornish  "  class  are  in  great  favour,  but  the 
more  complicated  modifications  of  this  type 
sometimes  give  trouble  from  noise,  vibration, 
sticking,  and  undue  friction.  For  metal  valves 
flat  faces  are  as  a  rule  better  than  conical 
faces,  especially  if  the  water  is  gritty.  Sharp 
angles  or  bends  should  be  avoided  and  all 
connections  made  with  easy  curves.  Where 
bends  are  unavoidable  air  cocks  should  be 
provided  for  the  escape  of  the  air  and  to 
insure  good  circulation  of  the  water.  Clack 
valves  are  sometimes  used  for  low  lifts  on 
small  pumps  where  the  water  contains  much 


341 


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ENCYCLOPEDIA  OF 


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sand,  and  when  this  class  of  valve  is  used  for 
larger  pumps  a  small  valve  is  provided  on  the 
top  of  the  large  one  to  reduce  the  shock,  as 
the  small  valve,  on  account  of  its  smaller  area, 
closes  and  opens  first,  and  so  relieves  the 
impact  of  the  water. 

MISCELLANEOUS  TYPES  OF  PUMPS. — In  addi- 
tion to  the  classes  of  pumps  already  referred 
to,  there  are  several  kinds  largely  employed 
for  various  purposes,  e.f/.,  the  centrifugal,  the 
pulsometer,  horehole  pumps,  the  semi-rotary, 
and  the  high  lift  turhine  pump. 

CENTRIFUGAL  PUMPS  are  much  used  where 
large  quantities  of  water  have  to  be  raised 
through  low  lifts,  such  as  for  the  drainage  of 
low-lying  land,  as  in  the  fen  districts,  emptying 
docks  and  reservoirs,  raising  large  quantities 
of  storm-water,  pumping  on  to  filter  beds,  and 
other  like  purposes.  Centrifugal  pumps  are 
driven  at  a  rapid  speed  by  means  of  good  wide 
belts  from  shafting,  or  by  a  steam-engine 
combined  direct  with  the  pump.  Having  no 
valves,  the  centrifugal  pump  lends  itself  well 
for  the  pumping  of  sewage  or  other  liquids 
carrying  a  large  proportion  of  solid  matter  in 
suspension,  but  it  is  desirable  to  exclude  such 
matters  as  pieces  of  yarn,  rope,  cloth,  &c.,  by 
means  of  a  coarse  screen  or  grid  on  the 
suction.  The  duty  of  the  centrifugal  pump 
below  20  ft.  lift  compares  favourably  with 
any  other  class  of  pump,  but  above  that  height 
the  efficiency  falls  off.  A  maximum  efficiency 
of  about  70  °/Q  is  reached  at  from  15  ft.  to  20  ft. 
lift.  The  speed  of  the  water  should  not  exceed 
about  8  ft.  per  second,  and  sudden  changes  in 
its  path  through  the  pump  should  be  avoided 
as  far  as  possible. 

THE  PULSOMETER  PUMP  is  an  indispensable 
appliance  for  contractors'  use  upon  engineering 
works  where  large  quantities  of  dirty  water 
may  have  to  be  removed.  It  is  easily  and 
quickly  suspended  in  almost  any  position,  and 
is  operated  by  the  admission  of  steam  from 
the  top  past  the  steam  ball  valve.  This 
presses  upon  the  surface  of  the  water  con- 
tained in  the  body  of  the  pump,  thus  depressing 
it  and  driving  it  through  the  discharge  outlet 
into  the  rising  main.  The  steam  pressure  at 


the  pump  should  not  be  less  than  from  20  Ibs. 
to  30  Ibs.  per  square  inch  for  lifts  from  20  ft. 
to  40  ft.,  and  from  30  Ibs.  to  50  Ibs.  for  lifts 
between  40  ft.  and  80  ft. 

BOREHOLE  PUMPS  are  fitted  in  a  working 
barrel  inside  the  steel  lining  of  the  well  and 
placed  at  a  sufficient  depth  to  insure  a  good 
draught  of  water.  The  pumps  are  commonly 
worked  from  a  bell-crank  in  the  engine-room 
by  means  of  iron  guides  steadied  by  guides 
working  against  the  lining  of  the  well.  Such 
pumps  should  be  drawn  for  inspection  and 
overhauling  at  periodic  intervals,  as  the  wear 
and  tear  is  often  considerable. 

THE  SEMI-ROTARY  WING  PUMPS  of  the 
"AVillcox"  type  are  very  useful  for  temporary 
purposes,  and  have  a  high  capacity  compared 
with  the  small  power  required.  The  pumps 
suck  vertically  a  height  of  25  ft.  with  the  use 
of  a  suction  or  foot  valve,  and  will  deliver  to  a 
vertical  height  of  about  110  ft. 

PISTON  OR  PLUNGER  SPEED  OF  PUMPS. — The 
possible  speed  of  the  plunger  depends  upon 
the  proper  filling  of  the  pump  during  each 
single  stroke.  The  readiness  with  which  such 
filling  takes  place  depends  greatly  upon  the 
size  and  design  of  the  suction  valves,  and  upon 
the  length  of  the  stroke. 

The  length  of  suction,  suitable  plunger 
speed  and  length  of  stroke,  and  the  good 
design  of  the  pump  valves,  are  first  essentials 
to  the  smooth  and  satisfactory  working  of 
pumps,  freedom  from  "  knocking,"  and  other 
troubles. 

It  is  impossible  to  lay  down  any  fixed  rule 
as  to  the  plunger  speed  of  a  pump,  since  this 
will  vary  with  the  different  conditions  to  be 
met. 

Usually  the  longer  the  stroke,  and  the 
greater  the  ease  with  which  the  water  reaches 
the  pump,  the  greater  the  piston  speed  per- 
missible. A  high  piston  speed  in  an  engine 
tends  to  economical  working,  as  the  cylinders, 
having  less  time  during  which  to  become 
cooled  between  the  successive  admissions  of 
fresh  steam,  give  less  loss  from  initial  con- 
densation. In  order  to  secure  the  advantage 
of  a  high  steam-piston  speed  with  a  low 


342 


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MUNICIPAL   AND    SANITAEY  ENGINEEEING. 


PUM 


pump-plunger  speed,  gearing  is  frequently 
resorted  to,  but  usually  with  some  unavoid- 
able sacrifice  of  mechanical  efficiency.  The 
mean  piston  speed  of  an  engine  is  ascertained 
by  multiplying  twice  the  stroke  in  feet  by  the 
number  of  revolutions  per  minute.  Thus,  an 
engine  having  a  40-in.  stroke  and  making  28 
double-strokes  per  minute,  has  a  piston  speed 
of  153'4  ft.  per  minute.  Vertical  direct-acting 
pumping  engines  usually  run  at  from  20  to  25 
revolutions  per  minute. 

Pounding  in  pumps  is  a  common  trouble 
and  may  arise  from  too  sudden  closing  of  the 
valves,  through  the  valves  having  too  great  a 
lift,  or  from  other  defects  in  the  water  cylinder. 
Want  of  lead  in  the  steam  valve,  insufficient 
clearance,  defective  piston  rings,  and  worn 
bearings  may  also  produce  the  pounding 
effect.  Too  heavy  a  duty  for  the  pumps  is 
another  cause. 

Packings  to  piston  rods  of  steam  cylinder 
and  to  pump  pistons  is  a  practical  detail  of 
much  importance.  Neglect  on  this  point  may 
lead  to  serious  scoring  or  grooving  of  the 
piston  rod,  to  undue  friction  on  the  rod 
causing  waste  of  power,  to  leakage  of  steam, 
and  other  defects.  Some  of  the  materials 
which  have  been  used  for  steam  cylinders  are 
asbestos,  spun  yarn,  hemp,  French  chalk, 
metallic  packing,  and  ordinary  cotton  rope 
with  a  French  chalk  core.  With  all  packings 
the  stuffing-box  should  not  be  over-tilled,  and 
the  gland  should  be  screwed  up  evenly  all  round. 

For  the  packing  of  pump  pistons  leather  of 
the  best  quality,  layers  of  cotton  and  rubber, 
and  metallic  rings  of  cast  iron,  steel,  and  gun- 
metal  are  used.  Springs  are  employed  to 
expand  some  of  the  metallic  packings,  but 
these  require  careful  adjustment  or  an  uneven 
and  unnecessary  frictional  loss  may  be  caused. 
For  large  pumps  plaited  hemp  makes  a  good 
packing,  and  for  small  pumps  ordinary  gasket 
is  used  when  well  greased  with  tallow. 

SELECTION  OF  PUMPING  MACHINERY. — In  the 
great  majority  of  waterworks  the  provision 
of  the  most  suitable  and  efficient  class  of 
pumping  machinery  forms  a  leading  factor 
in  their  proper  equipment  and  design. 


Great  variety  exists  in  the  class  and  arrange- 
ment of  machinery  which  may  be  employed, 
and  in  practice  each  case  will  require  to  be 
separately  considered  in  the  light  of  the 
special  circumstances  to  be  met.  The  engi- 
neer must  take  into  account  the  question  of 
the  most  suitable  type  of  machinery  for  the 
case  in  point,  the  capital  cost  of  the  engine, 
pumps,  boilers,  buildings,  foundations,  and 
other  accessory  works  ;  and  also  the  probable 
annual  working  expenses  which  will  be  incurred 
in  wages,  fuel,  repairs,  and  other  charges. 
The  class  of  motive  power  to  be  adopted  and 
the  convenience  for  the  delivery  of  fuel  to  the 
site  should  also  largely  influence  the  decision. 

It  is  usually  advisable  to  Carefully  compare 
the  cost  of  alternative  proposals,  and  for  this 
purpose  the  various  items  of  yearly  expendi- 
ture should  be  capitalised  and  added  to  the 
initial  cost  of  the  buildings  and  plant  involved 
by  each  alternative  proposal,  so  that  a 
comparison  upon  an  equal  basis  may  be 
made. 

In  motive  power  the  various  alternatives 
lie  mainly  between  steam,  gas,  oil,  and  elec- 
tricity— the  final  choice  depending  largely 
upon  the  size  of  the  water  undertaking,  the 
relative  prices  of  coal,  gas,  or  oil  delivered  to 
the  site,  and  other  special  facilities  which  may 
operate  in  favour  of  any  one  of  these  agents 
named  in  preference  to  others. 

Where  there  is  a  large  amount  of  pumping 
to  be  done,  high  pressure  steam  used  expan- 
sively will  usually  be  found  to  be  by  far  the 
most  economical  and  reliable  motive  power ; 
but  in  the  case  of  small  rural  works,  or  at 
small  isolated  stations  of  larger  undertakings, 
gas  and  oil  engines  will  frequently  be  found 
the  most  serviceable  and  convenient  agents 
to  employ.  The  latter  will  also  be  found 
advantageous  in  cases  where  the  pumping  is 
intermittent  and  continued  for  short  periods 
only  according  to  requirements. 

In  every  pumping  works  it  is  necessary  to 
have  a  certain  proportion  of  "stand-by"  plant 
in  order  that  the  regular  supply  to  the  town 
may  not  be  interrupted  in  the  event  of  a 
temporary  break- down  of  an  engine  or  any 


343 


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ENCYCLOPEDIA   OF 


RAI 


part  of  the  machinery.  In  small  works  it  is 
customary  to  have  the  pumping  plant  in 
duplicate,  but  in  large  stations  this  is  not 
necessary  as  here  the  pumping  power  is 
usually  made  up  of  a  number  of  pumping 
units,  the  break-down  of  any  one  of  which 
will,  as  a  rule,  not  seriously  incommode  the 
supply.  In  such  a  works  the  stand-by  plant 
need  not  be  more  than  one-third,  one-fourth, 
or  even  one-fifth  of  the  whole,  according  to 
the  size  of  the  works,  the  power  of  the 
pumping  units  employed,  and  the  amount  of 
high  level  storage  between  the  pumps  and  the 
water  consumer. 

Another  important  question  affecting  the 
amount  and  arrangement  of  pumping  power 
and  the  quantity  of  stand-by  plant  required 
is  the  system  upon  which  the  supply  is 
delivered  into  the  town.  Where  the  water 
is  pumped- direct  into  the  mains,  the  pumps 
must  be  fully  equal  to  the  maximum  rate  of 
supply  and  must  closely  follow  the  fluctuations 
of  demand  during  the  different  periods  of  the 
24  hours.  There  must  be  ample  stand-by 
plant,  and  the  whole  pumping  arrangements 
and  staff  must  be  ready  to  meet  any  emergency 
promptly,  whether  it  be  from  break-downs, 
excessive  consumption  through  drought,  leak- 
age, fire,  or  other  causes.  A  more  satisfactory 
mode  of  supply,  and  one  entailing  less  anxiety 
at  the  pumping  station,  is  that  in  which  the 
engines  deliver  into  a  high-level  storage 
reservoir  containing  a  day  or  two's  con- 
sumption, or  oftentimes  much  less,  upon 
which  the  town  may  draw  during  a  temporary 
cessation  of  pumping.  Again,  where  there  is 
no  such  reservoir,  the  fluctuations  of  con- 
sumption are  balanced  for  brief  periods  in 
some  cases  by  the  use  of  stand-pipes  and 
water-towers.  W.  H.  M. 


Purification 

TION.") 


of  Water.    (See   "  FILTRA- 


Rain- water  Cistern,  Venetian. — Rain- 
water reservoirs  are  the  chief  sources  of  water 
bupply  along  extensive  tracts  of  the  Italian 
coast.  In  most  parts  of  the  country  the 
reservoirs,  like  those  of  the  East,  are  entirely 


or  partly  sunk  in  the  ground  and  covered  over, 
the  rain  from  roofs  passing  through  strainers 
before  entering  the  cistern.      The   Venetian 
type  is  an  improvement  on  the  above.     The 
cistern  is  divided  into  two  equal  sections  by 
means   of   a   partition   descending   from   the 
domed  or  flat  roof  to  within  a  few  inches  of 
the  bottom.     Both  sections  are  half  filled  with 
filtering  materials,  generally  consisting  of  three 
layers  of  equal  thickness — sand  being  at  the 
base,  protected  by  a  layer  of  fine  gravel,  with 
coarse    gravel    on    the   top.      Rain    passing 
through  strainers  enters  one  section  of  the 
cistern,  and  passing  downwards  through  the 
filtering  material  makes  its  way  through  the 
slit  at  the  base  of  the  partition  into  the  second 
division  rising  through  the  filtering  materials. 
The  water  is  raised  from  this  section  either 
by  means  of  buckets,  an  opening  in  the  roof, 
generally   arched   over   to   afford   protection, 
being  provided ;  or,  better  still,  by  means  of 
a  pump.     A  sealed  manhole  should  be  placed 
in  the  roof  of  each  section.     In  this  country, 
where    the    air   is    apt    to   be    contaminated 
with  dust  and  soot,  it  is  advisable  to  use  a 
"  rainwater  separator  "  (q.  r.)  in  place  of  an 
ordinary  strainer.     Rainwater  from  a  cistern 
built  on   the   above   principle   by  Dr.  Poore 
at    Andover   was    analysed    chemically   and 
bacterioscopically  by  the  Royal  Commission 
on  Sewage  Disposal  in  1901,  with  the  following 
result : — 

PAKTS  PER  100,000  BY  WEIGHT. 
Ammoniacal  nitrogen   ....  0*004 
Albuminoid         „          ....  0'020 

Nitrite 0'033 

Nitrate 0'086 

Oxygen  absorbed  from     )  at  once          .  0'23 

permanganate  at  80°  F. )  after  4  hours  0'48 

After  incubation  at  80° F.)  at  once          .  0'23 

for  6  days  j  after  4  hours  0'79 

Combined  chlorine        ....  0*16 

Dissolved  oxygen  (parts  per  1,000  by 

volume) 2'8 

25  bacteria  per  c.c.  were  found  on  gelatine 
at  20°  C.,  and  7  per  c.c.  on  agar-agar  at  37°  C. 
Tests  for  bacillus  coli  and  b.  e)it<'ri<litis 
sporogenes  gave  negative  results. 


344 


RAI 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


REF 


Rain-Gauge. — This  is  an  instrument  for 
measuring  the  rainfall.  It  is  best  made  of 
copper,  and  should  have  a  circular  funnel  of 
5  or  8  in.  diameter.  It  should  be  of  the 
Snowdon  pattern — that  is,  have  a  deep  rim  to 
retain  snow — and  should  be  placed  with  its 
rim  1  ft.  above  the  ground,  in  an  open  and 
well-exposed  situation.  The  measurement  of 
the  rain  is  affected  by  pouring  out  the  contents 
of  the  can  or  bottle  into  the  glass  measure, 
and  reading  off  to  hundredths  of  an  inch. 
The  gauge  should  be  examined  daily  at  9  A.M., 
and  the  rainfall,  if  any,  entered  to  the  previous 
day.  When  snow  falls,  that  which  is  collected 
in  the  funnel  should  be  melted  and  measured 
as  rain.  By  an  inch  of  rain  is  meant  the 
height  to  which  the  water  would  stand  on  the 
level,  provided  it  did  not  run  off,  or  soak  into 
the  ground,  or  evaporate.  An  inch  of  rain 
over  an  acre  of  surface  is  equal  to  101  tons  of 
water.  In  mountain  districts  where  the  rain- 
gauge  can  only  be  visited  once  a  month,  the 
inside  can  should  be  large  enough  to  hold  20 
or  30  in.  Self-recording  rain-gauges  such  as 
those  by  Halliwell,  Negretti  and  Zambra, 
Beckley,  Richard,  &c.,  yield  most  valuable 
data  on  the  rate  of  fall,  the  intensity,  and  the 
duration  of  rain.  To  the  engineer  and  sur- 
veyor information  on  rainfall  is  most  important. 
Where  sewage  has  to  be  pumped  it  is  necessary 
to  know  what  has  to  be  provided  for  as  an 
average,  and  what  as  a  maximum,  so  that  the 
engineer  may  know  when  he  will  have  to  give 
up  pumping  and  have  resort  to  storm  over- 
flows. The  matter  of  water  supply  is,  to  a 
great  degree,  a  question  of  the  quantity  of  rain 
that  can  be  depended  on.  W.  M. 


Rams,    Hydraulic. 

RAMS.") 


(See     "  HYDRAULIC 


Reeve's  System  of  Sewage  Treatment. 

—In  this  system  a  chemical  precipitant  and 
deodorant  called  "  thamisin  "  is  used  in  both 
the  sewage  and  the  sludge  treatment.  The 
sewage  is  then  settled  in  tanks,  the  top  water 
drawn  off  and  treated  on  land  or  niters,  and 


the  sludge  disposed  of  on  land  as  a  fertilizer. 
The  process  is  in  use  at  Staines  and  Henley. 

Refuse  Collection.  -  -  The  powers  and 
obligations  of  local  authorities  in  the  matter 
of  refuse  removal  are  dealt  with  in  sections 
42  and  43  of  the  Public  Health  Act,  1875,  to 
which  reference  should  be  made.  Any  person 
who  obstructs  the  local  authority  in  carrying 
out  their  duty  under  these  sections  is  liable  to 
a  penalty  for  each  offence  of  £5,  whilst,  on  the 
other  hand,  if  the  authority  have  themselves 
undertaken  or  contracted  for  the  removal  of 
house  refuse  from  premises,  and,  after  written 
notice  from  the  occupier,  fail,  within  seven 
days,  to  remove  such  refuse,  they  are  liable  to 
pay  to  the  occupier  of  such  house  a  penalty 
not  exceeding  5s.  for  every  day  of  default. 

When  organising  a  system  of  refuse  collec- 
tion it  is  important,  at  the  outset,  to  know 
exactly  what  classes  of  material  are  to  be 
removed.  These  generally  include  domestic 
house  refuse,  trade  and  shop  refuse,  garden 
refuse,  and  street  refuse.  These  terms  are 
not  defined  by  the  Public  Health  Act,  1875, 
and  are  somewhat  indefinite  in  their  use  and 
application,  and  differences  occasionally  arise 
with  householders  as  to  what  classes  of  material 
are  to  be  removed.  It  is  important,  therefore, 
the  matter  should  be  made  as  clear  as  possible 
to  all  concerned  to  avoid  misunderstandings. 
Some  help  is  afforded  by  the  Public  Health 
(London)  Act,  1891,  which  contains  the 
following  definitions  : — 

"House  refuse"  means  ashes,  cinders, 
breeze,  rubbish,  night-soil  and  filth,  but  does 
not  include  trade  refuse. 

"  Trade  refuse  "  means  the  refuse  of  any 
trade,  manufacture,  or  business,  or  of  any 
building  materials. 

"  Street  refuse  "  means  dust,  dirt,  rubbish, 
mud,  road  scrapings,  ice,  snow,  and  filth. 

"Ash-pit "  means  any  ash-pit,  dust-bin,  ash- 
tub,  or  other  receptacle  for  the  deposit  of  ashes 
or  refuse  matter. 

The  material  to  be  collected  usually  consists 
in  varying  proportions  according  to  the  locality 
and  habits  of  the  people,  principally  of  cinder 


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REF 


and  ashes,  coal  and  coke,  fine  dust,  straw,  rags, 
waste  paper,  bones,  vegetable  and  animal 
refuse,  bottles,  glass,  crockery,  old  iron  and 
tins,  hardware,  kc.  Of  this  material  London 
is  said  to  produce  about  1^  million  tons  per 
annum  or  about  4  to  5  cwt.  per  head  per 
annum.  In  the  North  of  England  an  average 
of  about  8  cwt.  per  head  per  annum  is  collected. 
The  actual  amount  in  any  given  case  will, 
however,  vary  according  to  the  mode  of  collec- 
tion and  other  local  details. 

The  main  questions  to  be  considered  in 
connection  with  this  subject  may  be  dealt  with 
under  two  heads,  viz.  : — 

1.  The    means    of    temporary    storage    on 
premises  pending  "collection." 

2.  The  different  methods  of  collection. 
STOKAGE. — To  comply  with  the  requirements 

of  modern  sanitation  it  is  necessary  that  the 
accumulations  of  refuse  at  the  occupier's 
premises  be  as  small  as  possible,  and  that 
there  should  be  frequent  removals.  To  meet 
this  demand  there  is  nothing  better  than  the 
portable  galvanised  iron  pail  with  tight-fitting 
cover,  sufficient  to  hold  a  collection  not  exceed- 
ing one  week's  refuse.  In  many  parts  of  a 
town,  where  there  is  very  little  open  space  in 
the  rear,  a  daily  collection  of  refuse  is  often 
found  to  be  necessary  on  sanitary  grounds. 

Brick  or  fixed  ash-pits  are  very  undesirable, 
frequently  become  a  nuisance,  and  should  be 
abolished  wherever  possible. 

COLLECTION. — With  regard  to  the  different 
methods  of  collection,  whilst  it  is  impossible 
to  lay  down  any  one  system  as  being  suitable 
to  all  towns,  generally  speaking,  the  following 
systems,  or  some  modification  of  them,  are 
those  usually  adopted  : — 

THE  PORTABLE  IRON  PAIL  SYSTEM. — By  this 
method  the  refuse  is  deposited  in  small  port- 
able pails  placed  in  front  of  the  premises 
for  removal  by  the  scavengers  as  they  pass 
through  the  streets  on  their  rounds  at  certain 
fixed  intervals.  This  method  is  an  expedi- 
tious and  economical  one  so  far  as  the  carrying 
out  of  the  work  is  concerned,  as  it  saves  a  good 
deal  of  time  owing  to  the  fact  of  the  scavengers 
not  having  to  enter  upon  the  premises  to  carry 


out  the  refuse.  An  objection  is  often  raised 
in  the  better  class  residential  streets,  and  where 
there  is  shop  property,  to  the  display  of  dust 
receptacles  (of  great  variety  in  design)  for  an 
uncertain  period  of  time  in  the  front  fore- 
courts or  gardens  of  houses.  On  sanitary  and 
economical  grounds  the  method  is  a  good  one, 
but  these  are  frequently  outweighed  by  other 
considerations  often  more  or  less  sentimental. 

THE  "BELL  CART"  SYSTEM. — In  this  the 
carts  pass  through  the  streets  and  a  bell 
attached  to  the  horses  warns  the  householder? 
to  bring  out  their  refuse.  As  a  matter  of  fact 
occupiers  often  bring  the  refuse  out  before  the 
cart  arrives,  and  it  thus  becomes  blown  about 
or  upset  by  dogs  or  mischievous  boys.  The 
noise  of  the  bell  is  also  objected  to  by 
many. 

THE  "  I)  CART  "  SYSTEM  consists  in  the 
occupier  placing  a  card  bearing  the  letter  D  in 
large  type  in  the  window  when  a  call  from  the 
scavenger  is  required.  The  object  of  the  card 
is  to  save  time  on  the  rounds  of  the  collectors 
by  enabling  the  men  to  avoid  making  needless 
calls.  This  is  not  a  good  method,  on  sanitary 
grounds. 

CALLING  ON  RECEIPT  OF  NOTICE  from  the 
occupier  has  been  adopted,  but  the  plan  is  a 
bad  one,  as  on  the  neglect  of  the  occupier  a 
large  and  objectionable  accumulation  of  refuse 
may  arise.  The  amount  of  manual  and  team 
labour  required  from  day  to  day  is  also  an 
uncertain  and  variable  quantity,  and  therefore 
very  difficult  to  organise. 

PERIODICAL  COLLECTION  from  house-to-house 
at  fixed  intervals  without  notice  is  a  better 
plan,  and  more  certain  and  satisfactory  in  its 
results,  but  the  time  occupied — and  hence  the 
cost — will  be  greater. 

COLLECTION  FROM  PUBLIC  DUST  BINS  fixed 
by  the  local  authority  in  suitable  positions  in 
order  that  householders  in  their  immediate 
locality  can  place  their  refuse  into  them — their 
clearance  being  effected  by  the  authority  as 
necessary.  This  system  is  found  useful  in  the 
poorer  and  more  densely  populated  parts  of 
some  towns,  but  the  placing  of  the  bins  so  as 
to  avoid  objections  is  a  difficult  matter. 


346 


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MUNICIPAL   AND    SANITAEY  ENGINEEKING. 


REF 


DUST  AND  SCAVENGING  CARTS. — These  should 
be  sanitary  tip-carts  or  vans,  with  sliding  iron 
covers,  removable  in  sections,  similar,  for 
example,  to  the  "  Champion  "  dust  van  of 
the  London  County  Council  pattern  made  by 
Messrs.  Glover,  of  Warwick. 

The  principal  points  to  be  kept  in  view  in 
organising  a  proper  s}7stern  of  house  refuse 
collection  are  as  follows  : — 

1.  The  collections  must  be  frequent  so  as  to 
admit  only  of  small  accumulations,  thus  pro- 
ducing the  maximum  of  benefit  to  the  public 
health. 

2.  A   thoroughly    systematic    and    regular 
daily   routine   must  be  adhered  to,    so    that 
householders   may   know   as    precisely   as   is 
possible    when    the    scavengers   will   appear, 
thereby  giving  rise  to  the  minimum  of  incon- 
venience   to    the   public,    and  inducing  their 
fuller    co-operation,  which    will   considerably 
facilitate  the  work  of  collection. 

3.  There  should  be  an  inspector  whose  duty 
should  consist  of  making  house-to-house  visits 
to    see    that   all  refuse  is  properly  removed, 
to    supervise    the    collectors    when    on    their 
rounds,  and  to  attend  promptly  to  any  com- 
plaints. 

4.  Householders  should  be  well  informed  as 
to  what  is  house  refuse,  and  as  much  garden, 
vegetable,    and     other     organic     matter    as 
possible  should  be  consumed  or  buried  on  the 
premises. 

5.  There  should  be  a  proper  method  and 
recognised  charge  per  load  for  the  removal  of 
"  trade  refuse,"  in  the  absence  of  any  definite 
rule  providing  for  its  free  removal. 

6.  The  work  of  refuse  collection  is  essentially 
one  in  which  questions  of  economy  and  effi- 
ciency must   be    closely  studied,    bearing   in 
mind   the  sanitary  advantages  to  the  public 
health    to    be    gained    by    prompt     removal, 
especially  during  hot  weather.  W.  H.  M. 

Refuse  Destructors.  (See "  DESTRUCTORS.") 

Refuse  Disposal. — The  different  kinds  of 
"refuse"  collected  from  towns  may  be  de- 
scribed as  either  "house  refuse,"  "trade 


refuse,"  "  street  refuse,"  or  "  garden  refuse  " 
— the  first  three  descriptions  being  parti- 
cularly defined  by  the  Public  Health  (London) 
Act,  1891  (see  article  "  EEFUSE  COLLECTION  "). 
In  most  provincial  towns  the  total  amount  of 
material  collected  is  largely  augmented  during 
certain  parts  of  the  year  by  the  production  of 
considerable  quantities  of  "garden  refuse," 
which  has  an  important  bearing  upon  the 
question  of  "disposal"  as  well  as  that  of 
"  collection."  Most  authorities,  however,  find 
it  necessary,  on  the  ground  of  cost,  to  impose 
a  limit  upon  the  amount  of  garden  and  trade 
refuse  to  be  removed  at  the  public  expense. 

The  sanitary  disposal  of  refuse  collected 
from  human  habitations  is  a  matter  of 
primary  importance  and  a  first  step  towards 
the  building  up  and  maintenance  of  a  high 
standard  of  public  health. 

The  methods  of  disposal  selected  in  different 
districts  depend  largely  on  local  conditions, 
but  very  commonly  the  cheapest  plan  avail- 
able has  the  preference.  Frequently  this  may 
be  no  better  than  a  mere  makeshift,  and  the 
means  of  disposal  for  many  years  may  be 
nothing  better  than  a  hunting  about  from  one 
makeshift  to  another,  until,  finally,  other 
means  having  been  exhausted,  a  specially- 
built  refuse  destructor  (see  article  "  DESTRUC- 
TORS ")  becomes  an  absolute  necessity. 

The  chief  methods  employed  for  the  disposal 
of  the  refuse  collected  from  towns  are  the 
following: — 

(1)  Depositing  upon  waste  or  low-lying  land, 
filling  of  pits  and  excavations,  or  raising  the 
level  of  marsh  land,  such  sites  being  tem- 
porarily described  as  "  tips  "  or  "  shoots." 
This  is  a  very  favourite  and  cheap  means  of 
getting  rid  of  the  refuse,  where  suitable  sites 
exist  within  close  proximity  to  towns,  but  it  can- 
not be  considered  sanitary.  Refuse  tipped  in 
large  quantities  invariably  takes  fire  through 
spontaneous  combustion  due  to  the  heating  of 
the  vegetable  material  and  garden  refuse  con- 
tained therein,  and  when  once  started  usually 
continues  to  smoulder  and  smoke,  causing 
considerable  nuisance  from  smell  in  the 
immediate  vicinity  of  the  "  tip."  Such  sites 


847 


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are  usually  resorted  to  by  the  poor,  by  rag 
and  bone  pickers  and  such  like,  for  the 
purpose  of  sorting  over  the  material  deposited 
day  by  day,  and  it  is  thus  not  only  liable  to 
become  a  centre  of  infection,  but  offers  an 
unhealthy  occupation  to  persons  of  the  poorer 
class,  amongst  whom  sanitary  precautions  are 
pre-eminently  needful. 

(2)  Mixing  household  ashes,  dust,  &c.,  with 
pail  excreta  for  the  purpose  of  their  common 
disposal  by  sale  or  otherwise  to  farmers  for 
agricultural  purposes.     This  method  is  prac- 
tised in  some  of  the  northern  towns  where  the 
"  pail-system  "  for  the  removal  of  excreta  is  in 
use,  but  it  cannot  be  regarded  otherwise  than 
as  an  offensive  and  insanitary  business. 

(3)  Selling  or  giving  away  to  brickmakers 
is  a  less  objectionable  plan,  especially  where  the 
handling  and  picking  over  of  the  refuse  is  not 
permitted.    The  refuse  is  usually  screened,  and 
the  fine  ashes  mixed  with  the  brick,  and  forms 
the  "  firing  "  element,  whilst  the  "  breeze,"  or 
cinder   portion,  is    used   for   firing   the  kilns 
when  the  bricks  are  in  the  "  clamp."     Present- 
day   refuse   contains,    on    the    average,   less 
cinder  and  ashes  than  formerly,  owing  to  the 
extended  use  of  gas  fires,  and  the  large  pro- 
portion of  vegetable  material,  paper,  tins  and 
packings  of  all  kinds  of   artificial    foods  and 
preserved  fruits,  and  such  like. 

(4)  Mixing  with  sewage  sludge  and  plough- 
ing or  digging  into  the  soil  of  sewage  farms. 
This  may  be  done  to  advantage  where  suitable 
land  of   sufficient   quantity  can   be  obtained 
within  a  reasonable  distance  from  the  town, 
and  yet  at  the  same  time  sufficiently  free  from 
inhabited  dwellings  to  avoid  any  possibility  of 
nuisance  from  smell. 

(5)  Mixing  with  precipitated  liquid  sewage 
sludge,  or  with  pressed   sewage  sludge-cake, 
and  cremating  in  destructor  furnaces.      These 
processes  have  been  carried  out  at  Baling  and 
Leyton,   and,  though  costly,  may,  in  certain 
circumstances,  prove  a  convenient  means  of 
riddance    of    two     objectionable     classes     of 
materials. 

(6)  Crushing  or  pulverising  the  refuse  by 
machinery  and  employing  the  resulting  pro- 


duct as  a  manure  or  in  the  manufacture  of 
fuel  with  an  admixture  of  tar.  Fuel  briquettes 
are  manufactured  by  reducing  the  refuse  by 
means  of  a  crusher  to  a  fine  uniform  con- 
sistency, mixing  with  tar,  and  then  passing 
the  admixture  through  a  briquette  press.  The 
approximate  cost  of  a  plant,  including  a  mani- 
pulator or  crusher,  mixer,  press,  buildings, 
and  power  sufficient  to  deal  with  10,000  tons 
of  town  refuse  yearly,  is  about  i'2,500,  or,  say, 
5s.  per  ton  of  refuse  per  annum.  The  fuel 
thus  produced  has  an  average  calorific  value 
of  one-third  that  of  the  best  coal. 

(7)  Eiddling,  burning  the  cinders  and  vege- 
table refuse  to  generate  steam,  and  using  the 
fine  dust  in  connection  with  a  manure  manu- 
factory, the  old  iron  being  sold,  and  the  pots, 
&c.,  used  for  the  foundations  of  roads,  forms 
another  convenient  method  of  disposal  where 
conditions  are  suitable. 

(8)  Selling  by  tender   yearly  is  sometimes 
adopted  where  offers  can  be  obtained,  but  in 
the  majority  of  cases  this  is  not  possible. 

(9)  Barging  away  down  canals  to  country 
districts     is     done     by     some    metropolitan 
boroughs.     Although  this  entails  considerable 
expense,  in  many  cases  it  proves  less  costly 
than  burning  in  destructors. 

(10)  Taking   out   to    sea   in   specially-built 
hopper  barges  and  sinking  the  refuse  in  deep 
water  is  another  means  of  riddance  of  this 
material.    This  method  is  followed  at  Liver- 
pool, and  the  cost  of  disposal  is  about  Is.  6d. 
per  ton.     Care  has  to  be  exercised  in  selecting 
the  time,  tide,   and    site  for  discharging  the 
refuse  into  tbe  sea,  as  the  lighter  portions  are 
very  apt  to  float  ashore  and  cause  complaints. 

(11)  Utilising  by  "  sorting  "  by  hand  or  by 
machinery  and  selling  the  ingredients  for  use 
in  such  trades  or  manufactures  as  can  employ 
them,   as    is  done  in  dust  contractors'  yards. 
This  cannot  be  considered  a  satisfactory  mode 
of   treatment,    as   it   involves  a  good  deal  of 
handling    of   the    refuse,    and    is   necessarily 
an  unhealthy  operation   for   the   workpeople 
employed. 

(12)  Destroying   the    crude    refuse,  as  col- 
lected, by  fire  in  suitably-built  refuse  destruc- 


348 


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tors,  and  utilising  the  residual  clinker  and 
surplus  steam  generated  by  the  heat  of  com- 
bustion for  various  useful  purposes.  Where 
properly  carried  out,  this  is,  without  doubt, 
the  most  sanitary  method  of  disposal.  The 
plant  employed  should  be  of  the  latest  and 
most  approved  high  temperature  type,  and 
suitable  means  should  be  provided  to  dispense 
with  the  handling  of  the  refuse  as  far  as  is 
possible.  The  system  involves  a  considerable 
amount  of  capital  expenditure,  and  the  work- 
ing expenses  are  heavy,  but  where  suitable 
conditions  exist  some  part  of  the  expense 
may  come  back  from  the  sale  of  residuals 
and  the  use  of  surplus  heat.  (See  articles 
"DESTRUCTORS"  and  "REFUSE  COLLECTION.") 

W.  H.  M. 

Reinforced  Concrete  or  Ferro-Concrete. 

—Essential  Features — Expansion  and  Contraction 
— Adhesion  to  Steel  —  Expanded   Metal — Shear 
Stresses  —  Mixing    Concrete  —  Foundations  - 
Retaining     Walls  -  -  Bridges,     Sewers,    &c.  - 
Corrosion. 

ESSENTIAL  FEATURES.  —  The  principle  of 
reinforcement  is  that  Portland  cement  con- 
crete, which  is  very  strong  in  compression, 
is  used  in  conjunction  with  mild  steel,  which 
is  very  strong  in  tension,  and  the  two  are 
so  arranged  that  the  concrete  shall  take  the 
compressive  stress  while  the  steel  takes  the 
tensile  stress.  The  result  is  that  the  com- 
bination forms  a  cheap  and  very  efficient 
mode  of  construction  that  may  be  adapted 
to  almost  every  kind  of  structure.  Fire- 
resisting  floors  composed  of  these  materials 
first  took  the  form  of  steel  joists  embedded 
in  the  lower  side  of  a  concrete  slab.  This 
was  convenient  because  the  rolled  joists 
could  rest  upon  the  walls  without  any  special 
provision  to  receive  them,  and  the  concrete 
was  easily  filled  in  between  and  over  them. 
It  was  soon  found,  however,  that  to  give 
sufficient  covering  to  protect  the  lower  flange 
of  the  joists  from  the  action  of  fire  a  total 
thickness  was  required  that  was  not  economical, 
and  smaller  sections  were  adopted  for  the 
reinforcement,  such  as  tee  bars  and  Columbian 


sections,  which  were  placed  closer  together. 
This  produced  a  better  distribution  of  the  two 
materials,  and  a  very  simple  investigation 
showed  that  further  improvement  would  be 
obtained  by  using  the  steel  in  still  smaller 
sections  and  placing  it  very  near  the  lower 
surface  of  the  concrete. 

EXPANSION  AND  CONTRACTION. — Considerable 
doubt  was  felt  at  the  time  as  to  the  stability  of 
such  a  floor  under  the  action  of  heat,  owing  to 
the  popular  idea  that  steel  expanded  much 
more  than  concrete  under  the  same  increase 
of  temperature ;  but  it  was  shown  that  their 
expansion  and  contraction  were  almost  identi- 
cal. As  a  matter  of  fact,  the  linear  change 
for  a  given  variation  of  temperature  is  about 
15  %  less  for  concrete  than  for  steel ;  but 
when  the  actual  figures  are  compared  the 
difference  is  very  trifling.  Taking  the  range 
of  temperature  between  summer  and  winter 
as  70°  F.,  the  change  of  length  in  100  ft. 
produced  by  this  variation  of  temperature  will 
be  for  steel  0'546  in.,  and  forconcrete  0'464  in., 
the  difference  between  the  two  materials  in  a 
length  of  1  ft.  being  less  than  a  thousandth  of 
an  inch. 

ADHESION  TO  STEEL. — The  next  doubt  was 
whether  the  concrete  would  adhere  sufficiently 
to  plain  steel  rods  or  bars  to  enable  them  to 
receive  the  full  tension  without  drawing 
through  the  concrete,  and  numerous  patents 
were  obtained  for  bars  that  should  have  a  direct 
hold  upon  the  concrete,  such  as  twisted, 
corrugated,  indented,  and  stud  bars.  Experi- 
ment, however,  showed  that  there  was  a  strong 
adhesion  between  the  concrete  and  the  metal 
depending  upon  the  condition  of  the  surface  of 
the  latter  and  the  closeness  with  which  the 
former  was  packed  against  it.  The  best  adhe- 
sion was  obtained  when  the  steel  was  slightly 
rusted  all  over  and  painted  with  cement  wash 
just  prior  to  placing  the  concrete.  Prof. 
Bauschinger  found  the  ultimate  adhesion  to 
be  from  569  to  668  Ibs.  per  square  inch.  The 
Royal  Institute  of  British  Architects  recom- 
mend 100  Ibs.  per  sq.  in.  as  a  working 
allowance,  and  at  this  figure  the  embedded 
length  of  steel  that  would  leave  the  tensile 


349 


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strength  and  adhesion  equal  would  be  equal 
to  16,000  times  the  sectional  area  of  the  bar  in 
square  inches  divided  by  100  times  the  surface 

area  per  inch  in  length,  or  briefly  160-,  so 

s 

that  a  £  in.  square  bar  embedded  for  a  length 
of  not  less  than  20  in.  in  either  direction  from 
a  given  point,  would  be  equally  strong  against 
tearing  or  slipping,  and  similarly  a  1  in. 
round  bar  would  need  to  be  embedded  for  a 
length  of  40  in.  In  other  words,  40  times 
the  diameter  in  inches  gives  the  requisite 
overlap  or  length  for  embedding  any  plain 
round  or  square  bar  to  be  equally  strong  against 
tearing  or  slipping;  the  smaller  the  rods  the 


the  shear  stress.  The  first  and  most  obvious 
means  of  doing  this  was  by  turning  up  some 
of  the  tension  bars  diagonally  at  the  outer 
ends.  Where  four  bars  were  required  in  the 
centre,  only  two  were  wanted  beyond  the 
middle  third  of  the  span ;  but  the  four  were 
there,  so  they  were  bent  up  to  take  this  other 
duty.  This  was  only  a  crude  method  and 
not  altogether  sufficient.  Then  various  forms 
of  stirrups,  vertical  or  inclined,  were  intro- 
duced in  connection  with  the  longitudinal 
bars,  placed  closer  together  towards  the  ends 
where  the  shear  stress  was  greater.  These 
were  at  first  put  in  loose,  and  then  the  Kahn 
bar  was  introduced.  This  consisted  of  a 


Lines    of  princ/pai    compr-essive    stress 


Lines    of  principal,    tensjte   stress 


FIG.  1. — Loaded  Beam  failing  by  Shear. 

larger  the  proportionate  surface  for  a  given 
length. 

EXPANDED  METAL. — The  reduction  in  size  of 
the  rods  naturally  led  at  an  early  date  to  the 
substitution  of  wire  in  the  form  of  rectangular 
netting  ;  but  expanded  metal  with  lozenge- 
shaped  openings  soon  received  more  favour  than 
the  netting,  and  is  now  largely  used.  Over  the 
supports  it  is  kept  near  the  upper  surface  of 
the  concrete,  and  droops  in  the  centre  of  the 
span  to  be  near  the  lower  surface  ;  but  it 
does  not  permit  of  the  close  approximation  of 
the  stresses  that  is  given  by  rod  construction 
with  shear  members. 

SHEAR  STRESSES. — This  leads  to  considera- 
tion of  another  difficulty  which  arose  in  the 
early  designs.  Everybody  was  aware  of  the 
direct  stresses  of  compression  and  tension  in 
the  upper  and  lower  sides  of  the  beams  and 
how  to  calculate  them  approximately,  but  they 
overlooked  the  shear  stress  that  is  a  necessary 
accompaniment,  and  it  was  not  until  failures 
took  place  by  diagonal  cracks  near  the  ends 
of  the  beams,  as  in  Fig.  1,  that  attention  was 
called  to  the  need  of  providing  specially  for 


FIG.  2. — Curves  of  Stress  in  Beam. 

square  bar  placed  diagonally  with  longitudinal 
fins  or  webs  projecting  on  each  side  which 
were  sheared  at  intervals  and  bent  upwards  at 
an  angle  of  45°.  Then  various  forms  of 
shear  rods  were  introduced  twisted  tightly  on 
to  the  main  rods  at  such  intervals  as  were 
necessary  exactly  to  meet  the  shear  stresses, 
such  as  the  twisted  "  Paragon  "  wires  of  the 
British  Pieinforced  Concrete  Engineering  Co. 
The  actual  stresses  in  a  beam  may  be  repre- 
sented by  the  curves  in  Fig.  2.  Usually  the 
stresses  are  treated  as  if  they  were  simply 
longitudinal  and  transverse,  the  former  being 
tension  and  compression  and  the  latter  shear. 
They  can,  of  course,  be  met  in  this  way  by 
suitable  reinforcement ;  but  it  should  be 
remembered  that  the  shear  to  be  resisted  in  a 
ferro-concrete  beam  is  more  in  the  nature  of 
a  diagonal  tension,  and  should  be  provided 
for  by  diagonal  reinforcement.  While  these 
modifications  were  going  on  it  was  found  that 
further  economy  might  be  obtained  by  making 
the  floor  slabs  "continuous"  over  the  beams, 
and  the  beams  "continuous  "  over  the  columns; 
this  caused  reverse  stresses  over  the  supports 


850 


EEI 


MUNICIPAL   AND   SANITAEY   ENGINEEK1NG. 


REI 


The  elongation  of  a  test  piece  is  about  20  % 
in  a  length  of  8  in.,  with  a  contraction 
of  area  at  point  of  fracture  of  about  40  % 
ARRANGEMENT  OF  BUILDING. — The  general 
arrangement  of  a  ferro-concrete  building 
is  somewhat  as  follows  : — First,  the  founda- 
tions are  made  wide  enough  to  spread  the 


FIG.  3. — General  Type  of  Floor  Section. 

load  over  a  sufficient  area  of  the  subsoil  to 
avoid  risk  of  settlement,  being  wider  where 
the  piers  will  be  placed  to  support  the  floor 
and  roof  beams.  Instead  of  the  thick  mass  of 
concrete  seen  in  ordinary  foundations,  only 
about  one-third  of  this  thickness  is  required 


and  necessitated  the  inversion  of  the  system, 
which  was  a  comparatively  simple  matter, 
additional  longitudinal  bars  being  put  near  the 
upper  surface  over  the  supports  with  the  shear 
bars  projecting  downwards. 

When   this    system    of    construction    was 
adopted  for  the  walls  of   the  buildings   the 
floor    slabs    and    beams    were    con- 
nected to  them  in  the  same  way  as 
if  the  wall  was  one  side  of  an  inter- 
mediate support,  and  this  made  the 
connection     equivalent      to     "  fixed 
ends  "  in  girder  work. 

MIXING    CONCRETE.  —  For    all    re- 
inforced concrete  work  it  is  essential 
that    the    utmost   care    should    be    taken    in 
mixing  and  placing  the  concrete.     For  thin 
slabs   the    usual    proportion   is   one   part    of 
standard    Portland    cement    by    measure    to 
two   parts   of    clean,    coarse   sand,   and    four 
parts  of  larger  aggregate.      Before  the  days 
of   reinforced  concrete    it    was    con- 
sidered   sufficient   if    the    aggregate 
was  broken  to  pass  a  1J  in.  ring,  and 
for  this  new  purpose  it  was  reduced 
to  a  uniform  gauge  of  1  in.      Now 
the  material  is  generally  specified  to 
range  from  \  in.  to  f  in.,  the  vary- 
ing size  being  necessary  to  enaUe  it 
to  pack  closely.      For    fire-resisting 
floors     the     best     material    for    the 
aggregate    is   hard   brick   broken  as 
stated,  but   coke    breeze   has   many 
advocates.       Broken    pumice    stone 
makes  a  light  floor,  but  has   a   low 
crushing  strength,  while  broken  lime- 
stone calcines  and  loses  its  strength 
entirely,  and  flint  pebbles  burst  under 
the  action  of  heat ;    but  both  these 
materials  are  suitable  in  foundations. 
Clinker  may  contain  free   lime  and 
cause  disruption  by  delayed  slaking. 
The    steel    is    usually    in    the   form 
of   round  rods    of    mild   steel    from 
^  in.  to  1  in.   diameter,  having  an 
ultimate  tensile  strength  of  from  29  to  32  tons     in  the  case  of  ferro-concrete,  the  side  wings, 
per  square  inch,  and  a  modulus  of  elasticity     as  they  may  be  called,    of  the   foundations 


FIG.  4.- 


-Section  through  Floor  and  Column  showing 
Rein  i  orcement. 


of  about  29  million  pounds,  or  13,000  tons,     being    strengthened    so 

351 


that    they    act    as 


REI 


ENCYCLOPAEDIA   OF 


REI 


cantilevers.  Then  the  walls,  instead  of  being 
uniform  in  thickness,  consist  of  piers  and 
panels,  the  piers  to  carry  the  weight  of  the 
floors  and  roof,  and  the  panels  merely  to  form 
a  screen  from  pier  to  pier.  Eeinforcing  rods 
are  embedded  throughout.  At  each  floor 
ferro-concrete  beams  are  built  across  the 
room  from  pier  to  pier  with  cross-beams  in 


Coiumn 


FIG.  5 — Section  through  Foundation 
of  Column. 

the  case  of  large  spans,  and  then  floor  slabs  to 
form  the  filling  between  the  beams.  In  a  few 
cases  the  roofs  are  also  constructed  in  a  similar 
manner  with  flat  or  sloping  tops.  The  work  is 
not  finished  off  a  piece  at  once,  but  the 
rods  and  connections  are  put  in  place  con- 
siderably in  advance  of  the  concrete,  and 
timber  "  forms "  are  built  up  to  give  the 


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L    _ 

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FIG.  6. — Plau  of  Foundation  of  Column. 

required  external  dimensions  to  the  concrete. 
The  concrete  is  then  put  in  place  in  small 
quantities,  packed  round  the  rods  and  connec- 
tions, and  gently  rammed.  This  description 
is  sufficient  to  give  a  general  idea  of  the  mode 
of  construction  usually  adopted,  and  some  of 
the  details  are  shown  in  the  illustrations. 
Fig.  3  shows  a  typical  section  of  a  ferro- 


concrete floor,  consisting  of  main  beams,  cross 
beams,  and  floor  slab  supported  on  columns. 
All  junctions  are  made  gradually  by  45°  gusset 
pieces  or  fillets,  and  this  gives  an  interior  very 
much  the  appearance  of  heavy  timbering, 
especially  as  the  grain  of  the  wood  used  in 
supporting  the  concrete  sometimes  shows  on 
the  face  of  the  latter.  Fig.  4  shows  a  larger 


FIG.  1. — Section  of  Heavy  Foundation. 

section  through  a  column  and  floor  beam 
with  the  Paragon  shear  stirrups  twisted 
firmly  on  the  reinforcing  bars.  In  the  column 
the  bars  are  prevented  from  spreading  by 
encircling  .wires,  every  fourth  wire  being 
twisted  round  each  of  the  bars.  The  lower 
part  of  this  figure  shows  a  common  form  of 


Section 


]-C.I.  potnt 

FIG.  8. — Ferro-Concrete  Pile. 

reinforced  base  for  spreading  the  load  carried 
by  the  columns. 

FOUNDATIONS.  —  Fig.  5,  elevation,  and 
Fig.  6,  plan,  shows  more  fully  how  such  a 
foundation  is  constructed,  the  shear  stirrups 
here  being  placed  vertically  in  the  Hennibique 
manner.  When  bad  soil  has  to  be  contended 
with,  and  particularly  where  very  heavy  loads 


852 


REI 


MUNICIPAL  AND   SANITARY  ENGINEEEING. 


REI 


have  to  be  carried,  the  foundation  is  more 
elaborate,  as  in  Fig.  7,  the  load  being  spread 
by  rolled  joists  over  the  reinforced  concrete, 
and  this  in  turn  supported  by  ferro-concrete 
piles.  Fig.  8  shows  the  detail  of  a  pile.  The 
lower  end  is  shod  similarly  to  a  timber  pile, 


FIG.  9. — Steel  Cap  for  Driving  Pile. 

the  shoe  having  a  cast  point  and  wrought 
straps  ;  but  the  upper  ends  of  the  straps  are 
bent  inwards  and  embedded  in  the  concrete 
to  keep  them  in  place.  The  piles  are  driven 
by  an  ordinary  pile  engine,  or  better  by  a 
Lacour  steam  driver ;  but  the  top  needs  some 
protection  to  prevent  it  from  being  broken  up 
by  the  falling  ram.  Sometimes  a  wooden 


FIG.  10. — Section  of  Eetaining  Wall 
with  Counterforts. 

dolly  is  interposed.  The  more  general  method 
is,  however,  to  place  upon  it  a  steel  cap,  as 
Fig.  9,  with  sand  or  sawdust  in  it  to  dis- 
tribute the  blow.  To  drive  any  pile,  and 
particularly  a  concrete  pile,  with  the  least 
resistance,  it  is  important  to  keep  it  on  the 


move ;  and  this  is  the  advantage  of  the  steam 
driver  in  giving  a  rapid  succession  of  blows, 
not  leaving  time  for  the  soil  to  settle  against 
the  faces  of  the  pile.  After  driving,  5  in.  or 
6  in.  of  the  concrete  is  cut  away  from  the  top 


FIG.  11. — Sections  through  Bridge  and  Wing  Wall. 

to  enable  the  steel  rods  to  be  bonded  with  the 
superstructure. 

EETAINING  WALLS. — Perhaps  the  greatest 
departure  from  past  methods  of  construction 
occurs  in  the  new  form  for  retaining  walls. 
Hitherto  they  have  been  designed  to  resist 
thrust  and  overturning  simply  by  their  mass ; 
now  they  practically  have  no  mass  and  rely  for 


FIG.  12. — Section  through  Large  Sewer. 

stability  upon  their  strength  being  utilised  in 
carrying  the  mass  they  have  to  support.  Fig.  10 
shows  a  typical  wall  with  base  and  counterforts. 
The  earth  that  is  to  be  held  up  rests  upon  this 
base  so  that  the  wall  cannot  tilt  without  lifting 
it,  and  it  thus  becomes  a  main  element  of  the 
stability.  The  effect  of  the  counterforts  is 


M.S.E. 


353 


A  A 


REI 


ENCYCLOPAEDIA   OF 


RET 


solely  to  connect  the  base  to  the  vertical  wall ;     piles  ;  the  waterproofing  of  concrete,  £c.     It 


some  walls  have  them  omitted,  and  on  two  of 
the  American  railroads  plain  Land  T  sections 
are  largely  adopted  ;  but  the  omission  of  the 
counterforts  must  greatly  increase  the  risk  of 
failure  of  the  walls  owing  to  the  excessive 
stress  caused  at  the  junction  between  wall  and 
base. 

BRIDGES,  SEWERS,  &c.  —  Ferro-concrete 
bridges  of  widely  different  design  and  span 
have  been  constructed,  and  no  definite  type 
has  yet  been  determined  to  be  the  best. 
Some  of  the  early  ones  were  very  ugly ; 
but  numerous  bridges  of  good  architectural 
elevation  have  now  been  erected.  Fig.  11 
shows  a  plain  railway  bridge  with  abut- 
ments and  wing  walls.  The  construction  is 
very  simple  and  self-evident.  The  reinforcing 
bars  are  placed  in  two  sets,  near  the  inner 
and  outer  surfaces  of  the  arch,  those  on  the 
inner  face  are  doubled  in  the  centre  of  span, 
and  those  on  the  outer  face  are  doubled  from 
the  haunches  to  the  abutments. 

Fig.  12  shows  the  section  of  a  large  con- 
crete sewer  reinforced  on  the  Kahn  system. 
This  type  of  sewer  construction  has  been  very 
largely  used  in  America  and  is  applicable  to 
culverts,  tunnels,  conduits,  and  subways.  The 
details  are  of  course  modified  according  to  the 
nature  of  the  soil  passed  through.  The  finest 
illustration  of  ferro-concrete  construction  is, 
perhaps,  given  by  the  Marlborough  Blenheim 
Hotel,  Atlantic  City,  N.  J.  The  front  portion 
of  this  building  is  twelve  storeys  high, 
surmounted  with  a  dome,  30  ft.  diameter. 
The  entire  structure  is  built  of  reinforced  con- 
crete on  the  Kahn  system,  and  shows  that  with 
care  considerable  architectural  effect  can  be 
obtained. 

CORROSION. — The  Science  Committee  of  the 
Concrete  Institute  has  under  consideration  at 
the  present  time  various  important  details  con- 
nected with  this  form  of  construction,  among 
which  may  be  mentioned  the  standardisation 
of  formulae  and  notation  ;  the  conditions  under 
which  embedded  steel  may  corrode;  the 
characteristics  and  mode  of  using  various 
aggregates  ;  the  supporting  power  of  concrete 


is  now  generally  conceded  that  the  best 
protection  for  the  steel  is  to  let  it  get  slightly 
rusted,  then  to  brush  it  all  over  with  a  wire 
brush  sufficiently  to  remove  any  loose  rust, 
and  paint  it  with  a  wash  of  Portland  cement 
before  embedding  it  in  the  concrete.  Treated 
in  this  manner,  it  has  been  found  bright  after 
some  years  although  only  a  short  distance 
from  the  face  of  concrete  exposed  to  the  action 
of  sea  water.  Where  any  corrosion  has 
occurred  it  has  been  found  to  be  due  to  cracks 
permitting  of  direct  access  from  the  outside, 
or  to  the  action  of  sulphur  contained  in  the 
aggregate.  As  an  instance  of  the  protection 
afforded  to  the  metal  by  the  concrete,  some 
reinforced  concrete  waterpipes  (If  in.  thick) 
wrere  constructed  in  Grenoble  22  years  ago. 
After  15  years,  two  lengths  of  pipe  were 
raised  for  inspection,  and  it  was  found  that 
although  the  water  had  been  flowing  through 
them  and  they  had  been  embedded  in  soil 
for  all  those  years  with  only  f  in.  of  Portland 
cement  concrete  protecting  the  steel,  the  metal 
was  as  bright  as  on  the  day  it  had  been  put 
in.  H.  A. 

Retaining  Walls  are  strong  walls  of 
masonry,  brickwork,  or  concrete,  built  at  the 
side  of  an  excavation  to  support  the  adjacent 
earth  and  resist  its  thrust,  such  as  those  round 
a  sunk  reservoir  or  dock,  at  the  sides  of  an 
urban  railway  cutting,  or  on  a  sea  front  or 
canal.  The  thrust  is  the  primary  element  for 
consideration  ;  it  varies  with  the  nature  of  the 
soil  and  the  difference  of  its  level  on  the  two 
sides  of  the  wall.  A  heap  of  earth  left  to 
itself  will  in  course  of  time  weather  down  to 
an  angle  with  the  horizontal  called  its  angle 
of  repose  or  natural  slope,  varying  generally 
between  25°  and  45°,  as  in  the  following 
tables. 

Kankine,  <£  = 

Dry  sand  clay  and  mixed  earth 

Damp  clay 

Wet  clay 

Shingle  and  Gravel 

Peat 


37  to  21 

45 

17  to  14 
48  to  35 

to  14 


45 


354 


RET 


MUNICIPAL    AND    SANITAEY   ENGINEERING. 


RET 


Unwin,  0  = 

Fine  dry  sand         .         .         .     37  to  31 

Sand,  wet       ...  26 

,,       very  wet       ...  32 

Vegetable  earth,  dry       .  29 

,,     moist    .         .     49  to  45 

,,  ,,      very  wet       .  17 

,,  ,,      consolidated 

and  dry        .  49 

Loamy  earth  ...  40 

Clay,  dry        ...  29 

„     damp,  well  drained        .  45 

,,     wet        ....  16 

Gravel,  clean          ...  48 

,,       with  sand  ...  26 

Loose  shingle          ...  39 

Moles  worth,  (/>  = 

Gravel  average       ...  40 

Dry  sand         ....  38 

Sand      ...  22 

Vegetable  earth      ...  28 

Compact  earth        ...  50 

Shingle  ....  39 

Bubble  ....  45 

Clay,  well  drained  .         .  45 

„      wet        ....  16 

Author's  Practice,  <£  = 

Wet  sand,    clay  or  vegetable 

earth  .....  15 

Dry    sand,    clay  or  vegetable 

earth 30 

Loamy   earth,   loose    shingle, 

clay  well  drained         .         .  40 

Firm    gravel     and    hard    dry 

vegetable  earth  ...  45 

If  the  earth  were  left  without  support  and 
with  a  vertical  face,  it  is  assumed  that  the 
first  failure  would  be  the  breaking  away  of  a 
wedge  of  earth  contained  between  the  vertical 
face  and  the  bisection  of  the  angle  between  the 
vertical  and  the  line  of  natural  slope,  called 
the  line  of  rupture,  indicated  by  the  shaded 
portion  in  Fig.  1.  It  is  this  wedge  of  earth 
that  the  retaining  wall  has  to  support,  and 
the  wedge  action  due  to  its  shape  and  weight 
causes  a  tendency  to  slide  down  the  line  of 
rupture  and  produce  a  horizontal  thrust 


against  the  back  of  the  retaining  wall, 
increasing  uniformly  in  intensity  from  the 
top  to  the  bottom,  with  the  centre  of  pressure 
at  one-third  the  height,  as  shown  at  P  in 
Fig.  2,  which  shows  the  section  of  an  ordinary 
retaining  wall.  The  wall  is  so  designed  that 
its  weight  combined  in  a  parallelogram  of 
forces  with  the  thrust  of  the  earth  shall  give 
a  resultant  passing  through  the  base  at  one- 
third  of  its  thickness  from  the  outer  edge. 
This  produces  a  distribution  of  the  reacting 
forces  in  the  foundation  shown  by  the  triangle 
below  the  wall,  with  a  maximum  compression 
at  the  outer  edge,  reduced  to  nothing  at  the 
back.  Then  the  moments  of  the  forces  in 
action  will  be  equal,  Px  =  Wy.  When  the 
resultant  falls  within  the  middle  third  of  the 
base  it  means  no  more  than  that  there  will  be 
no  tension  on  the  inner  edge  of  the  base.  It 
is  generally  supposed  that  under  these  con- 
ditions any  wall  will  be  safe,  but  this  is  not 
necessarily  the  case.  With  a  high  wall  its 
weight  may  increase  the  compressive  stress 
beyond  the  safe  limit,  and  with  a  low  wall  it  is 
often  possible  to  be  within  safe  limits  when 
the  resultant  is  only  one-fourth  of  the  thickness 
from  the  outer  edge.  The  thrust  of  the  earth 
may  be  found  entirely  by  calculation,  or  partly 
by  calculation  and  partly  by  graphical  con- 
struction. By  calculation  the  formula  is 

,  or,  the  same  thing 


T  =      wh  2  tan  2 


in  another  shape,  T  = 


' 


,  where 


.       , 

1    +  8111  (/> 

T  =  horizontal  thrust  in  Ibs.,  w  =  weight  of 
earth  in  Ibs.  per  cubic  foot,  h  =•  height  in  feet, 
(f)  =  angle  of  natural  slope  in  degrees.  The 
second  method  is  to  deal  with  1  ft.  run  of  this 
wall  and  earth,  mark  the  centre  of  gravity  of 
the  wedge  of  earth  as  in  Fig.  3,  and  drop  a 
vertical  line  to  cut  the  line  of  rupture.  Calcu- 
late the  weight  of  the  wedge  of  earth  and  set 
the  amount  up  to  scale  from  the  intersection 
with  the  line  of  rupture,  from  which  point  also 
draw  a  horizontal  line,  and  from  the  upper  end 
of  the  marked  amount  draw  a  line  parallel 
with  the  line  of  rupture.  This  will  cut  off  a 
horizontal  distance  equal  to  the  total  thrust 


355 


A  A  2 


RET 


ENCYCLOPEDIA   OF 


RET 


measured  with  the  same  scale.  The  centre  of 
gravity  of  the  wall  is  then  found  by  setting  off 
the  width  of  base  on  each  side  of  the  top,  and 
the  width  of  top  on  each  side  of  the  base,  and 
drawing  diagonal  lines  which  will  intersect  at 
the  centre  of  gravity  of  the  wall.  Then  trans- 
ferring the  thrust  in  the  same  horizontal  line 
beyond  the  centre  of  gravity  of  the  wall  and 
setting  off  the  weight  of  1  ft.  run  of  the  wall 
to  the  same  scale  below  it,  the  parallelogram 
is  completed  and  the  resultant  produced  to  cut 
the  base.  Wherever  the  resultant  cuts  the 
base,  if  tension  may  be  allowed,  the  formula 


ir 

pression  at  outer  edge  will  be  §  X   y,  where 

IT"  ==  weight  of  wall  and  d  =  distance  of 
resultant  from  outer  edge  of  base.  It  will  be 
self-evident  from  Fig.  2  that  a  wall  of  the 
section  shown  will  be  more  efficient  than  an 
upright  wall  of  parallel  thickness,  as,  owing  to 
the  battering  face,  the  centre  of  gravity  is 
thrown  further  back  and  the  weight  acts  with 
a  greater  leverage.  The  usual  batter  varies 
from  1  to  3  in.  per  foot  according  to  circum- 
stances, and  the  courses  of  the  brickwork  or 
masonry  are  always  laid  at  right  angles  to 


FIG.  1. 


FIG.  1. — Wedge  of  Earth  pressing  against  Wall.         FIG.  2. — Distribution  of  Pressures  on  Wall. 

FIG.  3.— To  find  Stability  of  Wall. 


for  the  stress  at  outer  and  inner  edges  will  be 

W       M 

~r  i  77  >  where  W  =  weight  of  1  ft.  run  of 

A  £ 

wall  in  Ibs.,  cwts.,  or  tons,  A  =  sectional  area 
of  base  in  square  feet  =  thickness  X  1  ft., 
M  =  bending  moment  =  weight  of  wall  X 
distance  in  feet  from  centre  of  base  to  point 
where  the  resultant  cuts  it,  Z  —  section 
modulus  of  base  =  \  of  the  width  of  base  in 
feet  squared.  The  +  value  gives  the  com- 
pression per  square  foot  at  outer  edge  and  the 
-  value  gives  the  compression  or  tension,  as 
the  case  may  be,  per  square  foot  at  the  inner 
edge.  When  no  tension  can  be  allowed  this 
formula  will  apply  so  long  as  the  resultant 
does  not  pass  beyond  the  middle  third,  but  if 
it  passes  beyond  this  the  formula  for  the  com- 


the  face.  The  back  of  the  wall  is  usually 
stepped  in  half-brick  (4^  in.)  set-offs,  at  such 
intervals  that  the  mean  line  is  vertical,  and 
the  top  is  surmounted  by  a  stone  coping, 
or  blue  bricks  on  edge  laid  in  cement 
mortar.  From  three  to  six  courses  of  foot- 
ings are  usually  carried  out  beyond  the 
face  of  the  wall  but  none  on  the  back,  and 
the  wall  is  usually  built  on  a  cement  con- 
crete foundation,  thicker  at  the  front  than 
the  back,  in  order  that  the  under-side  may 
be  level.  The  earth  filled  in  at  the  back 
of  the  wall  must  be  punned  in  1  ft.  layers 
inclined  away  from  the  wall  to  reduce  the 
tendency  to  slip,  and  if  there  is  an  existing 
bank  to  the  earth  it  must  be  benched,  or  cut 
in  steps,  before  the  filling-in  takes  place. 


856 


RET 


MUNICIPAL   AND    SANITAKY   ENGINEERING. 


RET 


When  the  wall  has  earth  on  one  side  and 
nothing  on  the  other,  provision  must  be 
made  for  carrying  off  any  water  that  may 


walls.  A  complete  design  for  a  retaining  wall 
is  shown  in  Fig.  4.  A  wall  to  resist  the 
pressure  of  water  may  be  designed  upon 


collect  behind  it  by  forming  vertical  rubble     exactly  the  same  principles,  bearing  in  mind 


or^fyLue    vitrifies/    capping 

-Surface    of 


/ILL    hecro/ers    crC 
to/o    of  e&ch 
sec -off 


ench     afror/n 
cont/nuous 
horizontal. 


FIG.  4. — Complete  Design  for  Retaining  Wall. 


drains  at  intervals  of  10  or  12  ft.  with  weep 
holes  near  the  bottom,  and  connecting  them 
by  a  horizontal  French  drain.  This  will  not 
be  required  in  the  case  of  reservoir  or  dock 


that  the  natural  slope  of  water  is  nil  and  that 
the  assumed  line  of  rupture  will  therefore  be 
at  45°.  When  there  is  earth  on  one  side  of 
a  wall  and  water  on  the  other,  the  thrust  from 


357 


RET 


ENCYCLOPEDIA   OF 


RET 


each  must  be  worked  out  and  both  resultants 
should  generally  fall  within  the  middle  third 
of  the  base,  but  the  actual  stresses  should  be 
calculated  in  every  case.  The  triangle  from 
which  the  thrust  is  scaled  in  Fig.  3  may  be 
set  off  in  another  way,  which  is  rather  more 
convenient,  as  it  applies  equally  to  walls  with 
sloping  backs,  battering  or  overhanging.  In 
Fig.  5  is  shown  a  concrete  tank  wall,  with 
the  excavated  material  banked  against  the 
outside,  and  the  thrust  triangle  drawn  by 


pression  at  A,  and  270  Ibs.  or  0*12  ton  per 
square  foot  compression  at  B.  From  the  com- 
bined thrusts  of  earth  and  water  the  stresses 

W         M         4800         4800  X  1'5 

will  be   —   +    rr  =       r~      '    i  /-.    „   4z\     = 
A          Z  ^  (1  X  42) 

1200  +  2700  =  3,900  Ibs.  or  1'74  tons  per 
square  foot  compression  at  B,  and  1,500  Ibs. 
or  0'67  ton  per  square  foot  tension  at  A. 
In  the  case  of  the  division  wall  Fig.  6,  the 

W  ,    M      6280   .    6280  X  1'5 

stresses  will  be  --  +  —  =  — • —-  +  ~y- 

A         Z  o  ^  (1  X  o  ) 


Water*    62'/2  Lbs 
per  abb 


.    k  -+'.'</- 

FIG.  5.—  Concrete  Tank  Wall. 

setting  up  the  weight  of  wedge  vertically 
above  one-third  of  the  height,  drawing  a  line 
at  right  angles  to  the  back  of  wall  for  the 
direction  of  the  thrust,  and  then  setting  off  the 
angle  of  the  wedge  £  (90  —  </>)  to  complete  the 
triangle.  Any  division  wall  in  the  tank,  unless 
perforated  and  used  as  a  strut  only,  must  be 
sufficiently  thick  to  resist  the  full  pressure  of 
water  on  one  side  of  it  while  empty  on  the 
other,  as  in  Fig.  6.  Having  drawn  graphic- 
ally the  forces  and  their  resultants,  the  stresses 
would  be  calculated  as  follows.  In  Fig.  5  the 
stresses  due  to  the  thrust  of  earth  only  will  be 


W  ,  M      4320  ,   4320  X  \ 

A±Z~-   —  ± 


=  108°  ±  81°  = 


1,890  Ibs.,  or  0'85  ton  per  square  foot  com- 


*.--.- ± 

FIG.  6.— Concrete  Division  Wall  in  Tank. 

=  1046  +  1570  =  2,616  Ibs.  or  1-66  tons  per 
square  foot  compression  at  C  and  524  Ibs. 
or  0'24  ton  per  square  foot  at  D.  It  will 
therefore  be  evident  that  the  walls  might  have 
been  reduced  in  thickness  probably  by  6  in. 
When  a  retaining  wall  supports  a  bank  of 
earth  sloping  upwards  above  its  own  height,  it 
is  said  to  be  surcharged,  and  the  thrust  is 
greatly  increased.  The  simplest  way  of  find- 
ing the  thrust  is  by  using  Rankine's  graphic 
method  shown  in  Fig.  7,  and  worked  as 
follows  : — Let  A  B  C  D  be  the  section  of  the 
proposed  wall,  D  E  the  line  of  surcharge,  the 
natural  slope  and  line  of  rupture  being  drawn 
as  usual.  Then  set  up  B  F  making  angle  0 
with  back  of  wall,  produce  E  D  to  F,  bisect 


358 


RET 


MUNICIPAL    AND    SANITAEY   ENGINEERING. 


RET 


B  F  in   G,  and  from  G  as  eentre  draw  the 
semicircle  B  F.    From  D  drop  a  perpendicular 


-i 

FIG.  7. — Surcharged  Retaining  Wall. 

on  to  B  F  cutting  it  in  J,  and 
continue  D  J  through  to  H. 
From  centre  F,  with  radius 
F  H,  cut  B  F  in  K.  Then  the 
horizontal  thrust  will  be  found 
by  the  formula  T  =  %  w  (B  A')2 
=  J  X  112  X  52  =  1,400  Ibs. 
acting  at  one-third  of  the  height 
as  shown  at  M  L.  Draw  L  N 
parallel  with  the  line  of  sur- 
charge, and  cut  it  off  by  the 
vertical  M  N,  then  N  L  gives 
the  actual  thrust  against  the 
wall.  Drop  a  line  through  the 
centre  of  gravity  of  the  wall, 
and  produce  N  L  to  intersect 
it  in  P ;  then  P  R  —  thrust, 
and  P  Q  =  weight  of  wall, 
the  resultant  P  S  cuts  the  base 
at  T,  3  in.  from  centre  of  base, 
the  vertical  component  being 
4,680  Ibs.  Then  the  maximum 


.....     W  ,   M      4680   .    4680    X    i 

stresses  will  be  -r-  +  -^  =  -r— -  ±  ,-r—    — —£• 

Z         4'5         £(1  X  4'52) 

=  1040  +  347  =  1,387  Ibs.  or  0'62  ton  per 
square  foot  compression  at  A,  and  693  Ibs.  or 
0'31  ton  per  square  foot  compression  at  B.  The 
maximum  safe  load  on  brickwork  being  from 
3  to  10  tons  per  square  foot,  according  to  quality, 
there  is  an  ample  margin  of  safety,  but  if 
the  wall  is  reduced  in  thickness  the  maximum 
stress  will  rapidly  increase,  so  that  it  may  be 
left  as  given.  When  the  slope  of  surcharge  is 
parallel  to  natural  slope,  B  K  =  B  F.  When 
the  earth  at  the  back  of  a  retaining  wall  is 
loaded  in  any  way,  some  allowance  must  be 
made  for  the  increased  thrust  produced  against 
the  wall.  There  is  no  generally  recognised 
method  of  doing  this,  but  the  following  is  put 
forward  as  a  reasonable  suggestion  for  the 
purpose.  Let  two  loads  be  carried  as  in 
Fig.  8,  Wi  =  1  ton  per  foot  run,  W2  =  4  tons 
per  foot  run,  at  distances  of  2  ft.  and  3  ft.  from 
back  of  wall.  From  the  point  of  application 
of  the  load  IJ'i  draw  a  line  parallel  to  the  line 
of  rupture  to  cut  the  back  of  the  wall,  and 
assume  this  to  be  the  point  of  application  of 


FIG.  8.— Wall  Loaded  at  Back 


359 


RET 


ENCYCLOPAEDIA   OF 


RIC 


the  thrust  from  this  load,  the  value  being 
found  by  triangle  in  the  ordinary  way.  Com- 
bine this  thrust  with  the  weight  of  the  wall, 
and  draw  the  resultant.  Combine  this 
resultant  with  the  thrust  due  to  the  weight 
of  the  wedge  of  earth  and  draw  the  second 
resultant ;  then  combine  this  resultant  with 
the  thrust  from  load  JF2,  found  as  above 
described,  to  give  the  final  resultant  cutting 
the  base  as  shown.  Then  the  vertical  com- 
ponent of  the  final  resultant  being  72  cwts. 
and  the  point  of  intersection  with  the  base 


I*    „-,  -42.  €   r>aa> 
t-2'S  -I 


FIG.  9. — Ferro- Concrete  Retaining  Wall. 

0'9  ft.  from  the   toe  of  wall,  the  maximum 

W  72 

compression  will  be  §  -y  =  §  X  f-r.  =  oSJewts. 

id  U  9 

=  2§  tons  per  square  foot.  When  a  reservoir 
is  built  above  the  surface  of  the  ground,  the 
containing  wall  may  be  very  much  lightened 
if  built  in  reinforced  concrete.  Fig.  9  shows 
a  section  through  the  600,000  gallon  reinforced 
concrete  reservoir,  80  ft.  diameter  and  15  ft. 
deep,  constructed  at  Cos  Cob,  Conn.,  U.S.A. 
It  is  founded  on  solid  rock  and  is  without  any 
surrounding  fill,  thus  making  some  exterior 
embellishment  very  desirable.  Accordingly 


the  wall  was  designed  with  a  cornice  and  a 
slightly  projecting  base,  and  the  flat  belt 
between  was  relieved  with  a  series  of  arched 
indented  panels,  40  in  number,  giving 
somewhat  the  effect  of  an  arcade.  The 
concrete  wall  has  a  4- in.  lining  of  brick  laid 
in  cement  mortar  to  protect  the  waterproofing 
coat.  It  is  reinforced  circumferentially  with 
steel  cable,  varying  in  diameter  from  1^  in.  at 
the  base  to  f-  in.  at  the  top,  forming  a  con- 
tinuous spiral  with  12-ft.  splices  made  with 
16  Crosby  clips  where  the  ends  of  two 
sizes  of  cable  are  joined.  The  pitch  of  the 
spiral  varies  somewhat  as  indicated  on  the 
drawing,  but  is  in  general  about  1  ft.  Inside 
the  cable  spiral  is  a  continuous  sheet  of  3  in. 
by  12  in.  mesh  Clinton  wire  fabric,  placed  in 
vertical  strips  which  extend  6  ft.  into  the  floor 
foundation.  About  10  days  after  the  filling 
of  the  wall-forms  had  been  completed  the 
forms  were  removed  and  the  derrick  was  taken 
out  of  the  tank.  The  floor  was  then  concreted 
to  an  even  surface,  and  a  4-ply  waterproofing 
coat  of  Hydrex  felt  was  applied  to  the  inner 
surface  of  the  wall  in  vertical  strips  and  to 
the  tank  floor.  Hydrex  compound  was  used 
to  cement  the  layers  of  felt  together.  A  4  in. 
protective  covering  of  concrete  was  laid  over 
the  floor  of  the  reservoir  on  the  waterproofing 
coat  and  extending  a  little  way  up  the  side  to 
give  a  footing  for  the  4  in.  brick  wall  lining. 
The  bricks  were  laid  with  cement  mortar  with 
a  solid  backing  of  mortar  between  brick  and 
waterproofing.  H.  A. 

Richmond  Sewage  Disposal  System.— 

The  method  of  treatment  at  the  Richmond 
Main  Sewerage  Board's  works  at  Mortlake 
consists  of  chemical  precipitation,  filtration 
through  beds  of  gravel  and  sand,  and  reduction 
of  sludge  by  filter  presses.  There  are  eleven 
precipitation  tanks,  each  100  ft.  by  30  ft.  by 
7ft.  6  in.  deep,  the  total  capacity  being 
1,210,000  gallons.  These  tanks  can  be  worked 
either  on  the  intermittent  or  continuous  flow 
system.  The  effluent  is  further  dealt  with  on 
eight  filter  beds,  four  high  and  four  low-level 
beds,  each  107  ft.  by  100  ft.  The  filtering 


360 


RIS 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


HIS 


material  averages  '6  ft.  6  in.  deep,  and  consists 
of  a  layer  of  9  in.  pipes  overlaid  by  gravel  and 
sand  of  graduated  sizes,  finished  with  3  in. 
of  loam,  and  sown  down  with  grass.  The 
filters  have  been  in  use  for  some  years  with 
occasional  renovation  of  the  surface  soil.  The 
board's  engineer,  Mr.  W.  Fairley,  A.M.I. C.E., 
states  that  the  process  of  precipitation  con- 
sists of,  first,  a  small  dose  of  carbolic  acid  and 
iron  salts  mixed  with  the  sewage  as  it  enters 
the  pump  well.  After  being  pumped  the 
sewage  receives  about  4  or  5  grains  per  gallon 
of  milk  of  lime  and  7  grains  per  gallon  of  a 
mixture  of  sulphate  of  alumina,  iron,  &c. 
The  tank  liquor  is  then  passed  through  the 
niters,  from  the  outlets  of  which  it  is  discharged 
on  the  ebb  tide  into  the  Thames.  The 
expense  of  chemicals  per  million  gallons  varies 
from  22s.  to  25s. 

Rising  Mains. — Rising  mains  are  laid  in 
cast-iron  pipes  with  a  thickness  of  metal 
suited  to  the  pressure  to  be  withstood.  They 
should  be  in  as  direct  a  line  as  possible,  with 
the  least  possible  number  of  bends,  and  should 
be  of  ample  diameter  to  pass  the  volume  of 
water  required  without  creating  undue  loss 
from  friction  in  forcing  the  water  through 
them.  In  deciding  upon  the  internal  diameter 
it  should  be  remembered  that  most  probably 
in  the  course  of  a  few  years  the  discharging 
capacity  of  the  pipes  will  become  considerably 
reduced  from  incrustation,  in  which  case  a 
large  increase  of  head  may  be  thrown  upon 
the  pumping  engines.  The  question  of  size 
is  one  which  requires  very  careful  considera- 
tion, as  every  additional  inch  in  diameter 
involves  a  material  increase  in  weight  of 
metal  in  a  long  pipe  line,  whilst  the  error  of 
providing  too  small  a  main  results  in  a  larger 
coal  bill  to  be  paid  annually  owing  to  the 
machinery  having  to  work  against  a  head 
partly  due  to  the  increased  frictional  resist- 
ance. The  interest  upon  the  additional 
capital  outlay  involved  by  a  main  of  larger 
diameter,  or  on  the  cost  of  duplicating  a  main 
which  may  have  become  insufficient  for  present 
requirements,  must  therefore  be  set  against 


the  estimated  annual  reduction  of  coal  bill 
which  would  result  from  the  provision  of 
increased  main  capacity,  the  pumping  engines 
having  to  develop  less  power  to  raise  the  same 
quantity  of  water.  "Where  the  mains  are  of 
ample  capacity  the  extra  head  due  to  friction 
will  not  exceed  about  20  ft.  per  mile.  The 
incrustation  in  a  main  often  occurs,  not  as  a 
uniform  coating  around  its  internal  surface, 
but  in  numerous  irregular  nodules  or  lumps, 
thus  greatly  retarding  the  flow.  The  nature 
of  the  incrustation  will  of  course  depend 
greatly  upon  the  character  of  the  water 
pumped.  For  economical  working  the  velocity 
of  flow  through  the  main  should  not  exceed 
from  2£  to  3  ft.  per  second  or  the  friction  will 
be  greatly  increased.  The  calculations  for 
engine  power  and  main  capacity  in  connection 
with  the  recent  Coolgardie  water  scheme  were 
based  on  an  assumed  flow  of  about  2  ft.  per 
second  through  a  pipe  30  in.  in  diameter. 
The  frictional  effect  of  increase  of  velocity  in  a 
main  is  shown  by  the  following  comparison  of 
velocities  in  a  clean  12  in.  pipe  : — A  velocity 
of  3  ft.  per  second  gives  a  frictional  head  of  a 
little  over  3  ft.  per  1,000  ft.  of  length,  whilst  a 
velocity  of  5  ft.  gives  a  head  of  8'5  ft.  per  1,000ft. 
The  frictional  resistance  in  a  pipe  increases  in 
the  proportion  of  the  square  of  the  velocity  of 
flow,  and  it  is  thus  readily  seen  that  a 
very  material  waste  of  power  may  arise 
from  this  cause.  In  the  same  way  a  great 
loss  of  "  head,"  due  to  insufficient  main 
capacity,  occurs  in  the  mains  of  a  distributing 
system. 

On  long  lines  of  rising  main  of  considerable 
head,  reflux  valves  should  be  inserted  at  suit- 
able intervals  in  order  that  the  pumps  may  be 
relieved  of  pressure,  and,  in  the  event  of  a 
burst  pipe,  one  section  of  the  main  only  will 
be  discharged  to  waste,  and  that  under  a 
much  reduced  head  or  pressure.  A  relief 
or  safety  valve  should  also  be  provided  in 
the  delivery  pipe  close  to  the  air  vessel, 
and  should  be  weighted  a  little  above 
the  usual  working  pressure  so  as  to  give 
relief  in  the  pipes  in  case  of  stoppage 
therein. 


361 


RIV 


ENCYCLOPEDIA  OF 


RIV 


Rivers  Boards :  Central  Authority.— 

As  a  result  of  the  Sewage  Commission  of 
1869,  the  first  central  authority  having  con- 
trol over  river  purification  was  established, 
viz.,  the  Local  Government  Board.  The  Public 
Health  Act  Amendment  Act  of  1875  stipu- 
lated that  the  Local  Government  Board  should 
only  sanction  the  raising  of  loans  for  sewage 
disposal  after  the  schemes  had  been  favour- 
ably reported  upon  by  an  inspector  of  that 
Board,  who  had  held  a  local  inquiry.  The 
control  exercised  by  the  Local  Government 
Board  has  been  mainly  confined  to  criticism 
of  schemes  thus  brought  before  them.  The 
Mersey  and  Irwell  Joint  Committee  was 
formed  in  1891  as  a  result  of  a  petition  from 
the  county  councils  of  Lancashire  and 
Cheshire,  and  obtained  special  powers  under 
the  Mersey  and  Irwell  Act,  1892.  A  similar 
committee,  the  West  Riding  Rivers  Board, 
was  appointed  by  Provisional  Order  in  1893, 
followed  by  the  West  Riding  of  Yorkshire 
Rivers  Act  in  1894.  The  function  of  these 
boards  and  others  of  a  similar  character,  such 
as  the  Ribble  Joint  Committee,  is  mainly 
administrative,  their  chief  activity  being 
directed  to  see  that  local  authorities  and  manu- 
facturers duly  carry  out  the  provisions  of  the 
Rivers  Pollution  Acts  in  their  respective  dis- 
tricts. Although  the  inspectors  of  these  rivers 
boards  in  their  personal  character  are  often 
very  helpful  to  authorities  by  indicating 
measures  which  may  properly  be  taken  in 
certain  cases,  the  Board  takes  no  responsibility 
officially  for  such  advice,  for  which,  of  course, 
no  remuneration  is  given,  nor  are  experi- 
mental investigations  undertaken  for  other 
than  the  private  information  of  the  Board. 

The  Massachusetts  State  Board  of  Health, 
which  was  founded  in  1886,  has  from  the 
first  undertaken  experimental  researches  of 
great  and  fundamental  importance.  The  re- 
sults of  these  are  published  annually  in 
Reports,  and  the  officials  of  the  Board  not  only 
examine  schemes  and  supervise  the  construc- 
tion of  works,  but  also  continually  inspect  the 
works  in  operation. 

Similar  State  Boards  have  been  founded  in 


other  parts  of  the  United  States,  e.g.,  Washing- 
ton, New  York,  and  Ohio. 

In  1901  an  Imperial  Council  of  Health, 
having  jurisdiction  over  streams,  was  formed 
in  Germany  by  several  Federal  States.  In  the 
same  year  the  question  of  river  pollution  was 
taken  up  by  the  Prussian  Government,  and 
the  Royal  Prussian  Testing  Institute  was 
founded  with  a  very  extensive  staff  and  equip- 
ment, to  collect  all  necessary  information  on 
which  the  action  of  authorities  could  be 
based.  Valuable  reports  are  issued  by  the 
Institute  from  time  to  time. 

A  similar  testing  station  has  been  estab- 
lished at  the  Pasteur  Institute  at  Lille,  under 
the  direction  of  Professor  Calmette,  and  very 
important  reports  have  been  published. 

The  Royal  Commission  on  Sewage  Disposal, 
appointed  in  England  in  1898,  has  from  the 
first  advocated  the  formation  of  a  central 
authority  to  deal  with  questions  of  water- 
supply  and  sewage  purification. 

Such  a  central  department  would  consist  of 
an  administrative  head,  assisted  by  highly 
qualified  bacteriological,  chemical,  and  engi- 
neering experts. 

Among  the  more  important  questions  which 
would  have  to  be  dealt  with  by  such  an 
authority  would  be  the  following : — 

1.  Disputes  between  local  authorities   and 
manufacturers  as  to  the  terms  and  conditions 
on  which  trade  effluents  should  be  admitted 
into  sewers. 

2.  The  control  of  shell-fish  layings. 

3.  The   protection  of   water  supplies  from 
pollution. 

4.  The  collection  of  information  as  to  the 
water  supplies  available  in  various  parts  of 
the  country. 

5.  The  collection  of  information  as  to  the 
need  of  water  in  various  parts  of  the  country. 

6.  The  settlement  of  standards  for  different 
reaches  of  water. 

7.  Conferring  powers  on  local  authorities, 
in  suitable  cases,  to  provide  separate  systems 
of  sewers  for  surface  water  and  to  enforce  the 
provision  of  separate  drains. 

8.  The  settlement  of   questions  as   to   the 


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extra  amount  of  sewage  which  a  local  autho- 
rity should  be  required  to  treat  during  storms. 
The  authority  would  also  undertake  special 
investigations  of  general  importance  and  col- 
lect and  collate  the  work  done  by  others,  for 
the  benefit  of  local  authorities  throughout  the 
country,  G.  J.  F. 

Rivers  Purification. — It  has  long  been 
recognised  that  the  prompt  removal  of  human 
excreta  from  the  vicinity  of  dwellings  is  one 
of  the  first  essentials  of  sanitation.  For  this 
reason  water-closets  were  introduced  in  1810, 
and  at  first  discharged  into  cesspools.  In 
early  days  sewers  were  largely  sewers  of 
deposit,  and  were  cleansed  at  intervals  by 
manual  labour.  It  was  afterwards  recognised 
that  discharge  into  a  river  outfall  was  pre- 
ferable to  methods  such  as  these.  With  the 
growth  of  population  and  the  increasing  pro- 
vision of  sewers,  serious  pollution  of  rivers 
occurred,  and  from  1848,  the  date  of  the  first 
Public  Health  Act,  to  the  present  day, 
numerous  Royal  Commissions  and  Select 
Committees  have  reported  on  the  best  methods 
of  preventing  the  pollution  of  rivers,  and  a 
number  of  Acts  have  been  passed  (see  references 
at  end  of  article).  All  the  Commissions  prior  to 
the  one  now  sitting,  which  was  appointed  in 
1898,  concurred  in  recommending  land  treat- 
ment in  one  form  or  another  as  the  most 
satisfactory  method  of  purifying  sewage  before 
discharge  into  a  stream.  This  method  was 
exemplified  in  the  case  of  the  Craigentinny 
meadows,  which  received  the  sewage  of 
Edinburgh  as  early  as  the  18th  century. 

Application  to  land  was  effected  either  with 
a  view  to  the  growing  of  crops,  by  the  method 
known  as  "  broad  irrigation,"  where  the 
sewage  was  applied  to  the  land  simultaneously 
with  the  growth  of  vegetables,  or  by  means  of 
"  intermittent  downward  filtration,"  a  method' 
introduced  by  Sir  Edward  Frankland  in  1870, 
in  the  First  Report  of  the  Royal  Commission  of 
1868.  By  this  method  the  sewage  is  run  on 
to  an  area  of  specially  prepared  land,  and 
allowed  to  filter  through,  a  further  dose  being 
applied  after  a  period  of  rest.  No  attempt  is 


necessarily  made  to  grow  crops,  and  the  land 
must  be  kept  open  by  ploughing.  More 
sewage  can  be  treated  on  a  given  area  by  this 
method  than  by  broad  irrigation ;  but  there 
is  no  essential  difference  in  principle  between 
the  two  methods, 

The  amount  which  can  be  dealt  with  by 
either  method  is  increased  by  preliminary 
removal  of  solid  matters,  either  by  simple 
settlement  in  tanks,  or  by  the  use  of  various 
chemicals  as  precipitants,  of  which  lime, 
either  alone  or  in  combination  with  salts  of 
iron  or  alumina,  is  chiefly  used.  The  results 
from  land  treatment  properly  carried  out  on 
suitable  land  were  so  good,  that  until  recently 
the  Local  Government  Board  refused  to  grant 
borrowing  powers  for  sewage  schemes,  even 
where  artificial  filters  were  provided,  unless 
provision  was  also  made  for  final  treatment 
on  land.  Owing  to  the  increasing  difficulty  of 
obtaining  such  land  in  the  neighbourhood  of 
large  centres  of  population,  great  attention 
has  been  given  during  the  past  twenty  years 
to  various  methods  of  treatment  by  artificial 
filters  of  various  descriptions. 

In  1898  a  Royal  Commission  was  appointed 
to  consider  the  whole  question,  and  has  issued 
numerous  reports.  It  was  able  in  its  first 
interim  report,  issued  in  1901,  to  give  the 
following  important  finding  : — 

"  We  are  satisfied  that  it  is  practicable  to 
produce  by  artificial  processes  alone,  either 
from  sewage,  or  from  certain  mixtures  of 
sewage  and  trade  refuse,  such,  for  example, 
as  are  met  with  at  Leeds  and  Manchester, 
effluents  which  will  not  putrefy,  which  would 
be  classed  as  good  according  to  ordinary 
chemical  standards,  and  which  might  be 
discharged  into  a  stream  without  fear  of 
creating  a  nuisance." 

Although  the  Commission  is  still  sitting, 
and  consequently  no  legislation  has  yet  taken 
place,  the  Local  Government  Board  have 
recently  granted  borrowing  powers  in  several 
cases  where  artificial  methods  have  been 
exclusively  employed,  without  having  recourse 
to  land. 

At  the  present  time  the  administration  of 


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the  Eiver  Pollution  Prevention  Acts  is  in  the 
hands  of  various  Conservancy  Boards,  e.g., 
the  Thames  and  Lea  Conservancy,  the  Mersey 
and  Irwell  Joint  Committee,  the  Rihble  Joint 
Committee,  the  West  Riding  Rivers  Board, 
and  Special  Committees  of  County  Councils. 
The  degree  of  purity  required  before  an  effluent 
is  allowed  to  enter  a  stream  is  somewhat 
differently  denned  by  these  various  bodies. 
Thus  the  "  limits  of  impurity "  allowed  by 
the  Mersey  and  Irwell  Joint  Committee  are 
1  grain  oxygen  absorbed  from  permanganate 
by  1  gallon  effluent,  0*1  grain  "albuminoid 
ammonia"  obtained  on  analysis,  per  1  gallon 
effluent ;  while  the  Ribble  Joint  Committee 
and  the  Derbyshire  County  Council  attach 
less  importance  to  the  "  oxygen  absorbed " 
figure,  and  more  to  the  presence  of  nitrates 
and  the  consumption  of  "  dissolved  "  oxygen 
by  the  effluent.  The  Thames  and  Lea  Con- 
servancy, on  the  other  hand,  having  to  safe- 
guard the  purity  of  the  Thames,  which  supplies 
a  portion  of  the  drinking  water  of  London, 
impose  more  exacting  standards. 

The  present  Royal  Commission  have  recom- 
mended a  central  authority  (see  above)  for 
the  control  of  the  purification  of  rivers  and  of 
water  supply  throughout  the  country.  This 
central  authority  would  act  in  conjunction 
with  the  present  Rivers  Boards  and  others 
likely  to  be  appointed.  They  suggest  that 
one  of  the  functions  of  such  an  authority 
would  be  to  formulate  standards  suitable  for 
differing  conditions.  They  recommend  that 
the  purity  of  an  effluent  should  mainly  be 
judged  by  the  suspended  matter  present,  and 
by  the  dissolved  oxygen  absorbed  under  denned 
conditions. 

Owing  to  the  fact  that  neither  nitration  by 
means  of  artificial  niters  nor  through  land 
can  be  relied  upon  to  produce,  under  all 
circumstances,  effluents  free  from  pathogenic 
organisms,  considerable  attention  has  recently 
been  given  to  the  possibility  of  sterilising 
effluents,  especially  when  they  have  to  enter 
streams  which  are  used  as  drinking  water 
supplies.  Although  it  has  been  found  possible, 
within  practicable  limits  of  cost,  chiefly  by 


the  use  of  chlorine  in  the  form  of  hypochlorites, 
or  oxides  of  chlorine  (obtained  by  electrolysis), 
to  sterilise  effluents  from  isolated  installations, 
such  as  hospitals,  or  even  under  some  circum- 
stances the  dry  weather  flow  of  town  sewage, 
the  difficulty  of  the  sterilisation  of  storm- 
water  has  so  far  proved  an  obstacle  to  the 
adoption  of  such  methods  on  the  large  scale. 

REFERENCES. — Reports  of  Royal  Commission 
on  Sewage  Disposal,  1901 — 8.  London: 
Wyman  &  Sons,  Ltd.,  109,  Fetter  Lane,  E.G. 

An  excellent  resume  of  the  progress  of  legis- 
lation on  River  Pollution  is  given  in  the 
evidence  of  Mr.  A.  D.  Adrian,  C.B.,  Assistant 
Secretary  to  the  Local  Government  Board. 
Royal  Commission,  Interim  Report,  Vol.  II., 
1902,  pp.  1—14. 

The  general  law  relating  to  sewage  disposal 
in  England  and  Wales  is  to  be  found  in  the 
Public  Health  Act,  1875,  supplemented  by  the 
Rivers  Pollution  Prevention  Acts  of  1876  and 
1893.  G.  J.  F. 

Roads,    Streets,    and    Pavements.  - 

General  Consideration — Location,  Gradients,  and 
Drainage — Width  of  Roads — Retaining  Walls— 
Embankments— Materials  and  Methods — Metal- 
ling— Repairs — Rolling— Paved  Carriageways- 
General  Method  of  Laying  Wood  Pavements- 
Asphalt  Pavements  —  Tar  Macadam  —  Brick 
Pavements — Paving  Setts  and  Blocks. 

GENERAL.  —  The  rapid  growth  of  traffic 
during  recent  years  calls  for  the  construction 
of  roadways  upon  the  soundest  and  most 
permanent  principles,  embodying  a  solid  and 
adequate  foundation,  good  subsoil  and  surface 
drainage,  together  with  a  sufficient  coating  of 
durable  road-metalling  suited  to  the  class  of 
traffic  to  be  accommodated. 

Many  of  the  highways  of  this  country, 
formed  in  earlier  years,  have  proved  to  be 
far  too  weak  and  inadequate  to  withstand  the 
demands  of  modern  conditions,  mainly  due  to 
the  absence  of  a  sufficiently  rigid  foundation 
and  to  the  employment  of  unsuitable  materials 
for  purposes  of  surface  repairs. 

The  practice  of  using  the  cheapest  stone 
obtainable  in  the  locality  cannot  be  defended 


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on  the  score  of  economy,  inasmuch  as  the  recent 
extended  employment  of  tougher  qualities  of 
metalling  has  heen  amply  justified  from  every 
point  of  view. 

In  some  cases  it  may  be  found  sufficient  to 
provide  a  top  coating  of  flints  or  granite  upon 
the  existing  natural  foundation,  especially 
where  the  traffic  is  light  and  where  the  bottom 
consists  of  chalk  or  solid  clay ;  but  with  the 
present  day  heavy  traffic  care  must  be  exer- 
cised to  insure  that  the  foundation  is  of  the 
best,  and  of  a  thoroughly  firm  nature.  Such 
a  substructure  is  essential  to  all  good  roads, 
and,  although  the  first  cost  may  be  heavy,  its 
provision  will  be  found  to  be  the  cheaper 
course  in  the  end. 

LOCATION,  GRADIENTS,  AND  DRAINAGE. — When 
new  roads  are  to  be  laid  out,  the  route  is 
generally  governed  by  existing  roads,  villages, 
and  towns.  In  all  cases  careful  surveys  should 
be  made  of  the  district  through  which  the  road 
is  to  be  constructed,  and,  where  practicable, 
t,he  route  for  the  road  should  be  one  with  the 
least  amount  of  hills,  provided  the  length  is 
not  unduly  increased  thereby.  When  making 
the  reconnaissance  the  work  will  be  simplified 
by  the  use  of  contour  maps  of  the  country 
traversed.  On  the  route-map  the  engineer 
should  note  the  available  materials  for 
embankments,  where  these  appear  necessary, 
the  nature  of  the  ground  to  be  passed  through, 
and  any  geological  peculiarities  on  or  near  the 
route  decided  upon,  with  conditions  in  favour 
of  or  against  the  particular  route  to  be  adopted, 
and  other  alternative  routes.  When  the  route 
has  finally  been  decided  upon,  stakes  should 
be  driven  into  the  ground  at  frequent  intervals 
along  the  centre  line.  Levels  should  then  be 
taken  longitudinally,  with  cross-sections  at 
all  necessary  points.  After  these  have  been 
plotted  the  finished  level  can  be  decided  upon, 
and  the  amount  of  excavation,  filling,  and 
banking,  can  then  be  ascertained. 

Roads  that  are  constructed  of  steep  gradients 
are  constantly  requiring  repairs,  these  being 
chiefly  due  to  the  erosion  caused  by  rains,  the 
abrasion  by  motor  tyres  in  ascending,  and  the 
use  of  skids  and  brakes  on  vehicles  descending 


hills,  which  cause  disintegration  of  the  surface. 
It  is  difficult  to  give  limits  to  the  permissible 
gradients,  as  so  much  depends  on  the  local 
circumstances  of  the  case,  and  the  materials 
used.  Several,  however,  have  been  given,  and 
we  may  consider  them  at  this  point.  Thomas 
Codrington  has  suggested  1  in  30  as  the  limit 
of  gradient  for  macadamised  roads.  Sir  John 
Macneil  was  of  opinion  that  no  road  ought 
to  exceed  a  gradient  of  1  in  40.  Sir  Henry 
Parnell  found  by  experiments  conducted  on 
the  Holyhead  road,  north  of  Coventry,  that  a 
gradient  of  1  in  35  should  not  be  exceeded. 
Where  roads  are  to  be  constructed  through 
hilly  districts,  long,  steep  inclines  should  be 
divided  up  as  far  as  possible  into  short  lengths, 
with  intervals  of  road  of  less  inclination.  This 
practice  is  especially  recommended  in  the 
case  of  curved  roads,  these  in  addition  being 
slightly  embanked  on  the  near  side  for  the 
safety  of  descending  traffic.  Short  lengths  of 
smaller  gradients  not  only  tend  to  reduce  the 
heavy  strain  upon  horses  drawing  loads  uphill, 
but  are  conducive  to  the  safety  of  fast-driven 
vehicles  and  other  traffic  when  descending, 
especially  where  the  road  has  concealed 
turnings. 

Perfectly  flat  roads  are  not  desirable,  as 
they  cannot  be  well  drained,  and  consequently 
remain  damp  for  long  periods,  thus  enhancing 
wear  and  tear,  and  gradual  deterioration  of 
the  metalling.  A  moderate  inclination  of, 
say,  1  in  150,  is  about  the  flattest  grade 
desirable,  so  as  to  enable  the  channel-wrater 
to  be  effectually  drained  away.  A  slight  gra- 
dient also  facilitates  the  draught  of  horses. 

Even  the  hardest  classes  of  metalling 
deteriorate  more  rapidly  when  constantly 
wet  and  damp,  and  for  this  reason  it  is  advis- 
able to  insure,  as  far  as  possible,  that  the 
road  should  be  open  to  the  moderate  action 
of  the  sun  and  wind.  When  traversing  undu- 
lating country,  the  road  should,  if  practicable, 
be  constructed  on  the  northern  side  of  the 
valleys,  and  it  is  found  that  all  obstructions, 
such  as  overhanging  trees,  high  walls  and 
fences  and  such  like,  are  detrimental  to  the 
durability  of  the  road. 


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It  is  not  to  be  assumed,  however,  that  it  is 
permissible  to  go  to  the  opposite  extreme,  and 
so  subject  a  roadway  to  excessive  exposure,  as 
very  strong  drying  winds  have  the  effect  of 


FIG.  l. 

removing  the  "  binding "  material  from  the 
surface,  and  thus  causing  the  roadway  to 
disintegrate  under  traffic. 

When  passing  through  hilly  country,  in 
laying  out  a  new  line  of  roadway,  it  often 
becomes  necessary,  in  order  to  find  the 
ground  over  which  the  ruling  gradients 
can  be  maintained  to  contour  the  hill- 
slopes,  to  cut  into  the  side  of  the  hill,  and 
to  embank  on  the  down- slope,  as  shown  in 
Fig.  1.  The  footpath  should  be  arranged 
on  the  outer  side,  in  order  that  the  heavier 
vehicular  traffic  may  be  carried  on  the 
natural  solid  ground.  Greater  stability  of 
that  portion  of  the  road  which  is  embanked 
on  the  outer  side  is  secured  by  "  stepping  " 
the  added  portion  as  shown,  which  tends  to 
prevent  slipping. 

All  springs   or   land   water   of  every  kind 


Roads   of    this    description    through    hilly 
country    often     involve     heavy     engineering 
works,    and    are    costly    to    construct,    but 
very  frequently  the  cost  is  materially  mini- 
mised by  the  fact  that  good  quality  stone  is 
obtainable  from  the  ground  traversed. 

Other    principal    classes    of    roads    are 
(1)  ordinary  country  main  roads;  (2)  country 
secondary  roads ;  (3)  roads  of  a  suburban 
and  residential  class ;  and  (4)    pitched   or 
paved   roads    of    busy   cities.      These   all 
require     special     types     of     construction, 
appropriate  to  each  individual  case,  some 
examples  of  which  are  given  in  Figs.  2 — 4. 
Country  main   roads    require    to    be    a 
minimum  of  about  21  ft.  in  width,  or  suffi- 
cient   for    three   vehicles    abreast,    with   two 
footpaths  of  6  ft.  width  each. 


should  be  properly  and  permanently  drained 
away  to  a  point  of  discharge  upon  the  solid 
ground,  well  below  the  outer  retaining  wall. 
Top-water  above  the  upper  wall  should 
be  intercepted  by  a  suitable  catchwater 
drain. 


FIG.  3. 

Suburban  and  residential  roads  are  com- 
monly 40  ft.  wide  overall,  having  two  footpaths 
of  9  ft.  width  each,  and  a  22  ft.  carriageway. 
The  trunk  or  main  arteries  through  largr 
towns  may  advantageously  be  60  ft.,  and 
in  special  cases  even  100  ft.  in  width,  so 
as    to    accommodate    ordinary    vehicular, 
tramway,  and  pedestrian  traffic. 

The    widening    of    important    roadways 
through  populated  centres  necessarily  be- 
comes a  very  costly  undertaking,  having 
regard  to  the  fact  that,  usually,  valuable 
properties  on  each  side  have  to  be  purchased, 
including  the  trade   interests  of  the  various 
premises  affected,  in   addition  to  which   the 
cost  of  the  structural    works   involved    have 
also  to  be  met. 

Under  some  circumstances,  particularly  in 


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districts  with  widely  varying  levels,  what  is 
known  as  "  hanging"  and  "double-hanging" 
roadways  have  to  be  formed.  Typical  roads 
of  this  class  are  shown  in  Figs.  5  and  6.  An 
important  point  in  all  such  cases  is  to  secure 
the  proper  removal  of  the  surface  water,  and 


FIG.  4. 

to  see  that  the  cross  gradients  are  suited  as 
near  as  possible  to  the  requirements  of  the 
traffic.      Sometimes  it   is   necessary,  in  im- 
portant cases,  that  a  full-sized  section    of 
this  cross  contour  should  be  built  up,  so 
that  the  effect  of  the  finished  road  surface 
can  be  properly  appreciated. 

It  is  argued  by  some  that  a  road  with 
a  concave  centre  is  preferable  to  the  common 
convex  form,  inasmuch  as,  it  is  suggested,  the 
centre  channel  divides  the  traffic  into  up  and 
down  lines,  one  line  of  channelling  and  street 
gullies  is  needed,  and  the  road-slop  and  water 
is  drawn  to  the  centre  of  the  road,  away  from 
the  footways,  thus  preventing  the  splashing 


The  thickness  should  be  carefully  calculated 
by  means  of  reliable  formulae  or  graphically, 
the  latter  being  the  more  expeditious  method. 
Sir  Benjamin  Baker  considered  that  the  thick- 
ness, in  average  ground,  should  be  one-third 
of  the  height  of  the  walls,  measured  from  the 
top  of  the  footings,  and  in  cases  where  the 
backing  and  foundations  are  both  favour- 
able a  wall  one-quarter  of  the  height   in 
thickness    similarly   measured,    having    a 
batter  of  1  in.  or  2  in.  per  foot  on  the  face 
will  be  sufficient.     Walls  with  a  slightly 
curved  face  in  vertical  section,  give  better 
results    and    are    more    effective    in    sup- 
porting the  thrust.     Th  esuccess  of  retaining 
walls  depends  largely  on  a  well-distributed  rigid 
foundation  and  upon  proper  drainage  at  the 


-.foorr/At  -- 


UP  AMP  oow/* 


AFf/c    o'r/oee  ar  //»/*•>»  sr/i/vaA/>ai 
FlG.   6. 


of  pedestrians  in  wet  weather.  Although  this 
form  of  road  may  possess  some  good  features 
from  certain  points  of  view,  it  must  be  remem- 
bered there  are  many  disadvantages,  and,  on 
the  whole,  the  balance  is  decidedly  in  favour 
of  the  ordinary  form  of  road,  except  in  certain 
special  circumstances. 

RETAINING  WALLS. — These  should  be  con- 
structed of  brick,  stone,  ordinary  and  rein- 
forced concrete,  and  be  of  sufficient  strength 
to  successfully  resist  the  thrust  from  behind. 


back.   Breast  walls  are  not  usually  built  to  resist 
pressure  from  behind,  but  merely  to  protect  the 
natural  earth  from  the  effects  of  the  weather. 
EMBANKMENTS. — There  are  many  ways  of 
constructing  these,  among  them  being  the 
tip-wa<jon  system.     This  is  an  expeditious 
method  of  carrying  out  the  work,  but  is 
somewhat   unreliable.      The   best  method 
appears  to  be  that  in  which  the   work  is 
built  up  in    successive  layers  or  courses, 
each    layer    being    concave    in   form   and 
thoroughly  consolidated  as  the  work  proceeds. 
Stability  will  thus  be  obtained  for  the  whole 
structure,  and  especially  is  this  the  case  when 
embankments   are   formed    with    slopes   con- 
sisting of  material  resting  at  its  natural  angle 
of  repose.      The  angle  of  repose  of  different 
materials  in  the  table  on  page  368. 

For  embankments  and  cuttings  exceeding 
4  ft.  in  depth,  Sir  H.  Parnell  has  recommended 
a  slope  of  3  ft.  horizontal  to  1  ft.  perpendicular. 
For  cuttings  in  chalk  or  marl  a  slope  of  one  to 


367 


ROA 


ENCYCLOPAEDIA   OF 


ROA 


one  will  be  sufficient ;  in  solid,  hard,  and  uni-     possible.      The    subsoil    water     from    rising 


form  sandstone  slopes  of  one-quarter  to  one 
will  suffice.  Where  the  sandstone  stratum  is 
in  alternate  layers  with  clay  or  marl,  the  stone 
becomes  detached  and  will  slip,  and  for  that 
reason  hard  and  fast  rules  are  difficult  to  give. 


NATURAL  SLOPES  OF  EARTH 
LINE). 


(WITH  HORIZONTAL 


Earth. 

Angle  of 
Repose. 

Coefficient 
of 
Friction. 

Customary 
Designation  of 
Natural  Slope. 

Dry     sand,     clay, 

From 

(  0-75 

(  1-33  to  1 

and  mixed  earth 

30°  to  21° 

(0-38 

(  2-63  to  1 

Damp  clay 

45° 

1-00 

1  to  1 

Wet  clay 

From 

(0-31 

(3-23  to  1 

17°  to  14° 

(  0-25 

(  4-0    to  1 

Shingle  and  gravel 

From 

(  I'll 

0-9    to  1 

48°  to  35° 

I  0-70 

1-43  to  1 

Peat 

From 

(  1-00 

1       to  1 

45°  to  14° 

(0-25 

4       to  1 

FIG.  7.— Drainage. 

Slopes  should  be  finished  with  a  suitable 
material  for  grass  growing,  or,  in  cases  where 
there  is  an  excessive  amount  of  water,  with 
ballast. 

DRAINAGE. — Care  must  be  exercised  in  the 
formation  of  embankments,  cuttings,  "and 
roads  generally,  to  insure  an  efficient  system 
of  subsoil  and  surface  drainage,  as  the 
stability  of  these  works  depends  largely  on 
their  foundations  being  kept  as  dry  as 


ground    should    be    intercepted    and    carried 
away  in  the  manner  shown  in  Fig.  TA.     Tins 
intercepted  water  can  either  be  carried  along 
the  catch-water  drain  to  the  low-lying  ground. 
or  in  a  pipe  drain  down  the  slope,  discharging 
at  frequent  intervals  into  the  side  channel  of 
the  road  or  into  a  covered  drain.     Land  water 
drains  can  be  either  open  roadside  trenches 
constructed   beyond   the    fences,   or    covered 
soaking   drains,  as  shown   in  Fig.   TB.     The 
latter  are   to  be  recommended,  and  may  be 
formed  of    land  pipes  laid  in  the  ditch   and 
covered  with  large  stones  up  to  the  level  of 
the  surface  in  the  following   manner : — The 
bottom    of   the   trench  is  covered  with  hurd 
material  upon  which  is  laid  the  open-jointed 
pipes.     These  are  covered  with  large  stones 
about  6   in.  in  diameter  at   the  bottom  and 
gradually  reduced  in  size  to- 
ward the  top.     The  box-drain 
C  and  D  (Fig.  7)  is  usually 
adopted     in    districts    where 
stone  is  plentiful,   the   stone 
"bolt"    taking   the    place    of 
the  drain  pipes.    Cross  drains 
should   be   laid   at   distances 
varying  from  25  ft.  to  50  ft., 
according  to  the  nature  of  the 
subsoil,  and  be  connected  to 
the  covered  drains  in  the  sides, 
ditches,  or  trenches.     In  ordi- 
nary   town    macadam    roads 
subsoil      drains     are     rarely 
necessary,  but  when  occasion 
arises    they   should    be    laid 
down  the  centre  of  the  road 
parallel  to  its  direction  and 
connected  to  the  surface  water  sewer.     Water 
is  carried  off  the  surface  of  the  road  by  form- 
ing its  cross  section  to  a  slight  camber.     This 
will  vary  according  to  the  material  used,  the 
following  being  found  serviceable  ratios  : — 
Macadam  roads  1  in  30  to  1  in  40. 
Wood  paving    .  1  in  45. 
Asphalte.     .     .  1  in  55. 
The  water   thus  removed  is  conducted  to 
channels  formed  at  the  sides  of  the  roads  and 


368 


ROA 


MUNICIPAL   AND    SANITAKY   ENGINEERING. 


ROA 


is  caught  in  catch-pits  or  gullies  provided  at 
frequent  intervals  varying  from  80  ft.  to  120  ft. 
according  to  the  gradient.  These  pits  and 
gullies  are  connected  to  the  surface  water  sewer 
or  covered  ditch  drain  as  the  case  may  be.  In 
order  to  provide  a  sill  between  the  footpath  and 
water  channel  a  kerb  is  laid  longitudinally 
along  the  road  at  a  height  of  from  3  in.  to 
7  in.  from  the  channel  and  the  footpath  is 
finished  level  with  its  upper  surface.  The 
materials  used  for  such  kerbing  are  either 
granite,  stone,  or  iron.  Granite  and  iron  are 
the  best  materials  for  roads  with  heavy  traffic, 
and  for  roads  with  light  traffic  sandstones, 
Kentish  ragstone,  cement  concrete,  or  petrified 
fireclay  block  will  be  found  suitable.  The  sizes 
used  are  usually  as  follows : — 12  in.  by  8  in. 
laid  flat,  slightly  tilted  towards  the  road  ;  6  in. 
by  12  in.  laid  on  edge ;  4  in.  by  9  in.  laid  on  edge. 
The  lengths  should  not  be  less  than  3  ft.  The 
top  surface  and  front  face  of  stone  kerbs  should 
be  hammer  dressed,  the  back  being  dressed  to 
a  depth  of  3  in.  from  the  top.  All  ends  should 
be  dressed  at  least  6  in.  from  the  top,  to  give 
close  joints,  and  overflows  should  be  cut  in 
the  kerb  over  each  gully  or  catch-pit.  The 
bed  should  be  formed  of  6  in.  of  cement  con- 
crete extending  beyond  the  back  face  to  a  dis- 
tance of  2  in.  Channels  may  be  constructed  of 
granite  in  the  form  of  lengths  of  kerb  or  setts 
of  varying  sizes,  the  beds  being  of  concrete 
similar  to  that  for  the  kerb,  and  extending 
beyond  the  face  to  a  distance  of  3  in. 

MATERIALS  AND  METHODS  EMPLOYED  IN 
BROKEN  STONE  ROADS. — Before  treating  of  the 
covering  or  road  surface  the  formation  of  the 
foundation  must  be  dealt  with.  After  the  line 
of  road  has  been  excavated  and  shaped  to  the 
desired  contour,  material  of  various  kinds  is 
laid  upon  the  surface  to  form  the  hardcore 
foundation.  This  consists  either  of  (1)  boulders 
or  large  stones  laid  "hand  pitched,"  the  stones 
being  about  9  in.  in  depth,  and,  as  a  cover- 
ing and  also  to  fill  in  the  interstices,  a  layer 
of  smaller  stones  about  3  in.  in  diameter  is 
then  spread,  and  the  whole  well  rolled  solid ; 
or  (2)  hardcore  consisting  of  broken  bricks, 
stone,  clinker,  or  other  similar  material  spread 


in  layers,  each  layer  being  well  rolled,  the  total 
depth  of  material  varying  from  9  in.  to  15  in. 
according  to  the  traffic  the  road  will  have  to 
withstand. 

Upon  the  foundation  is  spread  the  top  sur- 
face coating,  formed  with  such  materials  as 
the  engineer  has  proved  by  experience  to  be 
the  best.  When  deciding  this,  many  points 
must  be  kept  in  view  as  to  the  requirements 
of  a  good  carriageway,  and  among  them  are 
the  following : — 

1.  The  cost  of  construction  and  maintenance 
must  be  economical. 

2.  The  material  used  must  be  durable  and 
as  noiseless  as  possible. 

3.  It  must  be  firm  and  hard,  and  safe  for 
horses,  giving  them  a  good  foothold. 

4.  It  must  be  sanitary,  and  as  free  from 
mud  and  dust  as  possible. 

5.  It  must  be  impervious  to  moisture  and 
impurities    of    every    kind,    and    be     easily 
cleansed. 

6.  It   must   be   easily  taken   up   and   laid 
down  again  when  required,  after  being  broken 
up  for  gas,  water,  electric  light,  drains,  and 
other  trenches. 

7.  When  used  for  a  tramway  the  material  laid 
down  alongside  the  rails  must  be  capable  of  with- 
standing the  wear  caused  by  the  wheel  flanges. 

Major  Isaacs,  in  a  paper  read  before  theRoyal 
Society  of  Arts  on  the  merits  and  demerits  of 
road-making  materials,  compiled  the  following 
table  from  experiments  bearing  upon  the  above 
points,  showing,  in  order  of  merit,  the  results 
of  the  different  materials  used. 


First. 

Second. 

Third. 

Public  hygiene    .  . 

Asphalte 

Granite 

Wood 

Noiselessness 

Wood 

Asphalte 

Granite 

Safety  for  horses  \ 

under  existing  > 

Wood 

Asphalte 

Granite 

conditions 

Cleansing 

Asphalte 

Granite 

Wood 

Durability 

Granite 

Asphalte 

Wood 

Economy 

Granite 

Wood 

Asphalte 

Facility  of  repairs 

Asphalte 

Wood 

Granite 

Facility  for  tram-  ) 
ways     .  .             ) 

Granite 

Wood 

Asphalte 

Broken  stone  roads  continue  to  be  in  good 


M.S.E. 


369 


B  B 


ROA 


ENCYCLOPEDIA   OF 


ROA 


favour,  and  when  the  materials  used  have  been 
carefully  selected  and  properly  laid,  they  can 
be  adopted  with  economy  on  country  and 
other  roads  subjected  to  medium  and  light 
traffic.  They  are,  however,  open  to  objections 
from  a  sanitary  point  of  view,  and  constitute 
one  of  the  chief  difficulties  in  the  dust  pro- 
blem. These  objections  have  been  dealt  with 
in  the  article  on  "  DUST  PREVENTION." 

MATERIALS. — The  materials  used  in  forming 
macadam  roads  should  be  tough  and  of  uniform 
hardness  and  durability.  Brittle  stones  do 
not  wear  well  and  rapidly  grind  away  into 
dust.  Atmospheric  influences  affect  many 
descriptions  of  stone,  and  care  must  be  taken 
to  choose  one  that  will  satisfy  all  the  above 
conditions.  To  ascertain  the  wearing  and 
other  qualities  of  stone,  trials  should  be 
made  by  laying  lengths  of  different  classes 
of  stone  in  streets  subjected  to  the  same 
amount*  of  traffic.  The  results  can  then  be 
compared,  and  will  include  not  only  the 
result  of  the  effect  of  the  traffic  on  the  stones, 
but  also  the  effect  of  the  weather  and  atmo- 
spheric influences  and  the  binding  properties 
of  each.  It  has  been  found  that  moderately 
hard  and  tough  stones  are  better  than  exces- 
sively hard  stones  for  binding  purposes.  The 
engineers  of  the  French  Ponts  et  Chaussees 
have  endeavoured  to  arrive  at  a  comparative 
numerical  value  of  the  qualities  of  materials 
used  on  the  national  roads,  and  the  coefficients 
of  quality  for  the  various  materials  are  given 
as  follows  : — 


Coefficient  for 
Wear. 

Coefficient  for 
Working. 

Basalt 

12-5  to  24-2 

12-1  to  16-00 

Porphyry 

14-1  to  22-9 

8-5  to  16-3 

Gneiss 

10-3  to  19 

13-4  to  14-8 

Granite 

7-3  to  18 

7-7  to  15-8 

Syenite 

11-6  to  12-7 

12-4  to  13-00 

Slag       

14-5  to  15-3 

7-2  to  11-1 

Quartzite 

13-8  to  30 

12-2  to  21-6 

Quartz  Ore  Sandstone 

14-3  to  26-2 

9-9  to  16-6 

Quartz 

12-9  to  17-8 

12-3  to  13-2 

Silex 

9-8  to  21-3 

14-2  to  17-6 

Chalk  Flint      .  . 

3-5  to  16-8 

17-8  to  25-5 

Limestone 

6-6  to  15-7 

6-5  to  13-5 

The  coefficient  20  is  equal  to  excellent,  10 


to  sufficiently  good,  and  5  to  bad.  Space  will 
not  admit  of  a  full  geological  description  of 
the  formations  from  which  these  various  rocks 
are  obtained,  but  the  reader  is  referred  to 
geological  books  and  survey  maps  from  which 
the  information  can  be  obtained.  The  majority 
of  road  stones  contain  from  45  to  70  %  o  f 
silica,  and  have  a  specific  gravity  varying  from 
2'50  to  29'5.  A  few  of  the  best  stones  in  use 
will  now  be  briefly  referred  to. 

BASALT. — This  stone  when  obtained  from 
the  best  quarries  appears  to  withstand  the 
wear  of  traffic  better  than  many  other  classes. 
The  Glee  Hill  basalt  quarries  in  Shropshire 
produce  one  of  the  best  road  stones  on  the 
market.  Owing  to  the  great  distance  of  the 
quarry  from  the  coast  and  high  rates  for 
freightage,  the  price  is  prohibitive  in  some  parts 
of  the  country,  but  where  possible  the  stone 
may  be  used  with  great  success,  and  though  the 
first  cost  is  sometimes  heavy,  a  corresponding 
sum  is  saved  in  repairs  and  maintenance.  This 
stone  is  hard  and  tough,  and  its  peculiar  con- 
struction makes  it  a  good  material  for  macadam, 
and  it  is  comparatively  free  from  dust. 

GUERNSEY  GRANITE. — This  is  a  durable 
material  but  has  a  tendency  to  wear  unevenly. 
It  should  not  be  used  in  hilly  districts  as  it 
becomes  rather  slippery,  but  by  carefully  select- 
ing the  best  blue  stone  success  maybe  obtained. 

ST.  KEVERNE. — This  stone  is  exported  from 
West  Cornwall,  and  consists  of  a  basaltic  trap 
rock.  It  wears  uniformly,  and  ranks  as  a 
good  road  stone. 

OTHER  QUARRIES. — There  are  man}^  other 
quarries,  too  numerous  to  mention,  from  which 
excellent  stone  may  be  obtained,  notably  those 
in  Leicestershire  and  Derbyshire. 

Before  adopting  a  new  class  of  stone  of 
which  no  local  experience  is  available  proper 
tests  should  be  carried  out,  as  the  value  of  a 
road  stone  lies  in  its  power  to  withstand  the 
peculiar  conditions  and  traffic  of  the  district. 

Haulage  of  stone  on  to  the  roads  is  an 
expensive  item,  and  in  many  circumstances 
motor  haulage  will  be  found  much  cheaper 
and  quicker  than  haulage  by  team  labour. 

METALLING.  -  -  The     depth     of     metalling 


370 


ROA 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


ROA 


required  varies  according  to  local  circum- 
stances and  the  character  of  traffic.  Opinions 
differ  as  to  the  size  of  the  stones  to  be  used, 
but  those  ranging  from  1^  in.  to  2J  in.  in  dia- 
meter are  usually  employed.  Some  engineers 
prefer  to  use  small  stones  and  allow  them  to 
bind  themselves  together  on  being  rolled ; 
others  prefer  to  use  larger  sized  stones  and 
use  the  "  siftings  "  therefrom  for  "  binding." 
A  sandy  material  such  as  hoggin  is  also  some- 
times used.  Stone,  when  properly  riddled 
through  a  stone-breaker,  contains  45  %  of 
space  previous  to  rolling,  and  after  rolling 
interstices  to  the  extent  of  20  %  still  remain, 
so  that  the  use  of  a  binder  is  necessary. 

Some  engineers  use  road  mud  and  worn 
surface  material  as  a  binding  for  road  metal- 
ling, but  the  practice  is  a  bad  one  and  causes 
a  heavy,  greasy,  and  dangerous  mud  to  be 
formed  on  the  surface  in  wet  weather,  and 
a  vast  amount  of  dust  in  dry  weather,  thus 
increasing  the  cost  of  scavenging,  watering, 
and  maintenance.  Siftings  or  hoggin  make 
good  binding  materials,  always  look  clean,  and 
produce  a  minimum  of  dust  and  mud.  It  is 
false  economy  to  use  a  cheap  and  soft  "  bind- 
ing," as  it  increases  the  cost  of  scavenging, 
causes  the  road  to  disintegrate  more  rapidly, 
and  adds  to  the  dust  nuisance. 

The  macadam  should  be  laid  to  a  total  depth 
of  6  in.  before  rolling,  the  finished  thickness 
being  about  4  in.  The  stones  should  be  evenly 
spread  in  two  layers  and  rolled  and  watered  to 
the  required  thickness.  '  The  first  rolling  should 
be  on  the  dry  metal,  and  after  it  has  partly 
consolidated  it  may  be  watered.  In  some  dis- 
tricts engineers  use  a  top  covering  of  granite 
and  gravel  or  granite  and  flints,  the  layer 
of  gravel  or  flints  being  4  in.  in  thickness  and 
the  layer  of  granite  being  2  in.  in  thickness, 
both  layers  being  watered  and  rolled  to  a  total 
depth  of  6  in.  It  has  given  good  results 
and  can  be  constructed  at  less  cost  than  a 
road  surface  having  a  consolidated  thickness 
of  4  in.  of  granite.  The  cost  of  macadam 
roads  varies  according  to  local  conditions,  but 
the  following  table  of  the  cost  in  a  London 
district  may^prove  useful. 


2  in.  of  Guernsey 

2  in.  of  Enderby 

Granite  on  4  in. 

Granite  on  4  in. 

of  Local  Flints. 

of  Local  Flints. 

s.       d. 

s.       d. 

Cost  per  cubic  yard 

16     0 

13     6 

Unloading 

0      4Jr 

0     4| 

Loading     . 

0     3" 

0     3 

Haulage 

0  10 

0  10 

Cost   per  cubic  yard   on 

road,  say, 

17     6 

15     0 

Cost  per  super,  yard  3  in. 

thick  on  road 

1     5J 

1     3 

Flints,    local,    6s.    cubic 

yard  on  road,  4  in.  (6  in. 

before  rolling),  cost  per 

super,  yard 

1     0 

1     0 

Cost  of  material  6  in.  in 

thickness   when  rolled 

2     5i 

2     3 

Spreading  and  rolling     .  . 

0     3" 

0     3 

Total  cost  per  super,  yard 


2     6 


To  this  cost  must  be  added  that  of  the 
foundation  and  excavation,  and  the  total  works 
out  at  from  4s.  GiL  to  6s.  per  superficial 
yard. 

REPAIRS. — It  is  usually  desirable  to  loosen 
the  top  surface  of  the  old  materials  on  roads 
previous  to  applying  the  new  stones.  The 
bed  is  then  formed  to  the  desired  contour,  and 
some  of  the  old  material  after  screening  may 
be  used  in  conjunction  with  the  new  for  the 
repairs.  Hand  picking  is  largely  resorted 
to,  the  road  surface  being  broken  across  at 
frequent  intervals  with  grading  picks  vary- 
ing from  6  Ibs.  to  9  Ibs.  in  weight.  The 
repairs  on  inclines  should  be  commenced 
at  the  foot  and  worked  up  the  hill.  Hand 
picking  costs  about  l%d.  per  superficial 
yard.  The  whole  of  the  surface  should  be 
equally  broken  and  reformed.  If  the  sur- 
face has  worn  hollow,  total  picking  up  of 
the  road  may  be  undesirable,  and  after  a 
good  watering  or  in  wet  weather  the  new 
material  may  be  put  straight  on  to  the  old 
surface  to  the  required  thickness  and  con- 
tour, and  to  bind  it  well  into  the  old  road 
it  will  only  be  necessary  to  pick  up  the  road 


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along  the  edge  of  the  water  channel  for  a 
width  of  about  1'2  or  18  in.  Many 
scarifiers  have  of  recent  years  been  intro- 
duced by  which  the  road  surface  may  be 
broken  by  machinery.  These  machines  pick 
up  the  whole  or  any  portion  of  a  macadamised 
road  surface  where  required  with  rapidity 
and  economy.  Messrs.  Aveling  &  Porter's 
"  Morrison  "  scarifier  is  often  attached  to  a 
steam  road  roller,  and  can  be  put  in  and  out 
of  operation  at  will,  and  worked  either  back- 
wards or  forwards.  Eutty's  scarifier  is  another 
good  appliance.  This  consists  of  a  heavy 
cast-iron  frame,  into  which  are  fixed  six 
movable  steel  tines,  or  teeth,  three  at  each 
end,  one  set  being  used  at  a  time,  according 
to  the  direction  in  which  the  engine  is  moving. 


engine  will  have  to  be  constantly  reversed, 
which  entails  excessive  wear.  Statistics  have 
been  published  as  to  the  superficial  area  and 
relative  cost  of  rolling  work  done  in  a  specified 
time,  but  the  results  vary  widely. 

A  record  has  been  made  of  each  day's  work 
in  Penzance  in  order  to  arrive  at  the  average 
cost  of  the  rolling  done.  The  quantity  of 
material  laid  and  the  superficial  area  rolled 
were  booked  at  the  end  of  each  day,  with  the 
result  that  a  good  day's  work  in  thoroughly 
consolidating  town  roads,  subject  to  the  inter- 
ference of  traffic,  &c.,  was  found  to  be  450  to 
500  superficial  yards  of  material  consolidated, 
the  cost  averaging  from  $d.  to  Id.  per  yard 
superficial,  or  5^d.  to  Id.  per  ton  of  road 
stone,  the  calculation  including  wages,  coal, 


FIG.  8. — Cross  Section  of  a  Macadam  Eoadway  coated  with  3  in.  of  Flints  and  3  in.  of  Granite. 

The  machine  is  drawn  along  by  the   steam     oil,    waste,    brooms,    team    work,    watering, 


roller,  to  which  it  is  connected  by  a  chain, 
which  relieves  the  engine  of  the  vibration 
inseparable  to  the  work  of  scarifying.  Other 
scarifiers  in  use  are  Jackson's  scarifier, 
Yoysey's  &  Hosack's  scarifier,  Wallis  Road- 
Pecking  Machine,  Fowler's  "  Evershed  "  scari- 
fier, and  W.  Thackeray  &  Son's  machine. 
There  is  a  saving  of  from  35%  to  50%  by  the 
use  of  a  scarifier  as  compared  with  the  cost  of 
hand  picking.  In  an  experiment  carried  out 
with  a  Ptutty's  scarifier  it  was  ascertained 
that,  after  paying  all  expenses  and  providing 
for  wear  and  tear  of  machinery,  the  total  cost 
averaged  at  the  end  of  one  week's  work  rather 
under  \d.  per  yard  superficial  of  work  done. 
PiOLLiNG. — This  is  a  necessary  part  of  the 
work  in  road  making  and  repair,  as  it  econo- 
mises both  time  and  material.  In  consolidat- 
ing road  metalling  it  is  a  great  mistake  to  use 
too  much  water — only  a  small  quantity  is 
required  by  an  experienced  driver.  The  road 
should  not  be  rolled  in  short  lengths,  as  the 


depreciation  of  steam  roller  and  plant.  .But 
the  average  cost  for  the  whole  period  in  patch- 
ing and  general  work,  including  time  lost,  was 
nearly  double. 

PAVED  CARRIAGEWAYS. — Paved  carriageways 
are  of  two  descriptions,  viz.,  those  which  are 
laid  with  transverse  joints  from  kerb  to  kerb, 
such  as  wood  blocks,  granite  setts,  bricks,  &c., 
and  those  which  are  free  from  joints,  such  as 
asphalte,  tar,  macadam,  &c.  The  use  of  wood 
for  street  paving  purposes  has  become  general 
in  this  and  other  countries  of  recent  years. 
Soft  wood  pavements,  which  are  so  called  to 
distinguish  them  from  the  harder  and  denser 
woods  of  Western  Australia,  have  been  favoured 
by  some  authorities  on  account  of  their  com- 
bined qualities  of  noiselessness  and  compara- 
tively low  initial  cost  of  construction.  The 
drawback  to  the  employment  of  soft  wood, 
however,  is  its  short  life  as  compared  with 
the  hard  woods.  Since  the  advent  of  wood 
pavements  many  endeavours  have  been  made  to 


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produce  a  material  by  chemical  or  other  means 
which  will  increase  the  life  of  various  soft 
woods  and  render  them  more  durable  and  sani- 
tary for  street  paving.  The  methods  adopted 
have  to  a  great  extent  met  with  success, 
so  much  so  that  the  softer  description  of  woods 
so  prepared  have  become  iirore  extensively  used. 
Some  of  tlie  processes  by  which  the  wood  is 
treated  may  be  briefly  explained.  '' Creosot- 
ing"  consists  of  subjecting  the  wood  to  immer- 
sion in  the  oil  known  as  creosote,  which  soaks 
into  the  pores  of  the  wood,  serving  both  to  keep 
out  the  atmospheric  influences  and  to  check 
decomposition.  Creosote  is  sometimes  forced 
into  the  wood  under  pressure  so  as  to  impreg- 
nate the  timber  to  as  large  a  degree  as  possible. 
For  this  purpose  the  blocks  are  placed  in  an 
iron  boiler  containing  boiling  creosote  oil ; 
the  boiler  is  then  closed  and  an  internal  pres- 
sure of  130  Ibs.  to  the  square  inch  is  applied 
to  force  the  oil  into  the  wood,  each  cubic  foot 
of  wood  absorbing  from  8  Ibs.  to  10  Ibs.  of 
oil.  It  appears  that  when  blocks  are  so  treated 
under  pressure  the  wood  is  often  damaged  and 
its  life  reduced — the  fibre  and  pores  of  the 
wood  being  injured  thereby;  at  any  rate  the 
resulting  wear  will  not  warrant  the  extra  cost 
incurred.  The  great  point  to  be  observed  in 
all  soft  wood  paving  blocks  is  to  insure  them 
being  well  seasoned  previous  to  their  being 
creosoted.  They  must  be  free  from  sap,  or 
the  creosoting  will  be  the  very  means  of 
defeating  the  object  for  which  it  is  used. 
Instead  of  preventing  decay  the  creosoting 
will  cause  rapid  fermentation  in  the  heart  of 
the  wood,  and  will  within  a  comparatively 
short  period  produce  rapid  deterioration  and 
rot.  It  is  useless  to  attempt  to  season  the 
blocks  after  the  process  is  applied.  This 
precaution  should  be  taken  in  every  case 
where  any  preservatives  are  resorted  to. 
Burnett's  process  consists  of  a  solution  of 
chloride  of  zinc  and  water  in  the  proportion 
of  1  of  chloride  of  zinc  to  45  parts  water. 
This  solution  is  forced  into  the  wood  under  a 
pressure  of  130  Ibs.  to  the  square  inch,  or,  as 
in  the  case  of  creosoting,  it  can  be  applied  by 
immersion  for  a  lengthy  time.  Chloride  of 


zinc  renders  the  wood  incombustible.  Gar- 
dener's process  is  employed  with  the  intention 
of  dissolving  the  sap  and  driving  out  the 
moisture  from  wood  by  means  of  chemicals, 
leaving  the  fibre  only  to  remain.  On  com- 
pletion of  this  process  other  chemicals  are 
employed  to  render  the  wood  more  durable 
and  incombustible.  Ryan's  process  is  a  solu- 
tion of  corrosive  sublimate,  or  bichloride  of 
mercury  and  water.  The  timber  is  immersed 
for  a  period  of  about  30  hours  for  each  inch 
in  thickness  for  soft  wood  paving  blocks.  The 
solution  is  made  in  the  proportion  of  1  of  bi- 
chloride of  mercury  to  130  to  150  gallons  of 
water.  This  process  increases  the  density  of 
the  wood  and  retards  dry  rot  in  seasoned  wood. 
In  1839  the  first  wood  pavement  was  laid  in 
London  on  the  Stead's  system,  in  front  of 
the  Old  Bailey.  Half  a  century  later,  in 
1889,  the  first  hard  wood  pavement  was 
laid  in  Westminster  Bridge  Road.  Some  of 
the  best  known  systems  of  wood  pavements 
are : — 

ASPHALTIC  WOOD  PAVING. — This  consists  of 
a  concrete  foundation  covered  with  a  layer 
of  mastic  asphalte  \  in.  in  thickness,  on  which 
creosoted  wood  pavement  blocks  are  placed, 
with  about  ^  in.  spaces  between  each  row. 
These  spaces  or  joints  -are  then  partly  run  in 
with  melted  asphalte,  which  readily  unites 
with  the  similar  material  previously  laid  over 
the  foundation.  The  remaining  portion  of 
the  joints  is  then  filled  in  with  cement  grout 
or  lias  lime. 

HENSON'S  WOOD  PAVEMENT. — In  this  system 
the  paving  blocks  are  laid  on  a  concrete  foun- 
dation covered  with  well-tarred  roofing  felt,  a 
strip  of  which  is  also  placed  between  every 
other  course  of  blocks  while  being  laid.  The 
courses  are  driven  closely  together  with  heavy 
sledge  hammers,  a  plank  being  previously 
placed  against  the  blocks.  The  work  is  grouted 
in  with  pitch.  This  road  is  supposed  to  be 
rendered  as  noiseless  as  possible  by  the 
elasticity  of  the  tarred  felt. 

HARBISON'S  WOOD  PAVEMENT  differs  from 
the  asphalte  wood  paving  in  one  respect  only. 
Instead  of  the  under  laying  of  mastic  asphalte, 


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the  blocks  are  raised  about  \  in.  from  the 
foundation  on  strips  of  wood,  and  hot  asphalte 
is  then  run  through  the  joints  until  the  space 
between  the  concrete  foundation  and  the  wood 
pavement,  and  also  the  joints,  are  all  filled  in 
one  process. 

IMPROVED  WOOD  PAVEMENT. — The  Improved 
Wood  Pavement  Company  originally  laid  wood 
blocks  on  two  thicknesses  of  1  in.  tarred 
boards,  laid  so  as  to  cross  over  each  other  at 
right  angles,  and  which  formed  the  only 
foundation  over  the  ordinary  road  bed.  The 
improved  road  system  consists  of  the  follow- 
ing :  —  Upon  a  foundation  constructed  of 
6  in.  of  Portland  cement  concrete,  faced  over 
with  f  in.  thickness  of  cement  mortar  to  the 
camber  required  for  the  pavement  when 
finished,  a  covering  of  creosoted  red  Northern 
fir  blocks,  each  measuring  8f  in.  long,  3£  in. 
wide,  and  6  in.  deep,  is  laid.  The  blocks  are 
set  with  close  longitudinal  joints  and  f  in. 
transverse  joints,  the  spaces  between  the  blocks 
being  regulated  by  the  temporary  insertion  of 
strips  of  wood,  which  are  afterwards  removed. 
Hot  pitch  is  then  run  into  the  open  spaces, 
which  fills  any  irregularities  existing  between 
the  foundation  and  the  wood  covering  and 
also  partially  fills  the  joints.  The  joints  are 
finished  with  a  grouting  of  neat  cement, 
broomed  over  the  surface  until  it  is  rendered 
as  impermeable  as  possible.  A  coating  of 
fine  gravel  is,  on  completion,  thrown  over 
the  surface,  to  be  forced  into  the  face  of  the 
wood  by  the  weight  of  the  traffic.  The  gravel 
which  is  spread  over  the  face  of  the  work 
wears  into  the  wood,  forming  a  hard  crust 
and  indurating  the  wearing  surface  of  the 
pavement. 

DUFFY'S  DOWELLED  PAVEMENT. — This  pave- 
ment is  laid  on  a  foundation  of  concrete  or 
other  material  of  the  thickness  required.  The 
blocks  are  bound  together  by  dowels  inserted 
into  recesses  on  each  side  of  the  block.  This 
system  provides  for  the  weight  of  the  traffic 
to  be  spread  over  a  wide  area,  and,  therefore, 
there  is  less  need  of  heavy  foundation  works. 
The  thickness  of  the  blocks  can  also  be  reduced. 
It  is  particularly  well  adapied  to  swing  and 


other  opening  bridges  and  for  street  paving 
generally. 

There  are  many  other  systems  of  wood 
paving  invented,  with  interlocking  joints, 
elastic  foundations,  grooves  at  the  sides  and 
grooves  in  the  surface,  but  in  practice  it  is 
found  that  complications  of  construction 
militate  against  general  success,  besides 
adding  to  the  cost  of  the  work. 

GENERAL  CONSTRUCTION  OF  WOOD  PAVE- 
MENTS.— Wood  blocks  are  usually  made  9  in. 
long,  3  in.  wide,  and  4^  in.  deep,  but  some 
are  used  5  in.  to  6  in.  deep.  The  only  real 
advantage  to  be  derived  from  the  use  of  the 
deeper  blocks  is  that  when  one  side  is  worn 
uneven  the  blocks  can  be  reversed  and  used 
again.  When  the  blocks  are  reversed  with 
the  worn  side  turned  against  the  concrete 
foundation,  it  is  necessary  to  adopt  some 
system  for  levelling  up  the  surface,  such  as  a 
bed  of  mortar  or  sand  about  f  in.  deep.  In 
the  eastern  colonies  a  large  quantity  of  wood 
paving  has  been  carried  out  with  blocks  of 
7  in.  and  8  in.  long,  and  blocks  of  6  in.  by 
3  in.  are  much  used  in  New  Zealand.  The 
shorter  the  block  the  greater  is  the  saving  in 
cost,  as  the  use  of  the  9  in.  size  necessitates 
much  waste  of  timber  in  cutting.  The  shorter 
sizes  have  less  tendency  to  warp  and  become 
loose  through  "  rocking "  after  laying,  and 
they  are,  as  a  matter  of  fact,  more  easily 
seasoned,  and  there  is  no  reason  why  these 
reduced  lengths  should  not  be  employed  in  this 
country.  The  chief  timber  employed  for  soft 
wood  pavement  is  yellow  deal  and  Baltic 
redwood,  although  oak,  larch,  and  fir  have 
been  used  from  time  to  time. 

GENERAL  METHOD  EMPLOYED  IN  LAYING 
WOOD-BLOCK  PAVEMENTS. —  In  laying  wood 
pavements  of  all  descriptions  the  system 
known  as  close  blocking  is  to  be  recom- 
mended, excepting  where  the  gradient  is  steep. 
For  gradients  up  to  1  in  45  close  blocking  is 
considered  to  be  the  best  system,  but  with 
attention  to  the  method  of  laying  there  is  no 
reason  for  prohibiting  the  use  of  wood  blocks 
on  gradients  up  to  1  in  25,  or  even  1  in  15 
with  due  attention  to  gravelling  in  wet 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


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weather.  On  gradients  it  is  advisable  to 
space  the  transverse  joints  of  every  other  row 
of  blocks  about  an  inch  apart — or  in  special 
cases  it  may  be  advantageous  to  space  every 
row — so  as  to  give  a  better  foothold  for  horse 


FlG.  9. — Concrete  Paving. 

traffic  ;  and  the  camber  of  the  paving  on  hills 
should  be  less  than  that  usually  employed  on 
level  roads,  otherwise  horses  have  a  tendency 
to  slip  sideways,  with  extremely  dangerous 
results.  The  general  practice  is  to  make  the 
contour,  or  cross-section  of  the  road,  a  seg- 
ment of  a  circle,  giving  a  fulness  at  the 
"  shoulders  "  of  the  pave- 
ment, which  carry  the  traffic 
on  each  side  of  the  road. 
The  degree  of  convexity 
must  be  considered  in  con- 
junction with  the  longitu- 
dinal section,  as  to  whether 
this  be  flat  or  inclined.  On 
the  level  the  camber  allowed 
to  pavements  should  average 
1  in  60,  and  on  gradients 
this  should  be  from  1  in  70 
for  moderate  inclines,  and 
I  in  80  to  1  in  90  for  hills 
up  to  1  in  80  and  steeper. 
The  best  results  from  wood 
pavements  are  obtained  by 
laying  the  wood  blocks  with  the  fibre  vertical. 
Since  the  introduction  of  wood  for  the  paving 
of  streets  the  blocks  have  been  cut  in  various 
directions  to  the  grain  ;  for  instance,  in  De 
Lisle' s  system  the  blocks  were  cut  diagonally 
to  the  grain,  and  also  in  the  Trenaunay's 


system  used  in  France  and  introduced  into 
England  under  the  name  of  the  "  Lingo 
Mineral  Pavement."  By  placing  the  grain 
vertical,  the  life  of  the  wood  is  much  increased 
over  oblique  or  horizontal  cutting.  The  first 
question  of  importance  in  laying 
wood  pavements  is  to  provide  a 
thoroughly  reliable  foundation 
which  will  remain  intact  after  the 
wood  covering  is  worn  out.  Concrete 
is  the  best  material  for  this  founda- 
tion, and  this  should  be  constructed 
from  6  to  9  in.  deep,  over  a  well- 
consolidated  and  properly  formed 
road-bed.  The  face  of  the  concrete 
should  be  finished  to  a  smooth 
surface  and  formed  to  the  convexity 
required  for  the  wood  paving. 
Screeds  are  made  by  the  carpenter  to  fit  over 
the  road-bed.  These  are  placed  vertically 
across  the  road  at  distances  of  about  5  ft.  apart. 
The  spaces  between  these  vertical  screeds  are 
then  filled  with  concrete  of  good  quality,  the 
top  portion  being  finer  concrete  than  the  bulk. 
The  surface  is  rendered  smooth  and  to  an 


FIG.  10. — Concrete  Paving. 

equal  curvature  throughout  by  drawing  a 
suitable  straight-edge  across  the  screeds,  as 
shown  in  Fig.  10.  The  bed  for  the  blocks  may 
consist  of  sand  or  any  other  mobile  material 
on  the  concrete  foundation,  or  a  layer  of 
asphalte,  tar,  or  tarred  roofing  felt.  The 


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wood  blocks  should  be  dipped  three-quarters 
of  their  depth  into  a  boiling  composition  of 
coal-tar  and  pitch,  which  is  delivered  hot 
from  the  cauldron  on  to  the  work  in  shallow 
dipping-trays.  The  blocks  are  then  set  in 
their  places,  one  against  the  other,  in  perfectly 
straight  lines  from  kerb  to  kerb ;  and  as  soon 
as  a  few  blocks  are  set  in  their  places  by  hand 
a  flat  piece  of  wood  is  placed  against  their 
face,  and  with  the  assistance  of  a  sledge 
hammer  or  wrooden  mallet  the  blocks  are 
driven  perfectly  close  together,  both  trans- 
versely and  lengthwise.  On  completion  of  the 
day's  work,  and  before  any  of  the  surface  is 


exposed  to  rain,  the  joints  should  be  well 
grouted,  and  the  surface  also  coated  with 
boiling  tar  and  pitch,  and  immediately  covered 
with  a  f  in.  layer  of  fine  gravel  and  sand.  In 
laying  the  wood  blocks,  every  alternate  course 
must  be  commenced  with  a  half  block  in  order 
to  break  the  transverse  joints.  By  laying  the 
wood  blocks  diagonally  across  from  kerb  to 
kerb  there  should  be  less  wear  and  tear  on 
the  joints,  and  the  arris  of  the  blocks  should 
remain  intact  for  a  longer  period.  This  plan 
provides  a  much  more  comfortable  pavement 
to  traffic,  and  with  the  present-day  fast  modes 
of  locomotion  its  adoption  is  recommended  for 
the  consideration  of  engineers.  When  laying 
blocks  diagonally  across  streets  the  first  and 
last  blocks  in  each  row  will  be  cut  to  the 


angle  at  which  the  rows  are  laid  from  the 
channel  courses.  At  all  junctions  of  roads 
the  blocks  should  be  laid  diagonally,  as  shown 
in  Fig.  11,  otherwise  it  will  be  found  that  the 
wrheels  will  cut  the  transverse  unbroken  joints 
and  soon  cause  the  road  in  these  positions  to 
suffer  from  undue  wear.  The  channels  are 
usually  formed  by  laying  three  or  four  courses 
of  blocks  lengthways  with  the  street,  near  the 
kerbs.  Two  of  the  longitudinal  joints  in  these 
channel  courses  are  usually  made  about  an 
inch  wide,  with  the  one  near  the  kerb  filled 
with  mortar  of  medium  quality,  and  the  out- 
side joint  filled  with  clay  mixed  with  a  small 
quantity  of  lime.  These  will 
allow  for  the  expansion  of  the 
pavement,  and  when  the  outside 
joint,  which  is  filled  with  the  more 
tentative  material,  is  entirely 
closed  up  the  second  comes  into 
action.  It  is  a  mistake  to  make 
it  too  easy  for  the  pavement  to 
expand,  for  by  leaving  one  wide 
joint  of  about  1^  to  2  in.  clear- 
ance on  each  side  of  the  street 
merely  filled  with  compressible 
clay  the  weight  of  the  traffic  will 
cause  the  pavement  to  creep  im- 
perceptibly from  the  crown  of 
the  road  to  the  sides,  and  that 
which  is  sometimes  thought  to 
be  expansion  of  the  wood  is  nothing  more 
than  the  opening  of  the  longitudinal  joints; 
but  by  giving  the  pavement  a  sufficient 
support  to  butt  against  on  each  side  of  the 
road,  the  expansion  trouble  will  be  minimised 
the  pavement  joints  will  be  kept  water-tight, 
and  the  wear  of  the  blocks  will  be  increased. 
Should  the  pavement  show  signs  of  expanding 
and  a  slight  rise  in  the  centre,  it  is  an  easy 
matter  to  uncaulk  this  joint  and  re-make  it, 
when  the  road  has  taken  its  proper  bearing. 
This,  however,  rarely  occurs  if  the  nearest 
expansion-joint  is  properly  made.  It  is  most 
important  that  every  part  of  the  work  during 
the  process  of  laying  wood  pavements  should 
be  perfectly  dry.  The  foundation  must  be  as 
dry  as  possible,  the  wood  blocks  perfectly  dry, 


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MUNICIPAL   AND    SANITAEY   ENGINEERING. 


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and  the  tar  composition  must  be  distilled. 
The  work  is  expected  to  remain  on  completion 
for  a  lengthy  period,  and  whether  this  be  5 
years  or  '20  years,  it  is  a  question  depending 
very  much  upon  the  care  taken  on  all  points 
in  its  construction. 

Although  a  well-creosoted  soft  wood  pave- 
ment properly  laid,  and  with  strict  attention 
to  seasoning  and  quality  of  wood  before  treat- 
ment, will  make  a  comparatively  durable  and 
sanitary  pavement,  many  engineers  stats  that 
the  Australian  hard  woods  surpass  all  others 
from  every  reasonable  point  of-  view,  and 
although  the  first  cost  of  the  latter  exceeds 
that  of  the  soft  woods,  it  will  be  found  much 
the  cheaper  pavement  in  the  long  run.  They 
find  that  hard  wood  loses  less  by  shrinkage,  and 
costs  less  in  sanitation,  scavenging,  and  wear 
(but  this  is  a  very  debciteable  point)  ;  whilst 
soft  woods  cost  less  in  construction,  are  less 
noisy  under  the  traffic,  and  less  slippery  than 
hard  woods.  Hard  wood  will  cost  twice  that 
of  creosoted  deal,  and  in  some  cases  has  been 
found  to  wear  three  times  as  long.  It  will  be 
found  in  practice  that  if  by  once  laying  the 
hard  wood  pavement  will  have  a  life  of  75% 
over  and  above  that  of  soft  wood,  the  addi- 
tional cost  of  the  former  will  be  warranted.  If, 
however,  soft  wood  pavements  are  thoroughly 
gravelled  before  the  traffic  is  turned  on  to 
them,  and  watched  very  closely  and  gravelled 
at  periods  of  not  less  than  one  month,  the  life 
of  these  pavements  will  be  found  to  be  almost 
equal  to  that  of  hard  wood  pavements.  There 
is  one  great  advantage  with  soft  wood  pave- 
ments, viz.,  that  when  properly  and  skilfully 
maintained  the  surface  is  always  even,  while 
hard  wood  pavements  have  a  great  tendency 
to  become  bumpy.  Comparing  the  advan- 
tages and  disadvantages,  it  appears  that  soft 
woods  are  the  better  pavements  for  traffic  of 
any  description.  A  soft  wood  pavement  with 
foundation  complete  will  cost  from  10s.  to 
14s.  Qd.  per  square  yard,  and  the  usual  price 
for  hard  wood  paving  including  foundation  is 
15s.  to  17s.  Qd.  per  square  yard;  the  cost  of 
the  concrete  foundation  and  the  laying  being 
practically  the  same  in  each  case,  the  difference 


being  in  the  cost  of  the  blocks.  The  hard 
woods  of  the  Western  Australian  forest  are 
very  numerous,  but  the  two  principal  timbers 
employed  for  street  pavements  are  known  as 
Jarrah  and  Karri ;  the  former  growing  in 
greater  quantities  and  being  first  from  a  com- 
mercial point  of  view.  These  woods  get  ex- 
tremely hard  with  age,  and  are  then  almost 
indestructible.  In  appearance  there  is  but  little 
to  distinguish  the  Jarrah  from  the  Karri;  they 
are  both  red  in  colour,  hard,  heavy,  and 
tough,  but  the  Karri  does  not  dress  so  easily 
and  smoothly  as  the  Jarrah,  and  when  burnt 
the  former  leaves  a  good  deal  of  white  ash, 
but  the  latter  whilst  burning  looks  black  and 
leaves  practically  no  ash.  Karri  makes  a  less 
slippery  road  than  Jarrah.  It  is  difficult  to 
judge  the  better  of  the  two  woods  for  paving 
purposes,  so  long  as  they  are  both  well 
seasoned  before  laying.  Hard  wood  blocks 
require  to  be  well  seasoned,  and  Karri  more 
so  than  Jarrah.  The  following  results  were 
obtained  at  Penzance  by  seasoning  Jarrah  and 
Karri  blocks  and  experimenting  with  them  to 
ascertain  their  qualities  of  absorption,  shrink- 
age, and  expansion,  under  varying  conditions. 
The  greatest  penetration  in  Jarrah  was  one- 
sixteenth  of  an  inch,  and  the  least  depth  one 
thirty-second  part  of  an  inch,  whilst  Karri 
unseasoned  absorbed  four  drachms  of  water 
more  than  Jarrah  ;  but  when  both  were 
seasoned  Karri  gave  a  conflicting  result  of  two 
drachms  less  absorption  per  block  than  Jarrah ; 
and  in  seasoning,  the  former,  which  was 
originally  9  in.  long  and  3  in.  wide,  had  been 
reduced  to  8f  in.  long  and  2f  in.  wide.  If, 
therefore,  a  permanent  close  joint  is  required 
it  is  most  essential  that  all  the  wood  blocks 
should  be  stored  before  laying,  and  the  longer 
they  are  kept  the  better  the  pavement  will 
wear.  Well-seasoned  hard  wood  does  not 
expand  or  contract  to  any  appreciable  extent ; 
but  when  laid  soon  after  arrival  the  result 
varies.  In  hot  dry  weather  hard  woods 
shrink,  the  joints  open  and  become  filled 
with  grit  and  dust,  and  as  soon  as  the  wet 
weather  attacks  them  and  they  require  room 
for  expansion,  they  cannot  occupy  their 


377 


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original  positions  because  the  spaces  between 
them  are  filled  with  grit,  &c.  ;  so  the  whole 
covering  moves  towards  the  sides,  under  the 
weight  of  the  traffic,  and  the  expansion  takes 
place  at  the  expansion- joints  provided  near 
the  channel  on  either  side  of  the  street,  and 
without  the  expansion-joints  the  centre  of  the 
road  would  become  "  hog-backed."  Australian 
hard  wood  is  effective  in  resisting  moisture 
and  decay,  and  its  non-porous  character 
renders  it  a  particularly  sanitary  material  for 
pavements.  A  road  constructed  with  it  will 
dry  in  less  time  after  rain  than  pavements 
made  of  soft  wood  or  macadam. 

ASPHALTE  PAVEMENTS. — Asphalte  has  been 
used  for  the  surface  coating  of  carriageways 
with  considerable  success  for  the  past  40 
years  in  England,  and  has  also  been  largely 
employed  in  France  and  the  United  States  of 
America.  Natural  asphalte  is  a  form  of  lime- 
stone or  sandstone  in  union  with  mineral  pitch 
or  bitumen.  Limestone  asphaltic  rock  con- 
tains from  5  to  15  %  of  bitumen,  and  sandstone 
asphalte  contains  bitumen  in  varying  quan- 
tities of  50  %  and  upwards.  These  materials 
are  obtained  from  Val-de-Travers,  Switzer- 
land, Limmer  near  Hanover,  Brunswick, 
Ragusa,  Sicily,  France,  Germany,  and  Trini- 
dad. The  last-named  locality  produces  the 
best  bitumen  for  asphalte  pavements,  and 
many  of  the  extensively  used  thoroughfares  in 
London  have  been  laid  therewith.  This 
material  is  very  satisfactory  under  heavy  traffic. 
The  Val-de-Travers  rock  is  brought  from  the 
mines  into  this  country  in  its  raw  state,  where 
it  is  prepared  for  use.  It  is  ground  to  a 
fine  powder,  and  after  being  heated  is  con- 
veyed in  a  semi-plastic  condition  on  to  the 
works  in  covered  carts.  The  material  is  then 
evenly  spread,  by  means  of  rakes,  over  the 
surface  of  the  road  foundation,  and  compressed 
with  heated  rammers  or  pillows,  and  after- 
wards smoothed  off  with  irons  or  rollers.  This 
asphalte  is  usually  finished  to  a  thickness  of 
2  in.,  and  is  laid  on  a  foundation  of  6  in.  to 
8  in.  of  cement  concrete.  The  asphalte  cement, 
as  used  extensively  for  road  pavements,  is 
obtained  by  refining  crude  bitumen  from  the 


pitch  lake  of  Trinidad,  and  for  use  on  foot 
pavements  suitable  proportions  of  carbonate 
of  lime  and  sand  are  added.  In  order  that 
this  material  should  not  lack  plasticity  a  small 
quantity  of  residuum  oil  of  petroleum  is  added 
to  the  distilled  bitumen. 

MASTIC  ASPHALTE.  —  Mastic  asphalte  has 
practically  ceased  to  be  employed  for  pave- 
ments of  recent  years,  preference  being  given 
to  the  dry  process.  When  this  was  used  the 
mixture  of  ground  asphaltic  rock  and  bitumen 
was  heated  in  cauldrons  on  the  site  of  the 
work,  and  when  sufficiently  melted  dry  clean 
sand  and  gravel  were  added,  and  boiled  in  the 
liquor  for  an  hour  or  two.  The  material  was 
then  run  out  over  the  surface  of  the  founda- 
tion, and  smoothed  down  with  hot  irons  and 
rollers. 

BARNETT'S  ASPHALTE  resembles  the  mastic 
asphalte,  but  contains  a  small  proportion  of 
iron  ore,  which  was  supposed  to  increase  the 
life  of  the  pavement. 

CAMBER. — Asphalte  pavements  require  very 
little  camber  in  cross-section.  With  so  smooth 
a  surface,  the  water  will  have  no  difficulty 
in  draining  off  if  the  convexity  of  the  road  is 
made  with  an  average  rise  of  1  in  85,  or  less 
in  the  case  of  limestone  asphalte  pavements, 
these  being  more  slippery  than  Trinidad. 
Trinidad  asphalte  pavements  can  be  laid  on 
gradients  up  to  1  in  30  with  proper  attention 
to  cleaning,  and  limestone  rock  asphalte 
should  not  be  laid  on  gradients  over  1  in  50. 

ROADAMANT. — A  new  material,  manufactured 
by  the  "  Roadamant  Asphalte  Company,  Ltd.," 
has  been  introduced,  and  from  the  trials  made 
with  this  asphalte  composition  on  the  Victoria 
Embankment,  London,  and  other  places,  it 
would  appear  that  many  of  the  complications 
connected  with  the  laying  of  asphalte  pave- 
ments, which  prohibit  their  more  general 
adoption  in  some  provincial  towns,  will  be 
overcome.  The  asphaltic  material  is  incor- 
porated with  the  stones  of  the  respective 
districts  and  can  be  easily  laid  by  local 
road-makers.  "  Roadamant "  is  found  to 
give  a  very  high  record  of  resistance  to 
crushing,  compares  very  favourably  with 


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MUNICIPAL   AND   SANITAKY   ENGINEEEING. 


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other  forms  of  asphalte,  and  its  use  is  cal- 
culated to  considerably  reduce  the  ultimate 
cost  of  road  repairs.  The  manufacturers 
claim  that  it  is  impervious,  dustless,  silent, 
expeditiously  laid,  comparatively  inexpensive, 
and  possesses  the  feature  of  being  non-slippery 
to  horses  and  other  traffic.  When  laid  on  a 
foundation  of  6  in.  of  concrete  it  costs  from 
10s.  to  11s.  per  yard  superficial,  including 
foundation,  and  its  life  is  claimed  to  be  from 
10  to  15  years,  according  to  the  amount  of 
traffic  to  which  it  is  subjected.  The  manu- 
facturers also  claim  that  the  average  cost 
per  superficial  yard  per  annum  is  less  than 
any  other  description  of  pavement,  being 
only  10'132^.  per  square  yard  per  annum, 
including  first  cost,  spread  over  a  period  of 
15  years. 

SANITARY  BLOCK  PAVEMENT.  — This  asphaltic 
pavement  has  been  extensively  used  in  the 
United  States  of  America,  and  is  now  laid  by  the 
Hastings  Pavement  Company  in  this  country. 
It  consists  of  asphaltic  blocks  made  of  a  mixture 
of  refined  lake  pitch  and  crushed  trap-rock, 
incorporated  at  a  temperature  of  200°  F. 
Whilst  at  this  temperature  the  material  is 
manufactured  into  blocks  under  a  pressure  of 
120  tons.  The  blocks  measure  4  in.  by  12  in. 
by  3  in.,  and  4  in.  by  12  in.  by  4  in.,  and 
they  weigh  13^  Ibs.  and  18  Ibs.  respectively. 
Asphaltic  pavements  should  be  laid  on  a  con- 
crete foundation  similarly  constructed  to  tbat 
used  for  wood-paved  carriageways,  but  with 
less  camber.  The  surface  of  the  concrete  must 
be  quite  dry  at  the  time  of  laying  the  asphalte, 
otherwise  the  pavement  when  completed  will 
be  found  full  of  little  holes  just  beneath  the 
surface,  and  these  will  cause  the  road  to  wear 
badly. 

TAR  MACADAM. — There  is  perhaps  no  pave- 
ment of  more  varying  qualities  than  tar 
macadam.  Simple  as  its  construction  may 
appear  to  the  inexperienced,  its  success  depends 
upon  strict  attention  to  the  proper  treatment 
of  the  materials  used.  The  preparation  and 
incorporation  of  the  cementing  composition, 
the  conditions  upon  which  the  work  is  executed, 
and  the  description  of  traffic  to  which  it  is  to 


be  subjected  must  all  enter  into  the  computa- 
tion, as  neglect  of  any  one  point  will  militate 
against  success.  If  tar  macadam  is  efficiently 
made,  it  forms  one  of  the  most  valuable  of 
materials  at  the  disposal  of  the  road  engineer, 
and  when  properly  laid  will  be  found  to  be 
durable,  and  is  capable  of  withstanding  a 
considerable  amount  of  traffic.  The  usual 
method  adopted  in  preparing  tar  macadam  for 
roads  is  to  heat  clean  macadam  stones  over 
purposely  made  furnaces,  and  then  to  mix  them 
with  a  proportion  of  boiling  tar,  pitch,  and 
creosote  oil,  the  relative  proportions  being  one 
barrel  of  coal  tar,  1  cwt.  of  pitch,  and  4  gallons 
of  creosote  oil.  The  mixture  of  stones  and  tar 
is  ready  for  use  soon  after  cooling,  and  is 
put  on  the  dry  road  formation  in  two  layers. 
The  bottom  layer  is  about  4  in.  in  thickness 
and  composed  of  large-sized  stones  about 
2J  in.  in  diameter,  and  the  top  layer  or  sur- 
face coating  is  about  2  in.  in  thickness, 
composed  of  stones  about  1  in.  in  diameter. 
Each  coat  is  well  rolled,  and  the  total  thick- 
ness varies  from  3  in.  to  6  in.  The  surface 
is  well  sanded  previous  to  the  traffic  being 
admitted  over  it.  Tar  macadam  can  be  used 
for  repairs  to  roads,  channelling,  footpaths, 
and  a  variety  of  other  purposes. 

THE  VAL-DE-TRAVERS  ASPHALTE  MACADAM 
has  met  with  success  where  it  has  been  laid, 
and  its  price  places  it  within  the  reach  of 
most  highway  authorities.  In  this  process 
the  ordinary  asphalte  rock  is  broken  up  into 
angular  pieces,  each  capable  of  passing  in 
any  direction  through  a  2  in.  ring  ;  it  is  then 
carefully  spread  and  levelled  over  the  surface 
of  the  road  to  an  even  thickness  of  about 
4^  in.  and  compressed  by  rolling.  A  steam 
roller  of  10  tons  weight  will  compress  the 
thickness  to  about  3^  in.  If  the  material  is 
to  be  used  on  a  road  already  formed  and 
having  a  good  foundation,  nothing  more  is 
required  than  the  removal  of  the  top  crust  to 
a  sufficient  depth  to  take  the  new  covering, 
the  road-bed  being  well  rolled  and  ready  to 
receive  the  asphalte.  In  the  case  of  a  new 
road,  or  one  not  having  a  sufficiently  good 
foundation,  the  ground  must  be  taken  out  and 


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ENCYCLOPAEDIA   OF 


ROA 


removed  to  the  necessary  depth,  find  a  layer 
of  broken  stone,  clinkers,  or  brick  rubbish, 
about  6  in.  thick  and  well  consolidated  by 
rolling  and  formed  to  the  proper  camber,  will 
be  all  that  is  required  to  form  the  foundation, 
and  upon  this  is  laid  the  surface  coat  of 
asphalte.  Val-de-Travers  asphalte  macadam 
forms  a  perfectly  smooth,  even,  noiseless,  and 
sanitary  pavement,  affords  a  good  foothold 
for  horses,  and  wears  well  under  all  classes  of 
traffic. 

"  PLASCOM  "  PATENT  COMPOSITION  GROUT.— 
This  material,  which  is  manufactured  by  the 
Plasco-Bitumite  Company,  Ltd.,  has  proved 
itself  to  be  an  inexpensive  preparation  for  add- 
ing to  the  lifeof  macadamised  roads,  and  renders 
them  more  sanitary.  The  mode  of  construc- 
tion of  carriageways  and  other  works  recom- 
mended by  this  company  is  as  follows : — In 
the  case  of  remacadamising  an  existing  road 
the  ordinary  method  should  be  adhered  to, 
viz.  : — First  scarify  the  surface,  regulate  and 
steam  roll  the  foundation  exposed  until  it  is 
thoroughly  consolidated.  Upon  this  lay  the 
necessary  coating  of  granite,  furnace  slag,  lime- 
stone, or  other  material  proposed  to  be  used, 
and  if  not  more  than  4  in.  in  thickness  it  may  be 
treated  in  one  layer.  Bring  all  the  work  to  as 
near  the  finished  levels  as  possible,  with  proper 
falls  and  camber,  and  after  again  steam  roll- 
ing prepare  the  surface  for  grouting.  Care 
should  be  taken  to  see  that  "  Plascom  "  is  well 
boiled  to  a  good  temperature  (say  300°  F.) 
before  using,  as  it  will  then  become  quite  fluid 
and  run  freely.  Next  proceed  to  pour  the 
compo  over  the  surface  material  above  referred 
to  and  fill  up  the  whole  of  the  interstices  until 
thoroughly  grouted,  cover  the  surface  with  a 
thin  layer  of  \  in.  chippings  while  the 
"Plascom"  is  hot,  and  roll  with  the  front 
wheels  of  roller  almost  immediately  to  keep 
work  in  shape,  and,  after  cooling  down  (but 
before  the  compo  sets,  wrhich  it  does  very 
quickly),  well  and  thoroughly  roll  to  finished 
surface.  The  manufacturers  of  this  material 
claim  that  the  ordinary  traffic  may  be  turned 
upon  each  section  immediately  it  is  completed 
and  no  damage  is  caused  to  the  new  surface. 


The  composition  can  be  easily  liquefied  in  an 
ordinary  tar  boiler.  If  the  boiler  is  first  only 
filled  to  one-fourth  of  its  capacity,  and  after 
the  composition  becomes  liquefied  fed  until  the 
necessary  quantity  is  put  in,  the  grouting 
material  will  be  ready  for  use  more  quickly. 
In  order  to  thoroughly  incorporate  the  mate- 
rial and  derive  the  full  benefit  from  the 
more  valuable  properties  of  "  Plascom,"  the 
material  should  be  thoroughly  stirred,  and 
especially  is  this  the  case  when  drawing  off 
the  liquid  through  the  tap.  The  same  pro- 
cedure may  be  followed  so  far  as  it  applies  in 
the  treatment  of  new  roads,  but  it  is  very 
essential  that  the  foundation  should  be  con- 
structed with  good  hard  material,  not  less  than 
6  in.  thick,  and  the  interstices  filled  up  with 
small-sized  stone,  and  .well  rolled  before  the 
surface  layer  of  broken  stone  is  put  on.  For 
grouting  sett  paving  the  packing  should  be 
cubical  in  shape,  with  a  minimum  size  of 
f  in.,  dry  and  free  from  dust,  and  a  thorough 
grouting  from  top  to  bottom  is  then  assured. 
Clean  gravel  of  the  size  mentioned  gives 
excellent  results.  One  ton  of  "Plascom  "  will 
grout  50  yards  super,  of  paving.  "Plascom," 
if  well  boiled  when  used  for  grouting  wood 
paving,  will  run  as  freely  as  pitch  and  creosote 
oil,  and  is  much  more  satisfactory  owing  to 
its  plastic  and  adhesive  properties.  It  sets 
more  quickly  than  pitch.  This  is  particularly 
advantageous,  especially  in  case  of  repairs  to 
streets  where  the  vehicular  traffic  may  be 
congested,  as  it  acts  as  a  safeguard  against 
foreign  matter  being  driven  into  the  body  of 
the  grout,  prevents  water  percolating  through 
the  bad  joints  into  the  under  bed,  and  pre- 
serves the  paving.  One  ton  of  "  Plascom  " 
will  grout  70  yards  super. 

"  TARMAC." — This  material  is  manufactured 
from  ironstone  slag  and  is  thoroughly  im- 
pregnated with  tar  oils.  It  is  supplied  from 
the  works  ready  for  immediate  use.  The  mate- 
rial is  easily  laid  and  consolidated  with  the 
minimum  duration  of  rolling,  and  when 
finished  the  road  is  impervious  and  durable, 
and  possesses  the  advantages  of  a  maca- 
damised road  without  its  drawbacks.  It  forms 


380 


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MUNICIPAL   AND    SANITAKY   ENGINEERING. 


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an  economical  road  covering,  and  cleansing 
charges  are  reduced  by  its  use.  The  following 
details  for  the  application  of  "Tarmac"  are 
recommended  by  the  company  : — For  roadway 
purposes,  before  applying  "  Tarmac,"  the  road 
surface  should  be  smooth,  and  all  loose  stones 
removed.  It  is  not  necessary  to  have  a  special 
concrete  foundation  for  "  Tarmac."  Holes 
and  inequalities  in  the  surface  should  be  cut 
out,  first  tarred,  and  then  patched  with  fine 
"  Tarmac,"  these  patches  to  be  well  rammed 
with  a  road  rammer  until  the  surface  is  level. 
"Tarmac"  being  quite  impervious  to  water, 
a  camber  of  1  in  50  is  sufficient  to  keep  the 
road  dry.  The  first  coating  should  be  carefully 
spread,  rolled  to  a  depth  of  about  1^  in.  with  a 
roller  of  medium  weight,  and  any  shaping  of  the 
road  required  must  be  done  in  this  applica- 
tion. This  layer  should  have,  if  possible,  two 
days'  drying  before  applying  the  second  layer. 
The  finished  face  is  best  made  with  a  close 
layer  of  finer  material,  1J  in.  gauge  evenly 
spread,  and  rolled  to  a  thickness  of  1^  in., 
the  total  final  thickness  being  about  4  in. 
"When  the  whole  is  sufficiently  rolled,  a  fine 
covering  of  slag  dust  should  be  carefully 
spread  over  the  surface,  and  later  the  surplus 
should  be  swept  off.  It  is  not  advisable  to  use 
too  heavy  a  roller,  one  of  about  six  or  seven 
tons  is  sufficient.  Ironstone  slag  not  treated 
(of  size  to  pass  through  a  3£  in.  ring)  is 
very  suitable  for  the  foundations  of  new  roads. 
In  unloading  trucks  the  doors  should  be  opened 
and  the  material  shovelled  from  the  bottom  in 
order  to  insure  its  being  properly  mixed. 

BRICK  PAVEMENTS. — Bricks  have  been  used 
for  paving  purposes  in  the  United  States  of 
America  and  other  countries  for  several  years, 
but  they  have  not  been  extensively  adopted 
for  pavements  in  England.  Trials  have  been 
made  from  time  to  time  in  various  localities 
in  this  country  with  varying  results,  more 
failures  having  to  be  recorded  than  successes. 
Bricks  are  very  apt  to  wear  unevenly,  to  chip 
and  become  slippery.  In  the  United  States  of 
America  brick  pavements  are  recommended  as 
one  of  the  best  forms  of  paving  materials. 
In  selecting  bricks  for  pavements  care  should 


be  exercised  to  see  that  only  those  of  the  best 
quality  are  used.  They  should  measure  8J  in. 
by  2^  in.  by  4  in.,  absorb  not  more  than 
2^%  of  water,  when  immersed  for  12  hours 
after  being  thoroughly  dried,  stand  a  cross- 
breaking  stress  of  2,500  Ibs.  if  made  from 
a  good  shale,  should  be  free  from  lime, 
highly  burnt  and  annealed,  and  of  uniform 
colour,  especially  when  used  for  footpaths. 
They  should  be  hard,  tough,  and  impervious, 
and  have  a  resistance  to  crushing  of  at  least 
7,500  Ibs.  to  the  square  inch.  The  edges  of 
street  paving  bricks  should  be  pressed  and 
slightly  rounded.  Brick  pavements  should  be 
laid  on  a  foundation  of  concrete  similar  to 
that  recommended  for  wood  and  asphalte 
pavements.  The  bricks  are  bedded  close 
together  on  a  thin  layer  of  mortar,  over  the 
foundation,  each  row  breaking  joint  as  in  the 
case  of  wood  paving,  and  at  the  completion  of 
every  few  yards  of  work  the  surface  should  be 
carefully  rammed  till  the  bricks  are  level.  As 
soon  as  the  surface  is  levelled  and  formed  to 
the  proper  camber,  the  joints  should  be 
grouted  with  liquid  cement. 

PAVING  SETTS,  CUBES,  OR  BLOCKS  OF  STONE, 
when  used  for  paving  purposes,  are  durable 
and  cleanly.  Granite  becomes  slippery,  is 
immensely  hard  and  unyielding  under  the 
feet  of  horses,  is  noisy  and  unpleasant  for 
all  descriptions  of  light  traffic.  The  setts  for 
paving  purposes  should  be  4  in.  across  and 
have  a  depth  varying  from  5  in.  to  8  in.  The 
length  should  be  equal,  not  exceeding  12  in., 
and  should  be  laid  so  as  to  break  joint  with 
their  lengths  across  the  road.  The  foundation 
should  be  formed  of  6  in.  of  concrete  and  the 
setts  should  be  bedded  in  1  in.  thickness  of 
asphaltic  concrete  or  chippings  and  cement, 
and  on  completion  thoroughly  rammed  to  a 
level  surface  and  grouted  with  hot  liquid 
asphalte  until  the  joints  are  quite  full.  Sand- 
stones of  good  quality  make  a  less  slippery 
pavement,  but  are  not  so  durable  as  granite. 
A  comparatively  new  method  of  sett  paving  has 
been  introduced  into  England  called  the 
"  Durax  "  system,  in  which  the  best  descrip- 
tions of  stones  are  arranged  in  a  manner  so 


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as  to  afford  the  maximum  amount  of  comfort 
combined  with  durability  and  efficiency,  while 
its  cost  will  favourably  compare  with  most  of 
the  forms  of  pavement  having  far  less  wearing 
qualities.  The  "  Durax  "  system  of  armoured 
roads  consists  of  Durax  cubes,  which  are 
machine-made,  so  as  to  assure  the  closest 
joint  between  the  cubes  of  stone.  These  are 
laid  side  by  side  in  segmental  rows  on  a 
solid  foundation  and  bedded  on  sand.  The 
pavement  thus  presents  the  appearance  of 
Mosaic  work  laid  in  a  series  of  segmental 
curves.  The  traffic  in  passing  over  this  form 
of  road  is  distributed  over  a  larger  area  than 
would  be  the  case  in  an  ordinary  sett-paved 
roadway,  and  both  noise  and  wear  are  reduced, 
and  many  of  the  former  objections  to  the 
stone  pavement  are  eliminated.  It  is  very 
durable  and  comparatively  inexpensive  to 
adopt,  the  initial  cost  comparing  favourably 
with  that  of  soft  wood  paving  and  possessing 
a  much  longer  life.  This  system  of  paving 
has  been  much  used  in  Germany,  Austria,  and 
Italy,  and  highly  satisfactory  work  has  already 
been  carried  out  within  the  borders  of  this 
country.  R.  H.  B.  &  F.  L. 

Road  Watering. — Necessity  and  Objects- 
Methods  —  Types  of  Apparatus  —  Cost  —  Dust 
Palliatives. 

The  Public  Health  Act,  1875,  s.  42,  gives 
powers  to  the  local  authority  to  themselves 
undertake  or  contract  for  the  proper  watering 
of  streets  for  the  whole  or  any  part  of  their 
district. 

NECESSITY  AND  OBJECTS  OF  STREET  WATER- 
ING.— Street  watering  is  a  necessity  in  dry 
weather  to  lay  the  dust  caused  by  the  disinte- 
gration of  road  surfaces  by  traffic  and  other 
means.  Also  paved  roadways  are  apt  to  get 
very  slippery  in  hot  weather,  and  by  the  action 
of  the  heat  the  pitch  in  the  joints  becomes 
melted  and  runs  out.  Added  to  this  the  great 
heat  thrown  up  from  paved  roads  is  very 
distressing  to  vehicular  and  pedestrian  traffic. 
Systematic  watering  alleviates  these  defects 
to  a  certain  extent  and  makes  the  air  more 
cool  and  congenial.  Many  of  the  principal 


thoroughfares  in  large  cities  and  towns  are 
thoroughly  washed  during  the  night,  a  practice 
which  has  great  advantages  from  a  sanitary 
point  of  view. 

OBJECTIONS.  —  Objections  are  sometimes 
raised,  because  watering,  if  not  carefully 
carried  out,  creates  a  thin  mud,  which  becomes 
dangerous  to  cyclists  and  others.  Also  exces- 
sive watering  washes  away  the  binding 
material  and  deteriorates  the  road  surfaces. 

Pioad  watering  is  now  being  largely  replaced 
by  "  tarring  "  of  the  surfaces  with  advantages 
from  every  point  of  view. 

METHODS. — There  are  two  methods  of  water- 
ing roads,  viz  :— (1)  by  hand,  in  which  a  hose 
and  reel  or  portable  iron  tubes  are  used ;  and 
(2)  by  vehicles,  drawn  either  by  horses  or  by 
steam.  The  former  is  very  seldom  used,  most 
towns  emploving  either  horse-drawn  vehicles 
or  motor-vans.  In  Paris,  however,  and  some 
of  the  London  boroughs  and  certain  provincial 
towns,  the  "hose-reel"  is  adopted.  Hose- 
pipes are  also  attached  to  the  fire  hydrants  in 
the  streets  and  the  water  is  delivered  on  to 
the  road  through  a  rose  nozzle  or  other  appli- 
ance. This  sometimes  proves  to  be  objection- 
able in  wide  streets  owing  to  the  uneven 
distribution  and  the  inconvenience  to  the 
traffic,  but  it  is  a  great  advantage  in  washing 
out  paved  markets  and  the  adjacent  streets. 

TYPES  OF  APPARATUS. — Watering-carts  can 
be  fitted  with  "tell-tale  indicators,"  which 
register  the  number  of  loads  used  during  the 
day.  These  are  useful  in  checking  the  driver's 
work,  and  also  in  keeping  an  account  of  the 
quantity  of  water  used. 

Distributors  are  now  manufactured  so  that 
the  supply  of  water  on  to  the  surface  can  be 
regulated  to  a  nicety.  One  form  of  modern 
distributor  is  divided  into  four  compartments, 
each  of  which  is  fed  from  the  tank  by  a  sepa- 
rate valve  and  pipe.  This  distributor  is  so 
constructed  that  by  the  use  of  the  two  upper 
compartments  a  lighter  spray  will  be  delivered 
on  the  surface  than  if  the  lower  compartment 
were  used.  Any  of  these  compartments  may 
be  used  alone,  so  that  either  side  of  the  distribu- 
tor can  be  worked  when  passing  vehicles  or 


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MUNICIPAL    AND    SANITARY   ENGINEERING. 


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watering  narrow  strips.  Willacy's  &  Greves 
rotary  water- sprinklers  are  efficient  means  of 
distributing  water  in  wide  streets  as  well  as 
streets  of  average  width.  Water  distributed 
by  these  rotary  machines  is  more  evenly 
sprinkled  than  when  a  box  arrangement  is 
used,  and  there  is,  therefore,  a  saving  in  the 


front  of  vehicle.  D  is  the  flanged  pipe  for 
flushing  gullies,  &c.,  and  can  either  be  left 
plain  or  screwed  and  fitted  with  union  E  for 
hose. 

The  foot  lever  is  arranged  so  as  to  operate 
the  piston  B  in  four  distinct  movements, 
either  exposing  two,  four,  or  six  rows  of 


-FIG  I- 

Longitudinal 
Section  of  Dis- 
tributor Head. 


Longitudinal  Section  of  Distributor  Head  on  a  Line  at  Eight 
Angles  to  Fig.  1 . 


relative  cost.  There  are  many  makes  of 
sprinklers  on  the  market,  but  reference  will 
only  be  made  to  the  "Warwick  sprinkler" 
(see  Figs.  1,  2,  and  3). 

A  is  a  gun-metal  cylinder  perforated  with 
holes  for  about  two-thirds  its  circumference 
for  the  distribution  of  water.  B  is  a  piston 
regulating  the  supply  of  water  from  the  con- 
necting head  K.  C  is  the  piston  rod,  operated 
by  lever  H,  connected  to  the  foot  levers  on 


-  FIG  3  - 


End   View   of 
Distributor. 


holes  L,  in  addition  to  the 
flushing  pipe  D. 

The  width  of  spread  is  con- 
trolled by  a  slide  A1,  embracing 
the  cylinder  for  about  a  third 
of  its  circumference  to  cover 
up  the  holes  more  or  less  as 
desired. 

When  the  flushing  valve  is 
in  use  this  slide  is  dropped  to 
its  fullest  extent  so  as  to  prevent 
the  water  being  distributed  in 
any  but  a  downward  direction. 


By  releasing  the  studs  J,  the  distributing 
head  may  be  adjusted  to  distribute  the  water 
more  or  less  in  the  centre  of  the  road,  and, 
if  desired,  the  centre  of  the  road  or  tramway 
track  may  be  left  dry  for  a  space  of  about 
6  or  7  ft. 

The  distributor  is  supplied,  attached  to 
every  possible  form  and  size  of  vehicle,  with 
circular  or  rectangular  tank,  and  mounted  on 
either  two,  three,  or  four  wheels. 


383 


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ENCYCLOPEDIA   OF 


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The  van  is  fitted  with  a  branch  outlet  pipe 
on  the  underside  which  is  connected  to  the 
distributing  heads  by  means  of  india-rubber 
pipes. 

There  are  no  valves  or  fittings  of  any  kind 
inside  the  tank. 

There  are  two  valves  only,  each  of  which  gives 
ten  or  more  variations  in  the  width  and  grade 
of  spread  and  operates  the  flushing  connections, 
according  to  the  distance  the  valve  is  opened. 
This  is  all  worked  by  means  of  foot  or  hand 
levers,  working  from  the  driver's  seat,  without 


the  hydrants,  stand  posts,  or  valves,  and  it 
will  be  found  that,  on  suitable  gradients,  a 
four-wheeled  van  which  has  a  capacity  of  350 
to  450  gallons  will  perform  more  work  in  a 
given  time  than  a  two-wheeled  cart  which  has 
a  capacity  of  225  to  250  gallons.  It  has  been 
found  that  the  difference  in  the  work  done 
is  on  the  average  at  least  25  °/0  in  favour  of 
the  four-wheeled  van.  Motor-driven  watering- 
vans,  which  carry  a  much  larger  quantity  of 
water  than  horse-drawn  carts  or  vans,  are, 
as  already  mentioned,  used  in  some  towns 


FIG.  4. — The  Warwick  Sprinkler. 


the  driver  losing  control  of  the  horse  by  leaving 
his  seat. 

The  water  is  distributed  at  right  angles  to 
the  direction  in  which  the  van  travels,  thereby 
obtaining  a  much  more  effective  distribution 
of  the  water  than  with  an  ordinary  van,  Fig.  4. 

COST. — In  busy  and  wide  thoroughfares, 
where  traffic  is  heavy,  motor  water  ing- vans 
have  been  found  economical.  Experiments 
have  been  made  in  various  towns  to  ascer- 
tain the  quantity  of  water  required  for  road 
watering  during  the  dry  summer  season, 
and  it  has  been  found  that  with  valves  at 
convenient  distances  apart  a  water-cart  will 
water  from  25,000  to  35,000  square  yards  four 
times  a  day.  A  gallon  of  water  will  cover  an 
area  of  four  square  yards  of  road  surface. 
Much  time  is  lost  in  travelling  to  and  from 


with  satisfactory  results.  Figures  giving 
comparative  cost  of  these  three  systems,  i.e., 
horse-drawn  vans,  horse-drawn  carts,  and 
motor  water-vans,  are  difficult  to  obtain,  but 
the  following  information  from  the  "  Municipal 
Engineer's  Specification,"  Vol.  I.,  p.  9,  will 
prove  useful : — "  In  Bradford,  watering  by 
means  of  ordinary  water-carts  costs  6%d.  per 
load,  or  4s.  Wd.  per  mile  of  road.  Watering 
by  hand  with  hose  costs  4s.  5d.  per  mile  of 
road,  and  watering  by  means  of  a  revolving 
disc  van  costs  5%d.  per  load  of  350  gallons,  or 
2s.  Srf.  per  mile  of  road."  "  Santo  Crimp  gives 
the  average  cost  of  watering  at  3'86s.  per  mile 
of  road  8  yards  wide."  Road  watering  by 
means  of  horse  water-carts  and  vans  and 
motor  water-vans  in  the  metropolitan  borough 
of  Wands  worth  works  out  at  £39  8s.  6d.  per 


384 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


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mile  of  road  per  year.  Motor-vans  sprinkle  at 
the  rate  of  about  '192  gallon  to  *078  gallon  per 
square  yard.  H.  P.  Boulnois,  in  his  "  Muni- 
cipal and  Sanitary  Engineer's  Handbook," 
1898,  p.  309,  gives  the  cost  as  obtained  from 
Reading  at  9s.  5d.  per  day  covering  a  length 
of  2,981  yards  double  width  of  roadway.  If  the 
work  is  capable  of  being  done  in  one  width  the 
length  will  be  5,962  lineal  yards.  This  will 
give  a  cost  in  the  former  case  of  about  5s.  Qd. 
per  mile,  and  in  the  latter  case  of  about  2s.  9d. 
per  mile  of  roadway. 

DUST  PALLIATIVES  OR  MATERIALS  MIXED 
WITH  THE  WATER. — It  is  sometimes  advisable, 
in  order  to  successfully  cope  with  the  dust 
nuisance  where  special  preventative  measures 
have  not  been  adopted,  to  add  some  form 
of  binding  material  to  the  water  used  for 
sprinkling  the  surface  of  the  roads.  A  large 
number  of  such  preparations  have  been  intro- 
duced during  recent  years  with  more  or  less 
success.  Among  them  may  be  mentioned 
the  following:— 

Calcium  Chloride  Crystals.  —  These  are 
placed  in  the  water-van  or  cart  and  slowly  dis- 
solved in  the  water.  A  small  quantity  will 
be  found  sufficient  if  applied  regularly.  This 
chemical  will  dissolve  in  sea  water  as  well 
as  fresh  water,  and  in  districts  where  salt 
water  is  used  for  watering  the  roads  it  will 
be  found  doubly  advantageous.  It  is,  how- 
ever, too  slippery  to  be  used  upon  hills. 

Emulsifix. — This  is  a  dust- layer  or  palliative 
when  mixed  with  water.  It  contains  emulsified 
tar,  and  it  is  claimed  that  its  use  saves  two- 
thirds  the  cost  of  watering  with  fresh  water. 
The  material  is  only  applied  occasionally  from 
seven  to  ten  times  during  a  dry  summer,  and 
on  account  of  the  small  percentage  of  oil  used 
each  time,  no  ill  effects  appear,  and  sloppiness 
is  thus  avoided.  There  are  many  other  dust- 
laying  preparations  on  the  market,  but  these 
are  too  numerous  to  refer  to  in  detail  in  the 
present  article. 

Sea  Water,  the  uses  and  objections  to. — 
Sea  water  has  been  extensively  used  for  street 
watering  in  several  seaside  towns  with  satis- 
factory results.  It  has  been  found  that  by  its 

385 


use  as  compared  with  fresh  water  (a)  the 
surfaces  of  the  roads  remain  damp  for  a 
longer  period ;  (b)  it  hardens  the  surface  of 
the  road,  forming  a  crust  which  prevents  to 
a  large  degree  the  nuisance  from  dust ;  (c)  a 
much  smaller  quantity  is  necessary,  thereby 
reducing  the  cost,  not  only  of  watering,  but 
of  repairs  to  the  surface ;  (d)  it  preserves 
wood  pavements  and  makes  them  easier  to 
cleanse ;  (e)  it  has  also  been  contended  by 
some  that  it  retards  the  decomposition  of 
refuse  on  the  streets,  thus  preventing  dis- 
agreeable smells.  Among  the  objections  to 
its  use  are : — (a)  Damage  is  caused  to  the 
varnish  on  carriages  ;  (b)  the  dust  arising  con- 
tains salt  and  is  injurious  to  tradesmen's  goods  ; 
(c)  the  road  surface  is,  after  several  applica- 
tions, covered  with  a  coat  of  salt,  and  thorough 
washing  and  sweeping  is  necessary  to  the 
surface  to  remove  this  coating. 

F.  L.  &  R.  H.  B. 


Rust  Chambers. — Pockets  or  recesses 
provided  at  the  bottom,  or  in  bends  of  iron 
ventilation  shafts,  for  receiving  and  collecting 
rust  scales,  and  so  preventing  these  from 
blocking  the  pipes. 

Sand  Filtration.  (See  "FILTRATION  OF 
WATER.") 

Sanitary  Fittings. — This  term  embraces 
closets,  baths,  and  other  such  appliances  fixed 
within  buildings.  For  details  see  under 
separate  headings.  Unless  carefully  selected 
and  properly  placed  and  fixed,  sanitary  fittings 
are  liable  to  belie  their  name  and  to  prove 
the  more  dangerous  owing  to  their  position 
in  the  interior  of  the  house.  In  general,  they 
should  be  as  simple  in  construction  and  design 
as  possible;  the  former  in  order  that  there 
shall  be  as  little  as  may  be  to  get  out  of  order, 
the  latter  to  promote  cleanliness.  Nooks  and 
corners  and  all  ornamentations,  whether 
raised,  sunk,  or  coloured,  should  be  avoided, 
as  they  tend  to  harbour  and  hide  dust  and 

c  c 


SAN 


ENCYCLOPEDIA   OF 


SAN 


dirt.  All  surfaces  liable  to  be  fouled  should 
as  far  as  practicable,  be  self-cleansing,  and, 
if  this  is  not  possible,  so  arranged  and  con- 
structed as  to  show  the  soiled  surfaces  and 
permit  of  their  cleaning  by  hand.  Particular 
attention  must  be  paid  to  the  overflows  of 
fittings,  which  detail  is  the  one  most  likely 
to  prove  a  nuisance.  These  overflows  are 
only  occasionally  flushed,  rapidly  become 
coated  with  filth,  and  are  apt  to  give  off  musty 
and  insanitary  emanations.  Most  fittings  in 
the  past,  and  many  at  the  present  time,  are  so 
constructed  that  the  overflow  pipes  are  invisible 
and  incapable  of  being  got  at,  if  at  all,  without 
the  removal  of  bolts  and  screws  which  the 
average  householder  or  maid  is  incapable  of 
removing.  The  ^only  overflows  which  should 
be  tolerated  are  those  in  the  form  of  an  open 
weir,  which  will  allow  of  the  insertion  of  a 
brush  for  cleaning  purposes,  or  the  detachable 
trumpet  overflows  with  which  many  baths, 
sinks,  and  lavatory  basins  are  now  fitted. 

Soap  dishes  in  lavatory  basins,  baths,  and 
sinks,  but  more  especially  in  the  first-named, 
are  also  frequently  improperly  made.  They 
often  consist  of  sunk  dishes  drained  into  small 
inaccessible  pipes  through  one  or  more  small 
holes  in  their  bottoms.  The  pipes  leading 
from  these  dishes  are  inaccessible  and  rapidly 
give  rise  to  nuisance  due  to  decomposing 
deposits  of  soap.  The  holes  are  also  apt  to 
become  clogged  and  to  lead  to  the  retention 
of  water  in  the  soap  trays.  For  this  reason 
undrained  dishes  should  also  be  avoided. 
The  soap  trays  to  be  preferred  are  those 
which  drain  through  a  small  open  channel 
into  the  basin  or  other  fitting  upon  which 
they  are  provided. 

Each  fitting,  whatever  its  nature  or  object, 
must  be  trapped  as  near  as  possible  to  its  out- 
let by  means  of  an  efficient  trap  (see  "TRAPS"), 
and  as  a  general  rule  it  is  well  to  make  use  of 
only  such  fittings  in  which  the  trap  is  separate 
from  the  appliance  proper ;  as,  should  it  be 
necessary  to  remove  the  latter,  the  trap  need 
not  be  disturbed,  but  may  be  left  on  the 
waste  or  soil  pipe  to  continue  its  function  of 
excluding  foul  air  from  the  house. 


The  trap  must  be  of  the  same  or  of  a 
smaller  sectional  area  than  that  of  the  outlet 
under  which  it  is  fixed,  due  allowance  being 
made  for  the  space  obstructed  by  the  outlet 
grating,  where  such  exists.  Were  it  larger 
the  flow  from  the  fitting  would  not  be  of 
sufficient  volume  to  thoroughly  cleanse  it. 
In  fixing  the  trap  care  must  also  be  exercised 
to  see  that  the  overflow  pipe  from  the  fitting 
— where  such  is  separate  from  the  outlet — is 
connected  to  the  inlet  side  of  the  trap  (prefer- 
ably above  the  level  of  the  standing  water), 
and  not  on  the  outlet  side.  Where  the  latter 
is  the  case  the  objects  of  the  trap  are  frustrated, 
as  foul  air  is  able  to  enter  the  house  through 
the  overflow  arm.  When  necessary  the  traps 
must  be  ventilated  (see  "  SIPHONAGE  "). 

The  waste  pipes  of  fittings  which  discharge 
at  some  point  in  the  apartments  in  which 
they  are  fixed  (such,  for  instance,  as  a  house- 
maid's sink  discharging  into  an  adjoining 
slop-hopper,  or  a  washtub  discharging  into  a 
channel  in  the  washhouse  floor)  need  not  be 
trapped,  as  there  is  obviously  nothing  to  trap 
off.  Nor  need  the  waste  pipe  of  a  drip  or 
draw-off  sink  be  trapped  if  no  fouled  water  is 
thrown  into  it,  and  its  point  of  discharge  is 
in  the  open  air,  such  as  over  a  roof  or  lead 
flat,  and  at  some  distance  from  any  likely 
source  of  tainted  air.  It  is,  in  fact,  desirable 
not  to  trust  to  a  trap  in  the  case  of  such  a 
sink,  as  there  are  frequent  occasions  on  which 
the  trap  will  contain  but  little,  if  any,  water. 
It  is  only  when  the  housemaid  is  careless,  and 
permits  the  jug  or  bottle  to  be  filled  to  over- 
flowing, or  does  not  properly  close  the  tap, 
that  such  a  trap  receives  water.  The  waste 
pipe  may,  however,  be  advantageously  fitted 
with  a  flap-valve  at  its  outlet  in  order  to 
exclude  draughts. 

Sanitary  fittings  may  be  roughly  divided 
into  two  classes,  viz.,  (a)  those  for  dis- 
charges consisting  of  purely  waste  water, 
and  (b)  those  for  discharges  charged  with 
excrementitious  matter.  To  the  first  group 
belong  lavatories,  baths,  and  sinks ;  to  the 
second,  water-closets,  housemaids'  slop  sinks 
or  slop-hoppers,  and  urinals.  Waste  pipes 


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from  the  former  must  be  disconnected  from  the 
drains  by  being  discharged  over  gully  traps, 
while  soil  pipes  from  the  second  group  of  fit- 
tings, being  provided  for  the  removal  of  excreta, 
&c.,  must  be  connected  to  the  drains  directly. 

All  sanitary  fittings  should  be  fixed  in 
suitable  apartments.  Convenience  must,  of 
course,  be  studied.  A  slop-hopper,  for  instance, 
must  be  fixed  in  close  though  safe  proximity 
to  the  bedrooms,  as  the  carriage  of  slops  to  a 
distance — possibly  up  or  down  stairs — would 
involve  unnecessary  offence.  The  waste  of 
time  and  exertion  involved  would  also  offer  a 
temptation  to  empty  the  bedroom  slops  into 
the  nearest  bath  or  lavatory  basin.  Safety 
must  not,  however,  be  sacrificed  to  convenience. 
If  a  suitable  apartment  is  not  at  hand  one 
must  be  made  or  adapted,  or  the  fittings 
altogether  dispensed  with.  A  cupboard  or 
dark  out-of-the-way  corner  is  unsuitable  for 
any  sanitary  fitting,  as  in  such  a  position  it 
would  be  sure  to  become  offensive.  The  lighter 
and  more  airy  the  apartment,  the  cleaner  and 
less  offensive  will  be  the  sanitary  apparatus. 
The  apartment  in  which  a  sanitary  fitting  is  to 
be  fixed  should,  therefore,  in  the  first  place, 
be  light  and  well  ventilated.  The  former 
condition  will  render  dirt  and  splashings 
visible,  and  thus  insure  their  removal,  and 
at  the  same  time  tend  to  prevent  them,  by 
enabling  the  user  to  see  what  he  or  she  is 
doing.  Thorough  ventilation  will  maintain 
the  purity  of  the  aerial  contents  of  the  apart- 
ment. This  ventilation,  whenever  possible, 
should  be  independent  of  that  of  the  remainder 
of  the  house. 

A  room  which  provides  the  above  conditions 
will  usually  also  provide  a  second  desideratum, 
namely,  that  one  at  least  of  its  walls  is  an 
external  wall.  This  is  desirable  in  order  that 
the  waste  or  soil  pipe  may  be  immediately 
taken  through  the  wall  to  the  outside  of  the 
house.  Such  pipes,  if  avoidable,  should  not 
be  fixed  inside  the  house,  as,  however  well 
made,  they  are  liable  to  deteriorate  or  to  be 
accidentally  fractured. 

The  walls  and  floors  in  the  immediate 
vicinity  of  sanitary  fittings  should  always  be 


constructed  of  impervious  materials  or  rendered 
non-absorbent  by  being  coated  or  covered  with 
suitable  material,  such,  for  instance,  as  cement, 
tiles  set  in  cement,  slate,  marble,  or  sheet 
lead.  The  actual  materials  made  use  of  must 
necessarily  be  governed  by  such  considerations 
as  cost,  the  nature  and  purposes  of  the 
appliances  and  rooms,  their  positions,  and 
similar  questions,  which  may  vary  in  each 
case,  and  which  must  be  considered  and 
judged  as  they  arise.  The  great  thing  is 
to  prevent  the  retention  of  such  objectionablb 
matter  as  may  be  splashed  over  and  around 
the  fittings.  Woodwork  should,  for  the  same 
reason,  be  avoided  in  connection  with  fittings 
whenever  possible.  If  it  must  be  used  the 
wood  should  be  of  a  hard  and  close-grained 
nature.  It  should  also  be  either  painted  or 
varnished. 

G.  J.  G.  J. 

Sanitary  Inspector,  or  Inspector  of 
Nuisances. — The  statutory  title  of  Sanitary 
Inspector  is  held  in  London  by  virtue  of 
section  108  of  the  Public  Health  (London)  Act, 
1891,  and  that  of  Inspector  of  Nuisances  by 
sections  189  and  190  of  the  Public  Health  Act, 
1875.  The  two  titles  are  for  practical  pur- 
poses synonymous ;  that  of  sanitary  inspector 
is  the  newest  and  more  popular  term.  The 
development  of  the  sanitary  inspector's  office 
has  been  contemporaneous  with  the  growth 
of  public  health  administration.  The  actual 
origin  of  the  office  dates  back  to  the  time  of 
Queen  Elizabeth,  when  an  officer,  called  the 
overseer  of  the  highways,  and  annually  elected 
by  the  vestry  or  highway  authority  of  the 
time,  possessed  power  to  deal  with  nuisances 
thought  to  be  injurious  to  the  health  of  the 
community.  It  was  not,  however,  until  the 
Public  Health  Act,  1844,  was  passed  that  any 
legislative  attempt  was  made  definitely  to 
specialise  the  duty  of  inspection  of  nuisances. 
But  in  the  Nuisances  Removal  Act,  1855,  there  is 
a  clear  recognition  of  the  office,  for  by  section  9 
of  that  Act  local  authorities  are  compelled  to 
appoint  "  sanitary  inspectors."  This  impor- 
tant step  was  further  emphasised  in  the  same 


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year   by  the  Metropolis   Local   Management 
Act,    which,  by   section    133,    provides    that 
inspectors   of   nuisances   shall   be    appointed 
to  supervise  scavenging,  with  powers  to  take 
legal  proceedings,  and  their  duties  are  clearly 
denned  in  other  respects.     The  Public  Health 
Act,  1875,  was  an  amplification  and  codifica- 
tion of  previous  public  health   statutes,  and 
the  Public   Health  (London)  Act,  1891,  was 
designed  to  meet  the  special  conditions  of  the 
Metropolis.     These  two  last-named  Acts  give 
the  present  sanitary  inspector  his  status  in 
public  health  administration.     The  duties  of 
the  ^office   are   many   and   varied,    the    chief 
being   described    as   follows : — by   systematic 
inspection    of   his    district   to    keep    himself 
informed  as  to  any  nuisances  therein  ;  attend 
to  complaints  of   nuisances  or  infractions  of 
the  law  or  by-laws ;  enforce  regulations  made 
in  respect  of  offensive  or  noxious  trades  and 
manufactories ;    supervision   and  examination 
of  food  exposed,  or  in  preparation,  for  sale  for 
human   food ;    seizure   of    unsound   food  and 
obtaining  its  condemnation  by  a  court  of  sum- 
mary jurisdiction ;  to  collect  samples  of  food 
and  drugs  for  analysis,  and  to  take  proceedings 
against  offenders ;  to  supervise  the  execution 
of  works  ordered  by  the  sanitary  authority  for 
the  abatement  of  nuisance ;  enforce  regulations 
for  keeping  animals  in  a  cleanly  state  ;  preven- 
tion of   nuisance   by  smoke ;    supervision   of 
drains  and  sanitary  fittings  of  dwelling-houses, 
work-places,  &c. ;  testing  drains  ;  abatement  of 
overcrowding  ;    regulation  of  lodging-houses  ; 
supervision  of   the   housing   of   the   working 
classes  ;  inspection  of  canal  boats  ;  inspection 
of  and  enforcement  of  regulations  in  respect  of 
dairies,  cowsheds,  and  milkshops ;  regulation 
of  slaughter-houses,  and  maintenance  of  work- 
shops in   a    sanitary  condition,    with   proper 
temperature  and  ventilation.     A  most  impor- 
tant   part    of    their    work    also    is    that    of 
dealing  with  notification  of  infectious  diseases, 
removals  to  hospitals,  disinfection  of  premises, 
and  so  on.     Outside  the  Metropolis  there  is  no 
statutory  qualification  for  the  office ;  any  person 
can   be    legally   appointed    an    inspector    of 
nuisances  under  the  Public  Health  Act,  1875. 


In    London     the     sanitary    inspector     must 
possess  definite  qualification.     By  section  108 
of   the  1891  Act,  since  1895,  every   sanitary 
inspector    appointed    is   required    to   hold    a 
certificate  of  competency  from  such  body  as 
the   Local  Government  Board   may  approve, 
and    such    certificates    are    now  granted    by 
the  Sanitary  Inspectors  Examination  Board. 
The     Eoyal     Sanitary    Institute    also    holds 
examinations    for  sanitary    inspectors,     and 
issues  various  certificates.    In  country  districts 
the  tenure  of  a  sanitary  inspector  is  generally 
for    one    year,    with   annual  re-appointment 
under  the  1875  Act.     But  under  section  108  of 
the  1891  Act,  the  tenure  of  sanitary  inspectors 
rests  with  the  Local  Government  Board,  which, 
by   article  10  of  a  General  Order  dated  8th 
December,     1891,     says,     "  Every     Sanitary 
Inspector    shall   continue    to    hold    office    for 
such  period  as  the  Sanitary  Authority  may, 
subject  to  their  approval,  determine   at   the 
time  of  his  appointment  or  until  he  die  or 
resign,  or  be  removed  by  such  authority,  or 
by  the  Local  Government  Board,  or  be  proved 
to  be  insane."     The  London  County  Council 
now  pays  half  the  salaries  of  many  sanitary 
inspectors     engaged      by     the     metropolitan 
borough   councils,    but   this   financial   aid  to 
local    sanitary  admin stration   does   not  affect 
in    any  way  the    position    or   duties   of   the 
inspector.     By  article  14  of  the  Local  Govern- 
ment  Board    Order,    made    under   the    1891 
Act,  the  salary  of  a  London  inspector  is  such 
as  may  be   approved  by  the  Local   Govern- 
ment   Board,  which,  however,  has  no  power 
to    direct    what    salary   shall    be   paid.      In 
England  the    salary  of   a  sanitary  inspector 
varies   from    £5    per   annum  in  small   rural 
districts   to  ,£350   per  annum.     The  average 
in  the  Metropolis  is  £220.     Scotch  and  Irish 
sanitary     inspectors     are     appointed     under 
different  Acts,  their  tenure  of   office,  qualifi- 
cations,   &c.,    varying     also.       The    highest 
salary  paid  in  Scotland  is  £600  per  annum. 
There  are  about  3,000  sanitary  inspectors  in 
the  United  Kingdom,  and  of  these  probably  a 
sixth  receive  salaries  of  below  £30  per  annum. 
In  London,  superannuation  may  be  granted 


388 


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to  a  sanitary  inspector  under  29  Viet.  c.  31, 
while  in  some  metropolitan  boroughs,  and 
also  in  some  provincial  cities,  power  to  super- 
annuate has  been  obtained  by  special  Acts 
of  Parliament  which  establish  a  contribu- 
tory scheme  of  superannuation  for  municipal 
officers.  But  in  most  rural  and  urban  dis- 
tricts the  sanitary  authority  has  no  power 
to  grant  any  superannuation.  Women  are 
now  appointed  as  sanitary  inspectors,  or 
health  visitors,  mostly  having  special  duties 
in  regard  to  infant  mortality,  infant  feeding, 
domestic  inspection,  &c.  In  districts  where 
a  number  of  sanitary  inspectors  are  employed 
by  the  same  authority  it  is  the  practice  to 
appoint  a  Chief  Sanitary  Inspector,  but  in 
London  the  Chief  Sanitary  Inspector  does  not 
differ  statutorily  from  an  ordinary  inspector ; 
in  urban  districts  the  position  is  slightly 
different,  as  the  1875  Act  gives  power  to 
"  appoint  an  inspector  of  nuisances  and  such 
assistants."  In  rural  districts  the  position 
is  the  same  as  in  London,  one  or  more 
inspectors  being  appointed.  With  the  develop- 
ment of  public  health  administration  neces- 
sitated by  increase  of  population  in  towns, 
urban  areas,  and  metropolitan  districts,  sani- 
tary inspection  has  become  largely  specialised, 
the  duties  of  the  inspector's  office  demanding 
knowledge  of  many  widely  different  subjects, 
ranging  from  drain-pipes  to  meat.  The 
special  circumstances  and  conditions  of  dis- 
tricts govern  the  specialisation,  the  most 
common  special  inspectors  being  meat  in- 
spectors, food  inspectors,  district  and  general 
inspectors,  canal  boat  inspectors,  food  and 
drugs  inspectors,  smoke  inspectors,  workshop 
inspectors,  port  sanitary  inspectors,  and  so 
on.  In  London  the  inspector  has  statutory 
authority  to  serve  preliminary  notices  on  his 
own  initiative,  and  afterwards  to  take  further 
proceedings  as  instructed  by  the  sanitary 
authority.  In  country  districts  the  inspector 
ha.s  no  statutory  power  to  serve  notices  without 
first  being  authorised  on  his  report  in  each 
case  to  the  sanitary  authority.  In  seizing 
meat,  however,  inspectors  can  act  without 
special  authority.  An  inspector  has  to  pro- 


duce his  books  at  the  request  of  the  Medical 
Officer  of  Health,  and,  as  far  as  the  local 
authority  decide  by  resolution,  to  carry  out 
the  instructions  of  the  medical  officer,  but  in 
the  absence  of  such  resolution  the  medical 
officer  has  no  statutory  power  to  give  instruc- 
tions to  the  sanitary  inspector.  The  surveyor 
has  no  authority  over  the  inspector,  nor  can 
such  authority  be  given  by  the  local  authority. 
Sanitary  inspectors  are  an  organised  class  of 
officials.  In  1883  the  "  Sanitary  Inspectors' 
Association"  was  founded  under  the  title  of 
"  The  Association  of  Public  Sanitary  Inspec- 
tors," and  was  incorporated  by  licence  of  the 
Board  of  Trade  in  1891  under  its  present  title. 
The  objects  of  this  organisation  are  largely 
educational,  but  occasionally  representations 
are  made  to  various  public  authorities  in  the 
interests  of  sanitary  inspectors  as  a  whole,  or 
in  special  cases.  It  was  amalgamated  recently 
with  the  National  Union  of  Sanitary  Inspectors. 

C.  E.  A. 

Sanitary  Institute,  Royal. — The  Royal 
Sanitary  Institute  was  founded  in  1876  under 
the  presidency  of  the  late  Duke  of  Northumber- 
land, for  the  advancement  of  all  subjects 
bearing  on  public  health,  and  in  1888  it 
amalgamated  with  the  Parkes  Museum,  \vhich 
was  also  founded  in  1876  as  a  memorial  to 
Dr.  E.  A.  Parkes,  the  first  Professor  of  Hygiene 
at  Netley.  In  the  early  days  of  these  two 
societies,  the  Public  Health  Act,  1875,  had  only 
recently  been  passed,  and  there  was  great  need 
for  elementary  instruction  and  information 
in  the  principles  of  hygiene,  and  it  was  this 
need  that  the  Sanitary  Institute  of  Great 
Britain  (which  was  then  its  title)  set  itself  to 
meet.  One  of  the  first  steps  taken  by  the 
Sanitary  Institute  was  to  establish  examina- 
tions for  local  surveyors  and  inspectors  of 
nuisances.  The  first  examination  was  held  in 
October,  1877,  when  eight  candidates  came 
forward.  These  examinations  gradually 
gained  in  public  estimation,  and  sanitary 
authorities  began  to  recognise  the  advantage 
they  afforded  in  guiding  them  in  the  selection 
of  sanitary  officials.  The  examinations 


389 


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ENCYCLOPAEDIA   OF 


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revealed  the  fact  that  candidates  for  appoint- 
ment as  sanitary  officers  had  considerable 
difficulty  in  obtaining  knowledge  of  the 
principles  of  sanitation,  and  the  council 
established  systematic  courses  of  instruction 
suitable  for  these  officers.  The  examinations, 
which  had  hitherto  been  held  in  London  only, 
were,  in  1889,  extended  to  the  provinces,  so  as 
to  make  them  more  accessible  to  candidates 
living  at  a  distance.  In  the  following  year  the 
training  lectures  for  sanitary  officers  were  also 
extended  to  the  provinces,  and  arranged  in 
conjunction  with  the  county  councils ;  and  in 
the  Public  Health  (London)  Act  the  Institute 
obtained  the  insertion  of  a  clause  requiring 
all  sanitary  inspectors  in  London  appointed 
after  the  1st  January,  1895,  to  hold  a  certificate 
of  qualification.  In  1892  arrangements  were 
made  for  adding  practical  demonstrations  to 
the  courses  of  lectures  for  sanitary  officers, 
and  visits  for  the  students  were  arranged  to 
sewage  works,  waterworks,  trade  premises, 
and  other  places  that  would  be  instructive 
from  a  sanitary  point  of  view.  It  was  pointed 
out  to  the  council,  in  the  year  1895,  that  there 
were  many  persons  who  had  no  intention  of 
becoming  sanitary  officers  who  desired  to 
obtain  a  certificate  from  the  Sanitary  Institute, 
indicating  their  knowledge  of  sanitary  science  ; 
the  council  therefore  thought  it  desirable 
to  arrange  a  syllabus,  which,  although  not 
including  many  technical  subjects  that  an 
inspector  is  required  to  know,  goes  beyqpd 
the  scope  of  the  inspectors'  examination,  as  far 
as  relates  to  practical  sanitation.  The 
examination  is  arranged  so  as  to  be  suitable 
for  foremen  of  works,  builders,  and  those 
engaged  in  allied  trades,  managers  of  property, 
teachers  and  lecturers,  and  others  requiring  a 
thorough  knowledge  of  practical  sanitary 
science.  In  consequence  of  the  report  of  the 
Eoyal  Commission  on  Tuberculosis,  attention 
had  been  directed  to  the  important  question 
of  food  inspection.  There  appeared  to  be  no 
means  available  to  sanitary  inspectors  for 
obtaining  any  information  on  this  subject, 
and  the  council  therefore  organised,  in  con- 
nection with  the  lectures,  demonstrations  with 


regard  to  the  inspection  of  meat  followed  by 
a  practical  examination,  and  special  courses 
have  been  added  adapted  to  the  requirements 
of  army  officers  and  professional  men  who 
come  up  for  the  examinations. 

Further  courses  of  training  and  examina- 
tions have  since  been  established  by  the 
Institute  for  school  teachers,  and  for  health 
visitors  and  school  nurses,  whose  influence 
in  forming  a  hygienic  conscience  in  childhood 
can  effect  much  in  the  advance  of  health  of 
the  nation.  Examinations  of  the  Institute 
are  officially  recognised  by  the  Local  Govern- 
ment Board  and  other  public  bodies.  The 
Institute's  activities  extend  to  the  Colonies, 
where  branch  organisations  are  being  estab- 
lished. Series  of  lectures  on  sanitation  in 
relation  to  the  medical  profession  on  the  sani- 
tation of  industries  and  occupations,  and  on 
weather  and  climate  in  relation  to  health, 
have  been  arranged  by  the  Institute  from 
time  to  time,  sometimes  in  co-operation  with 
other  societies. 

The  Parkes  Museum,  which  is  maintained 
by  the  Institute,  contains  a  collection  of 
typical  appliances  relating  to  sanitation  and 
public  health.  It  is  used  by  the  Medical 
Schools  and  Colleges  of  the  London  Hos- 
pitals for  their  classes  for  the  Diploma  in 
Public  Health,  and  is  recognised  by  the 
Science  and  Art  Department  in  connection 
with  their  classes,  and  the  class  visits  paid 
by  the  students  to  the  museum  may  be 
counted  as  a  class  attendance  for  the 
purpose  of  the  examination  grant.  The 
museum,  besides  being  a  most  important 
adjunct  to  the  work  of  the  Institute,  forms 
the  basis  of  a  large  portion  of  the  teaching  in 
practical  hygiene  that  is  given  in  London. 
Visits  are  frequently  made  to  the  museum  by 
representatives  from  the  Colonies  and  the 
Continent,  with  the  object  of  obtaining 
information  for  establishing  or  enlarging 
similar  museums.  The  Institute  has  a  large 
sanitary  library  which  has  been  added  to  by 
the  transfer  to  it  of  other  similar  collections, 
and  now  forms  one  of  the  best  sanitary 
libraries  in  London.  The  Transactions  of 


390 


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MUNICIPAL   AND    SANITAKY   ENGINEEEING. 


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the  Institute  were  first  issued  to  the  members 
in  1879,  and  for  many  years  consisted  of 
an  annual  volume  ;  afterwards  it  was  thought 
desirable  to  give  the  information  more  fre- 
quently, and  in  1894  they  were  issued  as  a 
quarterly  journal,  and  in  1905  it  was  altered 
to  a  monthly  publication. 

Periodical  congresses,  attended  by  the 
members  and  representatives  of  public  bodies, 
are  held  in  different  parts  of  the  United  King- 
dom. In  connection  with  these  meetings, 
exhibitions  of  sanitary  appliances  are  held. 
Conferences  on  special  subjects  have  been 
convened  in  London  from  time  to  time. 
Meetings  of  the  members  for  the  deliberation 
on,  and  discussion  of,  subjects  relating  to 
public  health  are  held  throughout  each  year 
in  London  and  in  provincial  centres,  and 
are  also  arranged  from  time  to  time  in  the 
Colonies. 

A  special  committee  is  appointed  by  the 
council  to  consider  all  Bills  brought  before 
Parliament  that  bear  upon  public  health, 
and,  on  their  recommendation,  petitions  and 
amendments  are  submitted  to  both  Houses  and 
to  the  supporters  of  the  Bills.  By-laws  of  the 
London  County  Council,  water  regulations,  and 
other  matters  of  public  sanitary  interest  are 
carefully  watched  and  discussed,  and  experi- 
ments and  investigations  are  conducted  to 
elucidate  points  under  discussion.  There  is  also 
an  expert  committee  for  judging  and  making 
awards  to  sanitary  appliances  exhibited  at 
the  exhibitions  held  by  the  Institute.  These 
awards  are  made  on  a  uniform  system  so  as 
to  serve  as  a  guide  to  the  public  in  selecting 
sanitary  apparatus. 

In  the  course  of  each  year  some  500 
meetings  are  organised  in  order  to  carry  out 
its  various  functions. 

The  various  branches  of  the  work  are,  in 
short : — The  Museum,  containing  a  collection 
of  typical  sanitary  appliances ;  the  Library ; 
Students'  Lectures  and  Examinations;  the 
Monthly  Journal  of  Proceedings ;  Meetings 
for  Discussions  ;  Congresses ;  Exhibitions  ; 
Research  Work  and  Experimental  Work ; 
Parliamentary. 


The  Institute  has  carried  on  its  work 
entirely  without  the  aid  of  public  funds,  but  a 
portion  of  the  Berridge  Bequests,  amounting 
to  £10,000,  was  allotted  to  the  Institute,  and 
some  years  later  it  had  a  legacy  of  .£5,000 
left  by  Mr.  Rogers  Field. 

The  aim  which  the  Royal  Sanitary  Institute 
has  before  it  is  to  produce  a  higher  standard 
of  health  and  the  reduction  of  the  death  rate 
and  sickness  rate  throughout  the  country.  It 
seeks  to  accomplish  this  (a)  by  dealing  with 
the  question  of  the  rearing  of  infants, 
their  proper  feeding,  and  the  removal  of  the 
various  causes  which  affect  infant  mortality. 
(b)  By  endeavouring  to  secure  the  purity  of 
the  milk  supply  and  the  food  supplies, 
especially  meat,  (c)  By  advancing  measures 
for  the  better  housing  of  the  working  classes, 
and  also  by  promoting  a  proper  use  of 
materials,  sanitary  appliances,  and  drainage 
arrangements  in  better  class  houses,  (d)  By 
dealing  with  the  various  causes  of  pre- 
ventible  diseases  and  the, -proper  isolation  of 
infectious  diseases,  especially  the  question  of 
tuberculosis. 

By  means  of  its  pioneer  work  in  teaching 
and  examination,  the  discussion  of  various 
questions  and  problems  that  arise,  and  other 
practical  efforts,  the  Institute  has  become 
an  important  factor  in  the  advancement  of 
hygiene  and  public  health  in  Great  Britain 
and  the  Colonies,  and  its  steady  growth  is 
an  indication  of  the  increasing  attention  given 
to  this  science.  E.  W.  W. 

School  Hygiene  embraces  a  due  regard 
to  every  circumstance  that  may  react  for 
good  or  evil  upon  the  physical  and  mental 
health  and  development  of  the  school  child, 
Thus  the  site  and  construction  of  the  school 
premises,  the  ventilating,  lighting,  warming, 
and  cleaning  of  school  class-rooms,  cloak- 
rooms, corridors,  and  dormitories,  the  provi- 
sion of  suitable  school  furniture,  and  of 
washing,  water-closet,  and  urinal  accommoda- 
tion, must  all  insure  the  best  possible  hygienic 
environment  for  the  scholars,  and  present  an 
object  lesson  of  cleanliness  and  of  scrupulous 


391 


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ENCYCLOPAEDIA   OF 


SCH 


regard  to  all  sanitary  demands.     Regard  for 
the  personal  hygiene  and  physical  development 
of  the  scholar  is  no  less  important ;  and  the 
prompt  detection  of  physical  defects  and  of 
communicable  and  other  disease  is  of  prime 
concern.     The  demands  of  school  hygiene  also 
embrace  the  teaching  and  training  of  scholars 
in  the  laws  of  health,  in  order  to  promote  the 
formation  of  healthy  habits  and  the  "  health 
conscience"  which,  along  with  the  practical 
advice    given,  will  fit  them  to   lead  healthy 
lives  and  to  guard  the  health  interests  of  their 
offspring.    Although  Hygiene  is  not  yet  taught 
as  a  subject  in  our  elementary  schools,  the 
Educational  Code  now  definitely  "  recognises  " 
one  important  branch  of  it,  namely,  Cookery 
and  Housewifery.     These  matters,  including 
infant  care  and  feeding,  should  certainly  be 
constituted  a  compulsory    practical    training 
course  for  the  older  girls,  as  suggested  by  the 
Royal  Commission  on  Physical  Deterioration. 
The  extent  to  which  the  home  influences  and 
the  school  influences,  respectively,  are  respon- 
sible for  physical  defects  and  the  prevalence 
of  diseases  among  school  children  is  a  matter 
which  may  ultimately  be  determined,  but  for 
the  present  it  is  imperative  to  avail  ourselves 
of  the  unrivalled  opportunities  which  school 
attendance  presents  for  the  detection  of  these 
disabling  conditions.     There  can  be  no  gain- 
saying that  even  at  the  present  day  the  school 
remains  the  chief  centre  of  infection  among 
the  community.     The  circumstance  that  the 
most  susceptible  units  of  the  population  are 
daily  assembled  in  close  contact  is  responsible 
for  this  ;  and  the  closest  co-operation  of  the 
school  teachers,  medical  inspectors,  and  medi- 
cal officers  of  health  is  necessary  to  meet  the 
legitimate    demands    of   parents    that  school 
attendance   shall   be    made   as   safe   for   the 
children  as  it  is   possible  to  make  it.     The 
problem  of  promoting  the  physical  and  moral 
hygiene   of   the   community   does   not    grow 
easier  day  by  day  with  the  increasing  concen- 
tration of  population  of  large  urban  commu- 
nities, and  all  are  agreed  that  there  exists  a 
sad  need  for  the    general   raising    of   ideals 
among   the   people.     It   is    upon    school   in- 


fluences that  we  must  mainly  base  our  hope 
and   expectation    of    future   improvement   in 
this   respect.     It   is   not,    however,  on   these 
grounds  alone  that   the  State    has    done  so 
much  to  promote  school  hygiene.     The  fact 
has   long    been    recognised   that   the   fullest 
regard  for  the  bodily  health  of  the  child  is 
necessary  to  obtain  the  best  mental  reaction  ; 
and  so  school  methods,  carefully  designed  to 
meet  the  physiological  demands  of  a  mentally 
and    physically   developing    child,    determine 
educational  efficiency ;  thus  it  is  realised  that 
school  hygiene  is  necessary  for  the  development 
of  the  best  type  of  citizen — the  best  mentally, 
the   best   morally,    and   the    best   physically. 
Systematic  courses  of  instruction  for  teachers 
have    accordingly   been    arranged    by   many 
educational   authorities,   and    the   increasing 
efforts  of  the  London  County  Council  to  meet 
this   need   in   London   during   the   past   few 
years   is    a   noteworthy   sign    of    the    times. 
Moreover,  the  recently  issued  set  of  regula- 
tions of  the  Board  of  Education,  in  reference 
to    school   teachers,   introduces   for   the   first 
time  a  compulsory  hygiene  course  and  a  com- 
pulsory examination  in  hygiene  for  all  students 
in  training  colleges  who  intend  to  be  teachers 
in  elementary  schools.  The  medical  inspection 
of  school  children  which  is  now  in  operation 
throughout  the  country  may  also  claim  both 
physical  and  educational  merits.     It  aims  at 
detecting  and  removing  physical  disabilities 
which  in  no  small  measure  determine  physical 
health  and  development,  and  it  is  an  additional 
method   of   endeavouring   to   put   the  school 
child   into   the   most   suitable    state   for   his 
training.     Moreover,  it  is  but  the  logical  con- 
sequence of  the  State  taking  over  the  school 
education  of  the  child  from  the  civic  stand- 
point that  the  State  requires  efficient  citizens 
and  the  child  is  not  the  property  of  the  parent 
alone.     In  the  scheme  of  medical  inspection 
the   teachers   are    generally   asked   to   select 
those  children  for  special  medical  examination 
who  show  any  marked  signs  of  departure  from 
the  normal ;  loyally  to  assist  generally  in  the 
larger  scheme  and  organisation  of  medical  in- 
spection ;  and  by  exercising  a  tactful  influence 


392 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


SEW 


over  parents  to  assist  in  obtaining  a  remedy 
for  their  children's  defects.  It  need  hardly  be 
said  that  the  teachers  have  responded  loyally 
to  these  demands.  To  whatever  extent  medical 
inspection  may  lead  to  the  detection  and  alle- 
viation of  physical  defects  in  school  children, 
to  a  corresponding  extent  will  children  gain 
in  general  health  and  development,  better 
results  will  be  obtained  from  the  teaching  at 
school,  the  more  healthy  and  physically  fit  child 
will  be  less  a  drag  upon  the  resources  of  the 
family  and  the  State,  and  posterity  will  benefit 
from  a  healthier  stock.  The  results  of  the 
work  already  undertaken  in  this  country,  of 
course,  vary  with  the  schools  inspected,  but 
the  figures  range  from  10  %  of  unfit  children 
in  the  better  class  schools  to  more  than  30  % 
in  schools  drawing  scholars  from  the  slums  of 
large  cities.  Supplemented  by  trained  school 
nurses  and  health  visitors,  who  will  penetrate 
into  the  more  necessitous  homes,  medical 
inspection  will  develop  into  a  potent  educative 
force  in  preventive  medicine  and  in  raising 
the  level  of  social  well-being.  H.  R.  K. 

Separator,  Rain-water, — An  appliance 
made  use  of  for  discarding  the  first  flow  of 
water  from  roofs  and  other  surfaces  wrhere 
rain-water  is  collected  for  storage  and  use ; 
this  portion  of  water  being  always  more  or 
less  polluted  by  the  washings  of  soot,  bird 
excrement,  and  other  impurities.  The  appa- 
ratus consists  of  a  vessel  into  which  the 
rain-water  is  directed  before  passing  into  the 
storage  tank,  &c.,  so  arranged  that  the  first 
portion  of  the  water  is  collected  and  emptied 
to  waste  so  soon  as  the  chamber  provided  for 
that  purpose  is  full.  This  water  having  been 
tipped  out,  the  remainder  of  the  rainfall  is 
allowed  to  enter  the  storage  tank.  When  the 
flow  of  water  has  ceased,  the  vessel  in  which 
the  soiled  water  is  collected  returns  automati- 
cally to  its  original  position. 

Septic  Tanks.    (See  "  SEWAGE  DISPOSAL.") 


Settling    Tanks.     (See     "  SEWAGE    DIS- 
POSAL.") 


Sewage  and  Effluents,  Analysis  of.— 

Sampling  —  Analysis — Total  Solids  —  Organic 
Matter — Albuminoid  Ammonia  —  Products  of 
Oxidation — Standards  of  Purity  for  Effluents. 

SAMPLING. — The  analysis  of  sewage  and 
sewrage  effluents  is  undertaken  in  order  to 
ascertain  the  percentage  purification  produced 
by  the  process  employed,  or  proposed  to  be 
employed,  in  treating  the  sewage.  Effluents 
may  also  be  examined  to  ascertain  whether 
they  pass  a  given  standard,  whether  they 
vary  according  to  modifications  of  treatment, 
or  to  learn  whether  an  effluent  which  is 
satisfactorily  treated  by  a  given  plant  in  times 
of  normal  flow  is  brought  to  the  required 
degree  of  purification  when  the  volume  of 
sewage  rises  above  the  normal.  In  sampling 
sewage  several  points  have  to  be  considered, 
the  most  important  of  which  is  the  great 
variation  in  the  quantity  and  quality  of  the 
sewage  at  different  times  during  the  day  and 
night.  There  is,  of  course,  also  a  very  great 
difference  in  the  quantity-  and  quality  of  the 
sewage  according  to  the  rainfall,  and  again  the 
season  of  the  year  and  the  temperature  have  a 
great  effect  on  the  degree  of  decomposition 
which  the  sewage  may  have  undergone  on  its 
way  to  the  sewage  works.  There  are  naturally 
also  minor  causes  which  may  produce  consider- 
able temporary  alterations  in  the  sewage,  such 
as  the  flushing  of  the  sewers,  washing  the 
streets,  the  discharge  of  accumulations  of 
liquor  from  breweries,  tanneries,  paper 
factories  and  the  like.  The  quantity  and 
composition  of  town  sewage  varies  from  hour 
to  hour.  The  strongest  and  most  polluted 
sewage  comes  from  the  houses  from  about  8 
to  10  in  the  morning,  and  the  time  taken  for 
this  to  reach  the  works  will  depend  on  the 
distance  and  the  fall.  After  10  in  the  morning 
the  liquids  and  solids  entering  the  sewer  are 
more  diluted,  and  in  the  evening  and  night 
time  the  volume  and  the  impurities  are  both 
very  much  reduced.  As  the  bulk  of  the  sewage 
varies,  so  must  the  bulk  of  the  samples  that 
are  being  collected,  and  samples  should  be 
taken  hourly  or  half-hourly  and  mixed,  and 
they  should  be  placed  in  a  bucket  kept  cool 


393 


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ENCYCLOPAEDIA   OF 


SEW 


with  ice.  It  will  generally  be  found  necessary 
to  break  up  the  solids  by  a  plunger,  which  may 
be  made  by  nailing  a  disc  of  tin,  perforated 
with  holes,  on  to  the  end  of  a  broom-stick. 
If  the  analyses  are  being  undertaken  with  a 
view  of  learning  the  percentage  purification 
attained  by  the  process  of  treatment  in  use, 
samples  of  the  effluent  may  be  collected  at  the 
same  time,  taking  as  above  mentioned  hourly 
or  half-hourly  samples,  in  proportion  to  the 
volume  of  flow  from  time  to  time.  By  starting 
to  take  the  samples  of  the  effluent  at  a  given 
time  after  the  sampling  of  the  crude  sewage 
is  begun,  it  may  be  possible  to  obtain  repre- 
sentative samples  of  the  crude  sewage  and 
effluent  which  actually  correspond — that  is  to 
say  that  the  effluent  is  actually  identical  with 
the  crude  sewage  as  the  samples  were  taken 
from.  In  any  case  there  ought  to  be  little 
difference  between  the  chlorine  figures  of  the 
crude  sewage  and  the  effluent  (both  being 
determined  on  mixed  samples  after  filtration 
through  filter-paper).  If  the  chlorine  figures 
do  not  correspond  very  closely  it  brings  us  to 
the  immediate  conclusion  that  the  samples  of 
crude  sewage  and  effluent  are  certainly  not 
identical  or  strictly  comparable,  while  if  the 
chlorine  figures  do  correspond  we  cannot 
conclude  for  certain  that  the  samples  are 
comparable,  though  they  are  probably  so. 
Should  there  be  a  discrepancy  of  more  than 
1  grain  of  chlorine  per  gallon,  the  samples 
should  not  be  taken  as  representative,  and 
should  be  discarded,  or  the  results  should  be 
calculated  to  a  common  chlorine  standard,  and 
only  employed  as  part  of  a  series  extending 
over  several  more  days.  In  any  case,  the 
sampling  should  be  continued  over  a  period 
of  three  days  of  normal  (dry  weather)  flow, 
and  if  storm-water  has  also  to  be  treated,  as  is 
generally  the  case,  a  second  series  of  samples 
(extending  over  three  days)  should  be  collected 
as  described  above,  during  rainy  weather,  and 
submitted  to  analysis  in  the  same  way.  In 
analysing  sewage,  partly-treated  sewage,  or 
sewage  effluent,  it  is,  as  has  already  been 
mentioned,  of  the  greatest  importance  to  make 
the  analyses  as  soon  as  possible  after  the 


collection  of  the  samples,  which  should  be 
kept  cool  in  ice.  It  will  readily  be  understood 
that  such  samples,  containing,  as  they  always 
must,  great  numbers  of  active  bacteria  in  a 
liquid  containing  organic  matter  in  process  of 
breaking  down  and  alteration,  are  far  more 
liable  to  undergo  rapid  alteration  in  composi- 
tion than  potable  waters,  which  contain  far 
less  organic  matter  and  comparatively  few 
bacteria.  The  rate  at  which  this  alteration 
will  proceed  in  sewage  and  effluents  is  well 
shown  by  examining  a  fresh  sample  and 
repeating  the  analysis  after  a  couple  of  days. 

ANALYSIS. — The  analysis  of  sewage,  partly 
treated  sewage,  and  effluents  is  carried  out, 
very  much  on  the  same  lines  as  a  water 
analysis,  except  that  it  is  necessary  to  use 
different  quantities  for  certain  of  the  operations. 
The  estimations  which  it  is  usually  customary 
to  make  are  as  follows  : — 

TOTAL  SOLIDS  may  conveniently  be  esti- 
mated on  an  amount  varying  from  100 
to  250  c.c.  MINERAL  SOLIDS  are  obtained 
by  cautiously  igniting  the  total  solids  and 
recarbonating,  as  in  water  analysis.  The 
Loss  ON  IGNITION  is  ascertained  by  sub- 
tracting the  mineral  solids  (re-carbonated) 
from  the  completely  dried  total  solids.  The 
loss  on  ignition  is  a  valuable  figure,  but,  as  it 
is  liable  to  vary  very  much  in  the  crude 
sewage,  an  average  of  several  samples  should 
be  taken.  In  partially  treated  sewage  it  will 
vary  less,  and  in  effluents  it  is  even  more 
constant  still,  and  regular  determinations  are 
of  great  assistance  in  learning  whether  the 
treatment  is  uniform  and  successful. 

The  CHLORINE  ESTIMATION  is  carried  out 
as  in  water  analysis,  except  that  it  is  best  to 
remove  suspended  matters  first,  by  filtration, 
and  if  the  water  is  alkaline  or  acid  it  should  be 
neutralised  before  titrating  with  the  standard 
silver  nitrate  solution.  The  standard  silver 
solution  should  be  kept  in  a  brown  bottle  and 
placed  in  a  dark  cupboard  when  not  in  actual 
use.  The  value  of  the  chlorine  estimation  lies 
chiefly  in  the  fact  that  by  its  determination 
we  are  able  to  identify  an  effluent  with  the 
sewage  it  was  produced  from.  That  is  to  say, 


394 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


SEW 


if  in  a  series  of  sewage  samples  and  samples 
of  effluent  the  average  chlorine-contents  are 
the  same,  or  very  nearly  the  same,  we  know 
that  the  effluent  in  all  probability  corresponds 
to  the  sewage,  and,  therefore,  comparisons  to 
ascertain  percentage  purification  may  be 
logically  made,  whereas  if  the  chlorine  figures 
exhibit  a  sensible  difference  such  a  comparison 
might,  and  probably  would,  be  erroneous.  It 
is  hardly  necessary  to  say  that  the  chlorine 
figure  is  quite  unaffected  by  any  process  of 
treatment  (short  of  adding  chlorides),  and, 
therefore,  any  chlorides  present  in  the  raw 
sewage  remain  throughout  the  treatment  and 
appear  in  the  effluent  neither  diminished  nor 
increased,  except  that  a  "  smoothing "  or 
equalising  action  takes  place  as  the  richer 
sewage  that  comes  in  the  morning  becomes 
gradually  mixed  with  the  diluted  portions 
that  come  in  the  afternoon  and  night.  It  will 
be  clear  that  a  high  figure  for  chlorine  in  a 
sewage  will  usually  indicate  a  strong  sewage, 
and  in  the  same  way  an  effluent  which  gives 
a  high  figure  for  chlorine  was  probably 
produced  from  a  strong  sewage ;  but  whereas  a 
high  figure  for  chlorine  in  a  potable  water 
would  be  a  bad  sign,  a  high  figure  for  chlorine 
in  an  effluent  has  no  significance  beyond  that 
mentioned  above. 

ORGANIC  MATTER. — The  organic  matter  in  a 
sewage  is  partly  in  solution  and  partly  in 
suspension.  Both  of  these  are  more  or  less 
accurately  measured  by  the  estimation  of  the 
loss  on  ignition  previously  mentioned.  It  is, 
however,  customary  to  estimate  the  "  oxygen 
absorbed "  and  albuminoid  ammonia,  which 
taken  in  conjunction  afford  valuable  means  of 
defining  the  organic  matter  present.  In  a 
liquid  so  much  richer  in  organic  matter  than 
an  ordinary  potable  water,  it  is  necessary  either 
to  use  different  standard  solutions  to  those 
employed  in  water  analysis,  or  to  work  on 
much  less  quantities. 

For  the  determination  of  THE  OXYGEN 
ABSORBED  in  sewage  and  effluents,  it  is  con- 
venient to  use  100  c.c.  of  sample,  and  a 
standard  permanganate  solution  of  double 
the  strength  usually  employed— care  must 


be  taken  to  add  more  permanganate  if  the 
colour  becomes  pale.  It  is  best  to  adopt  the 
4-hour  period  for  the  permanganate  to  act 
on  the  organic  matter,  but  even  then  a  great 
deal  of  organic  matter  will  remain  totally 
unaffected.  For  example,  particles  of  straw, 
undigested  muscular  fibre,  and  the  like,  are 
almost  entirely  unchanged.  It  would  probably 
be  better  to  employ  one  of  the  hot  moist 
combustion  processes  which  are  in  favour 
abroad,  but  which  do  not  appear  to  be  much 
used  in  this  country.  The  amount  of  "  oxygen 
absorbed"  in  a  fresh  crude  sewage  is  very 
variable  and  may  be  from  as  low  as  a  grain 
per  gallon  up  to  10  grains  or  more.  In  a 
well-treated  effluent  there  should  be  a  reduc- 
tion of  70  to  80  °/0  on  the  figure  for  oxygen 
absorbed. 

ALBUMINOID  AMMONIA. — This  is  determined, 
as  in  a  potable  water,  by  distillation  with 
alkaline  permanganate.  Some  workers  prefer 
to  operate  on  as  small  a  quantity  as  5  or 
10  c.c.  and  to  dilute  it  to.  500  c.c.  But  it 
is  better  to  wrork  on  500  c.c.  and  (having 
removed  the  saline  ammonia  by  distillation 
in  the  ordinary  way)  to  collect  all  the  albu- 
minoid ammonia  in  a  flask,  and,  instead  of 
Nesslerising,  to  titrate  the  ammoniacal  dis- 
tillate with  standard  sulphuric  acid,  using 
cochineal  as  an  indicator.  As  the  saline 
ammonia  has  to  be  distilled  off  it  may  be 
estimated,  and  it  will  be  found  that  whereas 
a  crude  sewage  may  contain  from  2  to  6  grains 
per  gallon,  a  well-treated  effluent  will  rarely 
contain  as  much  as  1  grain.  At  the  same 
time  the  amount  of  saline  ammonia  in  a 
sewage  or  an  effluent  is  a  matter  of  compara- 
tively small  importance.  The  albuminoid 
ammonia  on  a  crude  sewage  is  rarely  more 
than  1  grain  per  gallon,  and  in  an  effluent  is 
about  O'l,  but  should  not  be  more.  As  men- 
tioned before,  in  the  "  oxygen  absorbed " 
process  some  of  the  organic  matter  may 
escape  complete  decomposition,  but  this  is  not 
the  case  in  the  estimation  of  albuminoid 
ammonia,  as  the  energetic  action  of  the 
permanganate  in  presence  of  alkali  and 
the  prolonged  boiling  may  be  relied  on  to 


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decompose  any  organic  matter  and  to  liberate 
as  ammonia  any  combined  nitrogen  that  is 
present. 

PRODUCTS  OF  OXIDATION. — When  sewage  is 
treated  most  of  the  suspended  matters  are 
removed  either  by  natural  sedimentation  or 
by  precipitation,  or  are  mechanically  detained 
in  filter  media.  The  oxidisable  matters  are 
altered  and  the  nitrogenous  matters  are  con- 
verted into  nitrites  and  nitrates,  while  the 
non-nitrogenous  matter  is  probably  chiefly 
converted  into  carbonic  acid  gas,  marsh 
gas,  &c.,  and  to  a  considerable  extent  escapes 
into  the  atmosphere.  There  is,  therefore,  no 
means  of  ascertaining  in  an  effluent  what  has 
become  of  the  non-nitrogenous  organic  matter 
which  was  originally  contained  in  the  raw 
sewage,  but  in  the  case  of  the  nitrogenous 
matter  a  considerable  proportion  is  oxidised 
to  nitrates,  and  the  estimation  of  nitrates 
should  always  be  made  in  effluents,  as  the 
presence  of  a  fair  proportion  of  nitrates  is 
most  important  as  showing  that  true  purifica- 
tion has  been  effected.  Crude  sewage  very 
seldom  contains  any  nitrates  or  nitrites. 
They  may  begin  to  appear  at  some  point  in 
the  process,  but  they  are  always  present  in  a 
properly  purified  effluent.  As  a  rule  the 
oxidised  nitrogen  in  an  effluent  is  all  present 
as  nitrate,  only  traces  of  nitrites  being  present. 
It  is  as  well  to  test  for  the  presence  of  nitrites 
(as  directed  under  the  "  ANALYSIS  OF  WATER  "), 
but  it  will  be  very  rarely  necessary  to  estimate 
them.  An  effluent  will  yield  the  reaction  for 
nitrites  if  it  is  kept  for  a  few  days  in  a  closed 
bottle  before  analysing,  but  it  very  rarely 
yields  any  reaction  for  nitrites  when  fresh. 
The  estimation  of  nitrates  may  be  carried  out 
as  described  under  "  WATER  ANALYSIS,"  and 
the  phenol-sulphuric  acid  method  will  be  found 
to  give  satisfactory  results. 

STANDARDS  OF  PURITY  FOR  EFFLUENTS. — 
As  soon  as  it  became  customary  to  treat 
sewage,  those  engaged  in  its  treatment 
naturally  desired  to  know  whether  the 
effluents  they  produced  were  satisfactory,  and 
also  how  their  results  compared  with  those 
obtained  at  other  places  by  similar  or  different 


methods.  Probably  the  appearance  (colour 
and  freedom  from  suspended  matter)  and 
absence  of  smell  were  the  characters  that 
were  considered  in  early  days.  Later  on  it 
became  the  practice  to  place  samples  of  the 
effluent  in  open  and  closed  bottles  and  to  note 
the  appearance  and  smell  after  keeping  for 
some  time.  If  the  samples  remained  sweet 
as  regards  smell  and  did  not  putrefy  they  were 
considered  satisfactory.  If  a  green  growth 
occurred,  it  was  (and  is)  regarded  as  a  favour- 
able sign.  Such  a  growth  is  due  to  harmless 
alga3,  and  is  unlikely  to  develop  except  in  a 
fairly  well  purified  effluent.  At  a  later  date, 
when  the  science  of  bacteriology  began  to 
receive  attention,  it  became  customary  to 
incubate  samples  of  effluent,  that  is,  to  place 
them  in  a  chamber  constantly  maintained  at 
blood-heat,  and  to  note  whether  they  remained 
sweet  or  suffered  decomposition.  As  the 
science  of  bacteriology  progressed  it  became 
apparent  that  the  older  methods  of  sewage 
treatment,  wrhich  aimed  chiefly  at  the  removal 
or  precipitation  of  the  suspended  matters,  did 
not  produce  a  sufficient  effect  on  the  organic 
matter  in  suspension,  which  passed  on 
throughout  the  process  and  appeared  in  the 
effluent  and  caused  it  to  "go  bad,"  or  suffer 
a  secondary  decomposition,  accompanied  by 
smell  and  by  the  growth  of  sewage  fungus  in 
streams  into  which  the  effluent  discharged,  at 
the  same  time  often  causing  the  death  of  fish 
in  such  streams  where  the  volume  of  the 
effluent  was  great  enough  to  destroy  the 
"  dissolved  oxygen,"  without  which  fish 
cannot  live.  Later  on  it  became  customary 
to  examine  the  number  and  nature  of  the 
bacterial  population  of  sewage  arid  effluents 
and  to  analyse  sewage  and  effluents.  It  is 
now  known  that  whereas  sewage  contains  vast 
numbers  of  many  different  species  of  bacteria, 
effluents  usually  contain  far  fewer,  and  that 
even  if  disease  bacteria  exist  in  a  sewage 
(such,  for  example,  as  the  drainage  from  a 
typhoid  hospital),  it  is  very  seldom  that  they 
can  be  isolated  in  the  effluent,  and,  moreover, 
that  the  number  of  cases  wherein  disease  is 
contracted  from  an  effluent  are  so  rare  as  to 


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lead  to  the  conclusion  that  the  disease  bacteria 
in  sewage  must  to  a  large  extent  be  destroyed 
either  by  the  other  bacteria  with  which  they 
are  associated,  or  by  some  chemical  effect  of 
the  various  treatments  in  general  use.  It 
eventually  was  recognised  that  a  chemical 
analysis  was  more  useful  than  a  bacterio- 
logical examination  in  showing  whether  a 
given  sewage  treatment  was  effectual.  Putting 
the  sewage  problem  into  the  simplest  terms,  the 
question  before  authorities  resolves  itself  into 
this  :  How  to  treat  their  sewage  in  the  cheapest 
manner  consistent  with  the  production  of  an 
effluent  which  will  not  give  rise  to  a  nuisance. 
Various  standards  have  been  suggested,  and 
some  have  been  definitely  adopted  in  certain 
districts.  It  will  be  obvious  that  an  effluent 
that  is  to  be  run  into  the  sea  or  into  a  large 
river,  which  is  not  used  as  a  source  of  drinking 
water,  need  not  be  as  pure  as  one  that  has  to 
be  run  into  a  very  small  stream,  or  a  river 
from  which  a  water  supply  has  to  be  taken 
further  down  its  course.  The  question  of 
standards  of  purity  for  effluents  was  discussed 
at  a  meeting  of  the  Society  of  Public  Analysts, 
when  a  paper  on  this  subject  was  read  by  the 
present  writer  in  1898,  and  various  opinions 
were  expressed  by  well-known  analysts.  The 
report  of  the  paper  and  the  discussion  will 
be  found  in  the  Analyst  for  1898,  page  198. 
At  this  time  the  writer  laid  stress  on  the 
point  that  a  properly  purified  effluent  should 
conform  to  a  standard  expressed  in  figures 
showing  the  absence  of  more  than  certain 
quantities  of  "oxygen  absorbed"  and  albu- 
minoid ammonia,  and  that  there  should  be 
present  not  less  than  a  certain  proportion  of 
nitrates.  These  figures  were  founded  on  the 
analyses  and  observation  of  a  large  number 
of  effluents,  which,  while  they  conformed  to 
the  suggested  standard,  were  found  to  keep 
well,  in  open  or  closed  vessels,  without  suffer- 
ing putrefactive  changes.  Various  "  standards 
of  purity  "  for  effluents  have  been  proposed, 
and  some  have  been  adopted,  by  bodies  such 
as  the  Thames  Conservancy,  the  Derbyshire 
County  Council,  &c.  The  Mersey  and  Irwell 
Joint  Piivers  Board's  standard,  which  is  a  typical 


one  adopted  by  other  rivers  boards,  requires 
the  following :  Oxygen  absorbed  in  4  hours 
at  80°  F.  =  1  grain  per  gallon  ;  albuminoid 
ammonia  =  O'l  grain  per  gallon.  All  the 
standards  are  designed  to  secure  the  same 
result,  namely,,  the  production  of  as  good 
and  as  uniform  an  effluent  as  possible. 

C.  G.  M. 

Sewage  Disposal, — Object  of  Purification 
and  Composition  of  Sewage — Standards  of  Purity 
in  Effluents — Screening,  Detritus,  and  Sedimen- 
tation Tanks — Septic  Tanks,  and  other  Forms  of 
Tank — Chemical  Precipitation — Contact  Beds — 
Percolating  Beds — Removal  of  Suspended  Matter 
in  Effluents — Treatment  on  Land — Selection  of  a 
System  of  Treatment. 

THE  OBJECT  or  SEWAGE  PURIFICATION  is  the 
removal  of  the  suspended  matters  and  the 
complete  oxidation  of  the  organic  matter  and 
ammonia  in  solution.  In  the  treatment  of 
sewage  on  land  and  on  filters  the  process  of 
oxidation  is  now  believed  to  be  mainly  of  a 
biological  nature,  but  although  a  large  amount 
of  experimental  and  research  work  has  been 
done,  there  are  many  scientific  points  con- 
nected with  the  purification  of  sewage  which 
still  require  explanation.  Provided  the  neces- 
sary expense  is  incurred,  it  is  possible  to  carry 
the  work  of  purification  to  any  degree  required 
either  upon  land  or  on  specially  prepared 
bacteria  beds,  and  in  both  cases  the  work  done 
is  effected  chiefly  by  the  activity  of  various 
micro-organisms. 

THE  COMPOSITION  OF  SEWAGE  differs  widely 
in  different  localities.  When  of  average 
strength  it  contains  about  100  grains  of  solid 
matter  per  gallon,  of  which  about  one-third  is 
in  suspension  and  two-thirds  in  solution.  The 
mixture  usually  consists  largely  of  saline 
matter  in  solution,  with  nitrogenous  and  car- 
bonaceous organic  matter  in  solution  and 
suspension,  and  varying  amounts  of  sand, 
road  grit,  or  other  mineral  matters.  The 
strength  of  a  sewage  has  necessarily  an 
important  bearing  upon  the  nature  of  the 
treatment  required  for  its  purification,  and 
since  the  process  is  largely  one  of  indirect 


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oxidation  through  the  agency  of  bacteria,  the 
amount  of  oxygen  required  for  bringing  about 
its  complete  oxidation  should  be  ascertained. 
This  splitting  up  of  the  organic  matter  by  the 
action  of  living  organisms  has  been  termed 
"  bacteriolysis." 

The  quantity  of  sewage  per  head  of  the 
population  to  be  treated  daily  varies  consider- 
ably in  different  districts.  It  depends  upon 
the  water  supply,  the  nature  of  the  district, 
whether  residential  or  trading,  and  upon  the 
water-tightness  or  otherwise  of  the  sewers. 
About  30  to  40  gallons  per  head  per  day  is  a 
common  amount,  but  in  some  cases  the 
quantity  may  rise  tox50  or  60  gallons,  according 
to  local  circumstances. 

STANDARDS  OF  PURITY. — Before  proceeding 
to  consider  the  various  means  adopted  for 
purifying  sewage  it  will  be  well  to  refer  briefly 
to  the  question  of  the  standard  of  purity 
desired.  Although  no  fixed  standard  is,  or 
could  be,  advantageously  recognised  as  uni- 
versally applicable,  it  is  nevertheless  needful 
to  have  in  mind  a  safe  standard  for  average 
•conditions  as  a  guide  in  checking  the  results 
obtained  in  any  given  case.  Analytical  results 
are  sometimes  recorded  in  grains  per  gallon, 
and  sometimes  in  parts  per  100,000.  For 
purposes  of  comparison  by  conversion  it  should 
be  remembered  that  1  Ib.  avoirdupois  = 
7,000  grains,  and  1  gallon  of  water  =  70,000 
grains,  so  that  7  grains  per  gallon  =  10  parts 
per  100,000.  Thus  to  convert  grains  per 
gallon  to  parts  per  100,000  divide  by  7  and 
multiply  by  10,  or  conversely  to  convert  parts 
per  100.000  into  grains  per  gallon  multiply  by 
7  and  divide  by  10.  In  comparing  analyses 
of  sewage  effluents  with  the  crude  sewage  it  is 
important  to  remember  that  the  chlorine  figure 
serves  as  a  useful  guide  to  the  strength  of  the 
sewage,  and  that  no  process  of  purification  can 
remove  it,  so  that  the  amount  present  before 
and  after  purification  should  bear  close  com- 
parison. If  they  do  not  so  correspond  the 
effluent  will  have  been  obtained  from  a  weaker 
sewage,  thus  showing  an  apparently  greater 
percentage  of  purification  by  the  treatment 
.than  is  actually  the  case.  A  sewage  of  average 


strength  contains  from  10  to  12  parts  chlorine 
per  100,000,  but  this  depends  largely  upon 
the  quantity  in  the  water  supply  and  manu- 
facturing wastes  entering  the  sewers.  The 
chlorine  itself  is  not  important,  and  it  is  not 
necessary  that  it  should  be  removed,  but  the 
amount  present  should  be  ascertained  for  the 
above  reasons. 

Good  sewage  effluents  should  contain  not 
more  than  2  parts  per  100,000  of  organic 
matter  in  solution,  and  none  in  suspension ; 
the  albuminoid  ammonia  should  be  less  than 
'I  per  100,000  ('07  grain  '  per  gallon)  ;  the 
nitrogen  in  the  form  of  nitrates  (oxidised 
nitrogen)  should  exceed  '5  part  per  100,000 
('35  grain  per  gallon);  and  the  oxygen 
absorbed  at  80°  F.  in  4  hours  for  good 
effluents  should  be  less  than  1*0  part  per 
100,000  ('7  grain  per  gallon).  The  larger 
the  quantity  of  nitrates  present  the  more 
thoroughly  lias  the  sewage  been  oxidised,  and 
this  is,  therefore,  the  best  indication  of  the 
work  done  on  the  percolating  or  contact  beds 
in  the  last  stage  of  purification.  The  free 
ammonia  of  itself  is  harmless,  and  is  not  of 
great  importance.  A  simple  but  useful  rough 
test  of  purity  is  to  shake  a  half-filled  bottle  of 
the  effluent  vigorously  for  one  minute,  when 
all  frothing  should  disappear  in  three  seconds. 
Another  good  plan  is  to  keep  a  sample  of  the 
effluent  for  a  number  of  days  in  a  stoppered 
bottle  at  a  temperature  of  80°  F.,  under 
which  conditions  a  high-class  effluent  will  not 
give  off  any  offensive  smell.  Another  good 
plan  easily  adopted  is  to  keep  a  few  goldfish 
in  a  globe  or  aquarium  with  "effluent "  as  the 
only  water  supply.  This  should  be  changed 
daily,  and  if  the  fish  live  without  signs  of 
distress  it  proves  the  effluent  to  he  well 
aerated  with  sufficient  dissolved  oxygen  to 
enable  the  respiratory  processes  of  the  fish  to 
take  place  in  comfort. 

In  the  fifth  (1908)  report  of  the  Eoyal  Com- 
mission on  Sewage  Disposal  the  Commissioners 
state  that  "  an  effluent  can  best  be  judged  by 
ascertaining,  first,  the  amount  of  suspended 
solids  which  it  contains,  and  second,  the  rate 
at  which  the  effluent,  after  the  removal  of  the 


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suspended  solids,  takes  up  oxygen  from  water. 
In  applying  this  test  it  is  important  that  the 
suspended  solids  should  be  removed  and  esti- 
mated separately.  For  the  guidance  of  local 
authorities  we  may  provisionally  state  that  an 
effluent  would  generally  be  satisfactory  if  it 
complied  with  the  following  conditions  :— 

(1)  That   it   should   not   contain   more   than 
3  parts  per  100,000  of  suspended  matter ;  and 

(2)  that,  after  being  filtered    through  filter- 
paper,  it  should  not  absorb  more  than  : 

(«)  -5  part  by  weight  per  100,000  of  dissolved  or 
atmospheric  oxygen  in  24  hours. 

(6)  1-0  part  by  weight  per  100,000  of  dissolved  or 
atmospheric  oxygen  in  48  hours. 

(c)  1-5  part  by  weight  per  100,000  of  dissolved  or 
atmospheric  oxygen  in  5  days. 

METHODS  OF  PURIFICATION. — Turning  now 
to  the  principal  methods  in  use  for  the  purifi- 
cation of  sewage,  these  may  be  broadly 
classified  in  two  divisions,  viz.  :  (1)  Processes 
for  preliminary  clarification,  and  (2)  methods 
for  the  final  oxidation  of  the  impurities  con- 
tained in  the  clarified  liquid.  The  first  stage 
of  the  treatment  is  carried  out  by  means  of 
screening,  sedimentation,  precipitation,  either 
with  or  without  chemicals,  and  by  liquefying 
in  the  septic  tank.  The  second  stage,  or  oxi- 
dation process,  may  be  accomplished  by  land 
treatment,  either  in  the  form  of  broad  irriga- 
tion or  land  filtration,  and  by  contact  beds  or 
percolating  filters.  Other,  but  less  widely 
adopted,  means  of  disposal  are  the  dry-earth 
system,  as  in  Eastern  countries,  sea-disposal, 
evaporation,  and  electrolysis. 

SCREENING. — Coarse  screening  is  essential 
upon  arrival  of  the  sewage  at  the  works,  what- 
ever process  may  be  subsequently  followed. 
Its  object  is  to  remove  the  grosser  suspended 
matters  only,  such  as  paper,  rags,  orange-peel, 
sticks,  &c.  Various  classes  of  screens  are 
used,  including  hand-screens  in  small  works, 
automatically  cleansed  screens  of  a  variety  of 
design,  and  rotary  power-driven  screens  for 
the  larger  undertakings.  Fine  screens  choke 
readily,  and  the  cost  of  cleansing  is  usually 
too  great  to  justify  their  introduction. 

DETRITUS  AND  SEDIMENTATION  TANKS. — A 
detritus  or  grit  tank  is  generally  necessary 


for  the  purpose  of  intercepting  the  heavy 
mineral  matter  in  the  sewage,  such  as  grit, 
sand,  and  road  detritus,  especially  if  the  dis- 
trict is  a  hilly  one,  otherwise  this  material 
soon  accumulates  in  the  septic  or  sedimenta- 
tion tank  and  increases  the  labour  of  removal. 
A  detritus  tank  is  obviously  the  more  necessary 
where  a  town  is  sewered  on  the  "combined 
system,"  owing  to  the  greater  proportion  of 
grit  in  the  sewage.  The  velocity  through  a 
detritus  tank  should  be  sufficient  to  carry 
forward  the  suspended  organic  matter,  but 
just  slow  enough  to  allow  the  grit  to  settle  to 
the  bottom  of  the  tank  for  daily  removal. 
Two  shallow  tanks  (Fig.  1)  of  a  size  capable 


Irdei 


SECTION 
FlG.  1.— Detritus  Tank. 

of  giving  a  velocity  of  about  80  ft.  per  minute 
to  the  sewage  may  be  used  and  cleared  alter- 
nately. For  very  small  works,  where  regular 
labour  is  limited,  it  may  be  found  more  con- 
venient to  allow  all  the  solid  contents  of  the 
sewage  to  go  forward  to  the  sedimentation 
tank.  A  certain  proportion  of  grit  in  sludge 
is  found  to  assist  the  work  of  pressing  and 
drying  where  these  processes  are  carried  out. 
The  term  sedimentation  tank  is  used  more 
especially  in  connection  with  tanks  in  which 
sewage  is  allowed  to  settle  without  the  aid  of 
specially  added  precipitants,  whilst  the  expres- 
sion precipitation  tank  implies  the  use  of 
chemicals  or  other  precipitants  to  assist  the 
settlement.  Some  sewages  are  very  difficult 
to  settle,  such  as  those  containing  wool 
scouring  liquor,  tannery  and  brewery  wastes, 
and  to  obtain  a  good  tank  effluent  the  deposit 


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ENCYCLOPEDIA  OF 


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must  be  removed  after  every  first  or  second 
filling.  Fermenting  deposit  several  days  old 
gives  off  gas,  which  rises  and  carries  up  the 
suspended  matter  with  it,  and  thus  greatly 
deteriorates  the  quality  of  the  effluent.  Sedi- 
mentation tanks,  if  worked  so  as  to  keep  the 
sewage  contents  "  fresh,"  give  rise  to  little  or 
no  nuisance  from  smell.  (See  also  art  id1* 
"PRECIPITATING  OR  SETTLING  TANKS,"  "  IVES' 
TANK,"  "  DORTMUND  TANK,"  "  CANDY  SETTLING 
TANK,"  "ABSOLUTE-REST  TANK,"  "  DUNDRUM 
TANK,"  and  "  COSHAM  TANK.") 


but  it  had  no  considerable  practical  application 
until  proposed  for  the  city  with  which  Mr. 
Cameron  was  then  connected.  At  first  it  was 
put  forward  that  the  septic  tank  solved  the 
sludge  difficulty,  that  it  destroyed  the  patho- 
genic bacteria  in  the  sewage,  and  that  the 
tank-liquor  was  more  easily  oxidised  than  the 
effluent  from  an  ordinary  sedimentation  tank. 
These  claims,  however,  have  not  been  sub- 
stantiated by  the  test  of  longer  experience. 
It  is  well  known  that  all  the  organic  solids 
are  not  digested  by  the  septic  tank,  and  that 


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SEDIMENTATION 


SECTION  AT  AB 


FIG.  '2. — Preliminary  Preparatiou  Tank  (see  p.  403). 
SEPTIC    TANKS. — The  object   of    the   septic     the  amount  varies  according  to  the  character 


tank,  as  introduced  by  Mr.  Cameron,  City 
Surveyor  of  Exeter,  in  the  year  1895-6, 
was  "  to  bring  the  sewage  into  such  a  condi- 
tion by  arresting  the  solids  in  suspension  as 
to  make  the  filtration  on  artificial  filters 
practicable  ;  at  the  same  time  taking  advan- 
tage of  the  solvent  action  that  goes  on  in  the 
arrested  solids,  so  as  to  make  the  quantity  of 
deposit  or  sludge  as  small  as  possible."  This 
idea  of  digesting  solid  sewage  matter  by 
passing  it  through  a  sealed  tank  was  not  new, 


of  the  sewage.  At  Birmingham  the  suspended 
matter  digested  or  converted  into  gas  is  put 
at  only  10  %,  Leeds  30  %,  Manchester  25  %, 
Sheffield  about  33  %.  With  a  domestic  sewage 
of  average  strength  a  digestion  of  25  to  30% 
is  probably  the  maximum  likely  to  be  realised. 
Little  or  no  improvement  is  experienced  in 
the  bacterial  condition  of  the  septic  tank 
effluent  as  compared  with  the  crude  sewage, 
neither  is  such  effluent  found  to  be  more 
easily  oxidised  on  the  contact  or  percolating 


400 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


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bed  in  consequence  of  its  passage  through  the 
tank.  This  is  found  to  be  the  case  with 
ordinary  domestic  sewages,  and  also  with 
those  containing  "  trade  wastes,"  as  confirmed 
by  the  experience  of  Huddersfield,  Rochdale, 
Leeds,  and  other  places.  In  fact,  it  is  now 
generally  recognised  to  be  a  mistake  to  carry 
the  anaerobic  changes  too  far,  as  by  so  doing 
the  subsequent  nitrification  of  the  effluent  is 
suspended.  An  "  over-septicised  "  effluent  is 
usually  a  very  offensive  liquid,  owing  to  the 
increase  of  sulphuretted  hydrogen  produced, 
is  invariably  the  cause  of  much  trouble  and 
litigation  at  sewage  works  through  the  nuisance 
thus  set  up,  and  is  also  very  difficult  to 
subsequently  purify. 

The  quantity  of  solids  in  suspension  in  a 
septic  tank  effluent  varies  with  the  length 
of  time  the  tank  has  been  in  use  with- 
out cleansing,  but  the  proportion  increases 
seriously  as  time  goes  on,  so  that  the  quantity 
of  liquid  which  can  be  satisfactorily  oxidised 
on  the  aerobic  beds  decreases  in  proportion. 
On  the  average  there  may  be  from  15  to  20 
parts  solids  in  suspension  per  100,000,  but 
this  amount  may  be  doubled  after  6  months' 
working. 

With  regard  to  the  question  of  the  proper 
periods  for  cleansing  septic  tanks,  no  uniform 
rule  will  be  applicable,  but  the  observance  of 
the  proportion  of  solids  coming  off  in  the 
tank  liquor  from  time  to  time  must  be  the 
guide.  Should  this  percentage  become  too 
great  the  filters  will  suffer  and  the  effluent 
therefrom  deteriorate.  In  these  circumstances 
the  septic  tank  must  be  cleansed  and  the 
filters  allowed  time  to  recuperate.  If  a  tank 
has  been  allowed  to  work  for  a  long  period  of 
from  1  to  2  years,  it  is  commonly  found  that 
the  organic  sludge  has  become  fairly  well 
digested  and  settled  together  containing  from 
80  to  85%  of  moisture,  whereas  the  sludge 
from  a  tank  cleared  at  short  intervals  may 
contain  W%  more  water.  The  sludge,  upon 
removal  from  the  tank,  is  oftentimes  very 
offensive,  especially  where  there  is  brewery 
waste  in  the  sewage.  Where  it  is  desired  to 
keep  the  liquor  feeding  the  filters  as  uniform 


as  possible,  the  fresh  undigested  part  of  the 
sludge  at  the  bottom  of  a  tank  is  sometimes 
not  removed  when  clearing  is  undertaken, 
and  further,  if  tanks  are  in  duplicate,  as  they 
should  be,  a  clean  tank  may  be  filled  with 
septic  liquor  from  an  adjoining  tank  so  as  to 
hasten  the  full  development  of  septic  con- 
ditions in  the  newly  cleansed  tank.  The 
latter  method,  as  tested  at  Rochdale,  is  to  be 
preferred  to  allowing  sludge  to  remain  in  the 
tank  as  first  mentioned. 

One  leading  function  of  the  septic  tank  is 
the  equalisation  of  the  variations  in  strength 
of  the  sewage  delivered  to  the  works  and  the 
production  of  a  more  uniform  effluent  for  sub- 
sequent treatment.     Another  chief  object  is  to 
bring  about  as  large  a  settlement  of  digestion 
of  suspended  solids  as  possible,  and  upon  this 
directly  depends  the  choice  of  the  most  favour- 
able rate  of  flow  to  be   adopted.     It  is   not 
possible,  however,  to  lay  down  any  hard  and 
fast  rules  equally  applicable  to  all  cases  as  to 
the  length  of  time  the  sewage  should  be  sub- 
jected   to    anaerobic   conditions    in    passing 
through    the    septic    tank,    as  a    good   deal 
depends   on   the    nature,    temperature,    and 
strength  of  the  sewage  to  be  dealt  with.      Re- 
gard must  also  be  had  to  the  length  of  time 
and  distance  the  sewage  may  have  travelled  in 
the  outfall  sewer  before  arrival  at  the  site  of 
the  disposal  works.     In  the  case  of  a  long  out- 
fall having  little  fall,  septic  conditions  may  be 
well  advanced,  and  the  sewage  will  have  under- 
gone   a   thorough  mechanical   disintegration 
with  bacterial  decomposition  and  hydrolysis. 
Such  conditions  may  well  be  contrasted  with 
those   which  obtain  in  the   case  of   a  small 
works  serving  a  village,  mansion,  or   public 
institution,    where  the  septic   tank  would  be 
comparatively  small  and  the  sewage  reaches 
the   outfall   in  a  thoroughly  fresh   condition 
within  a  very  few  minutes  of  leaving  its  source. 
In  such  circumstances  the  tank  accommoda- 
tion needs  to  be  proportionately  larger  than 
that   required   for   a  large  town,    where   the 
greater   part  of  the  sewage  may  be   several 
hours  journeying  to  the  outfall. 

In  practice  it  would  appear  that  the  liquid 


M.S.E. 


401 


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receives  the  necessary  preparation  for  subse- 
quent purification  on  aerobic  beds  by  making 
the  septic  tank  of  such  a  size  as  will  admit  of 
the  sewage  sufficiently  approaching  a  state  of 


Tangential  Sewage  Inlet 


Sectional   Elevation. 


Tank  Effluent  Outlet  Pipe 


Plan. 


FIG.  3.— See  Candy  Settling  Tank  (p.  68). 

rest  to  allow  of  the  precipitation  of  nearly  the 
whole  of  the  solids,  and  also  by  constructing 
it  of  sufficient  depth  to  give  space  for  retain- 
ing the  same  until  the  putrescible  matter  has 
been  broken  down.  At  Exeter,  the  home  of 


the  septic  tank,  storage  approaching  2  days' 
flow  was  provided,  and  the  past  practice  of 
the  Local  Government  Board  was  to  stipulate, 
first,  for  1^  days'  dry  weather  flow,  later  for 
1^  days',  and  now  for  1  day's 
flow.  The  tendency  of  the  present 
time  is  in  the  direction  of  still 
further  reducing  the  period  of 
retention  in  the  septic  tank,  and 
a  storage,  in  duplicate,  for  one- 
half  day's  flow  is  doubtless  suffi- 
cient in  many  cases.  With 
Birmingham  sewage,  24  hours' 
septic  treatment  is  considered 
advantageous,  but  much  depends 
on  the  strength  of  the  sewage. 

In  this  connection  it  should  be 
stated  that  the  experience  of  many 
engineers  is  in  favour  of  dealing 
with  well  sedimented  sewage  upon 
bacteria  beds,  with  the  special 
object  of  avoiding  septic  conditions 
altogether,  and  of  completing  the 
purification  of  the  sewage  whilst 
it  is  as  "  fresh  "  as  possible,  thus 
contributing  largely  to  the  avoid- 
ance of  possible  nuisance  from 
smell.  In  the  case  of  many  classes 
of  sewage,  the  idea  of  the  septic 
tank  is  falling  into  disfavour  as 
experience  has  shown  that  it  is 
not  necessary,  and  indeed  is  some- 
times positively  harmful,  that 
sewage  should  be  made  putrid  (as 
the  name  implies)  preparatory  to 
the  second  or  oxidising  stage  of 
the  purification  process. 

Tanks  of   the   Dortmund   type 
(see    "  DORTMUND    TANKS")    have 
been    tried    for    the    preliminary 
preparation    of   the    sewage,    but 
trouble    commonly    arises    from 
the    deposits     of     sludge     and 
bacterial  growtbs  on  the  inner  walls,  which 
deposits,  as  they  decompose,  are  carried  away 
in    the    effluent.      If    kept    free    from   this 
obiection  this  type  of  tank  gives  better  settle- 
enters   and  leaves  the 


•e  Outlet 
Pipe 


ment   as  the  sewage 


402 


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MUNICIPAL   AND   SANITAKY  ENGINEERING. 


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tank  on  the  upward  flow  principle,  but  it 
is  not  probable  that  the  degree  of  digestion 
of  the  sludge  is  equal  to  that  which  takes 
place  in  the  ordinary  rectangular  form  of 
tank. 

Recent  experience  in  the  use  of  septic  tanks, 
both  open  and  closed,  goes  to  show  that,  unless 
there  is  some  special  local  reason  to  the  con- 
trary, no  real  advantage  is  gained,  either  as 
regards  the  digestion  of  sludge  or  quality  of 
the  tank  liquor,  by  constructing  a  closed  or 
practically  air-tight  tank.  The  roofing  over  of 
the  tank,  however,  has  the  effect  of  keeping 
the  gases  given  off  by  the  septic  sewage  under 
better  control,  so  as  to  limit  the  nuisance 
from  smell,  as  experienced  at  Gosport,  Car- 
shalton,  Guildford,  and  Ilford.  A  light  cover- 
ing, such  as  of  galvanised  iron,  is  sometimes 
useful,  as  it  prevents  disturbance  of  the 
surface  scum  by  wind  and  rain,  and  hides 
the  unsightly  appearance  of  a  septic  tank 
in  use. 

The  inlets  and  outlets  to  and  from  open  septic 
tanks  should,  of  course,  be  submerged  as  in 
the  case  of  the  covered  tank,  and  may  be 
arranged  by  passing  the  sewage  in  and  out  of 
the  tank  over  a  weir  behind  a  scum  board  to 
avoid  disturbance  of  the  general  body  of  the 
sewage  or  the  surface  of  the  scum. 

The  liquor  from  a  closed  tank  sprayed  upon 
filters  or  distributed  on  land  is  much  more 
likely  to  cause  nuisance  than  a  similar  effluent 
from  an  open  tank,  but  where  the  sewage  is 
prepared  in  plain  sedimentation  tanks  and 
passed  through  the  final  stage  of  purification 
whilst  fresh,  there  is  but  little  risk  of  nuisance 
under  proper  management  with  sewages  of 
average  quality.  "Contact  beds"  in  good 
working  order  are  less  likely  to  cause  nuisance 
from  smell  than  "  percolating  beds  "  on  which 
the  sewage  is  sprayed,  and,  from  the  nuisance 
point  of  view,  the  less  the  sewage  is  agitated 
the  better. 

The  gas  generated  in  closed  septic  tanks 
consists  of  about  73  °/0  marsh  gas  which  is 
inodorous,  6  %  of  carbon  dioxide,  5  %  hydro- 
gen, and  a  quantity  of  nitrogen.  It  burns 
freely,  and  has  been  estimated  to  possess  from 


one-half  to  two-thirds  the  value  of  coal  gas  of 
16  candle  power.  The  gas  is  not  luminous  of 
itself,  but  becomes  so  when  burnt  with  an 
incandescent  mantle.  Dangerous  explosions 
have  occurred  with  the  gas,  and  care  in 
handling  it  or  bringing  a  light  to  the  septic 
tank  should  be  exercised. 

The  liquor  from  a  septic  tank  often  shows  a 
marked  increase  in  the  total  solids  in  solution 
or  fine  suspension,  and  several  expedients 
have  been  tried  to  mechanically  strain  out  the 
latter.  Filtering  materials  of  varying  grade 
and  quality  have  been  placed  at  the  outlet  end 
of  the  tank  in  such  a  manner  that  the  liquor 
should  pass  through  and  be  subjected  to  rough 
filtration.  Experiments  of  this  sort  have  been 
tried  at  Leeds,  Guildford,  Chester,  and  Ilford, 
but  the  materials  rapidly  choke,  and  in  one 
way  or  another  become  ineffective.  At  Salford 
the  precipitation  tank  liquor  is  forced  through 
"  roughing  filters,"  under  a  head  of  5  ft.  6  in., 
and  by  this  means  75%  of  the  suspended 
matter  is  removed  before  passing  the  water  on 
to  the  percolating  beds.  The  roughing  filters 
are  3  ft.  deep  and  consist  of  coarse  gravel 
^  in.  to  1  \  in.  diameter.  The  liquor  is  passed 
through  at  the  high  rate  of  4,000  gallons  per 
square  yard  per  day. 

Before  passing  to  the  low-level  percolating 
filters  at  Friern  Barnet  the  precipitated 
sewage  is  given  2  hours'  treatment  in 
roughing  filters,  or  contact  beds  containing 
medium-sized  clinker,  and  by  this  means  a 
good  deal  of  the  suspended  matter  is  removed. 
At  Birmingham  "  Dortmund "  tanks  are 
placed  between  the  septic  tanks  and  the 
filters.  The  tank  liquor  contains  over  19  parts 
per  100,000  of  suspended  matter  and  about 
75%  of  this  is  removed  by  the  Dortmund 
tanks. 

For  average  domestic  sewages  which  have 
been  roughly  screened  and  subjected  to  simple 
sedimentation,  a  "  Preliminary  Preparation 
Tank"  of  the  design  shown  in  Fig.  2  (p.  400)  will 
be  found  advantageous  for  the  elimination  of  a 
large  proportion  of  the  suspended  solids.  At 
the  inlet  end  the  heavier  portion  of  the  solids 
still  remaining  in  the  sewage  is  held  back  in 


403 


D  D  2 


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ENCYCLOPEDIA  OF 


SEW 


a  compartment  containing  iron  baffle  plates, 
whilst  further  dissolution  and  subsidence  of 
fine  suspended  matter  takes  place  in  storage 
compartments  behind  submerged  cross  walls 
preparatory  to  an  aerobic  treatment  in  con- 
tact with  well  vitrified  clinker,  under  which 
latter  the  partially  clarified  sewage  enters  by 
means  of  an  aerating  floor  and  passes  upwards 
and  over  a  sill  to  the  adjoining  compartment 
or  away  to  the  tank  effluent  channel  off  which 
the  supplies  to  the  percolating  beds  are  taken. 
The  sludge,  or  deposit,  from  all  the  compart- 
ments of  this  tank  is  readily  removed  by 
opening  the  outlet  valves  provided  for  each 


PRELIMINARY  PREPARATION  OF  SEWAGE  BY 
CHEMICAL  PRECIPITATION. — At  one  time  chemi- 
cal precipitation  was  looked  upon  as  a  leading 
method  of  purification,  but,  as  a  result  of 
recent  developments  in  sewage  purification, 
it  must  now  be  regarded  as  an  auxiliary 
means  of  preliminary  preparation  of  certain 
classes  of  sewage,  mainly  those  containing 
"  trade  wastes,"  for  the  purpose  of  rendering 
the  same  suitable  for  subsequent  distribution 
upon  oxidising  beds.  The  chemical  precipi- 
tation of  domestic  sewage  with  a  2  hours'  rest 
may  produce  a  tank  liquor  containing  an 
average  of  2  or  8  parts  per  100,000  of  sus- 


Inlet 


Effluent 
Overflew 


pipe 


#?-,• /:&-•#/;>  ;- 


outlet 


SECTION  A  TO  B 

FIG.  4. — See  Precipitating  or  Settling  Tank  (p.  335). 


separate  chamber,  such  outlets  being  all  con- 
nected up  with  a  single  sludge  outlet  drain 
which  discharges  under  the  hydrostatic  head 
or  pressure  afforded  by  the  sewage  in  the  full 
tank,  thus  reducing  labour  to  a  minimum.  The 
effluent  from  the  tank  is  well  prepared  for 
passing  through  "  distributors  "  upon  aerobic 
trickling-filters  without  causing  trouble  from 
clogging,  or  it  may  with  advantage  be  satis- 
factorily dealt  with  direct  upon  land. 

Another  means  of  reducing  the  suspended 
solids  has  been  suggested  consisting  of  the 
addition  of  a  few  grains  of  lime  per  gallon  to 
the  septic  tank  liquor ;  this  also  has  the  effect 
of  reducing  the  offensive  character  of  the 
liquor. 


pended  matter  as  compared  with,  say,  4  or  5 
parts  per  100,000  in  the  case  of  a  continuous 
flow  tank  working  at  an  8-hour  rate.  Of  the 
many  precipitants  employed  in  different  places, 
lime  and  alumino-ferric  are  very  largely  used 
either  alone  or  together,  according  to  the 
nature  of  the  sewage.  When  used  together 
some  4  or  5  grains  per  gallon  of  lime  are 
mixed  with  the  sewage  as  compared  with 
from  2  to  4  grains  of  alumino-ferric,  but  the 
best  proportions  to  be  adopted  necessarily 
vary  with  the  nature  of  the  sewage,  and  are 
dictated  by  experience.  These  precipitants 
are  used  at  Baling,  Willesden,  Dorking,  York, 
Friern  Barnet,  and  other  places.  Lime  is  also 
used  in  conjunction  with  copperas  (ferrous 


404 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


SEW 


sulphate),  and  at  Kingston  alumino-ferric  is 
used  with  blood,  charcoal,  and  clay  (A.  B.  C. 
process).  Other  precipitants  are  Hanson's 
sulphurous  powder,  ferric  sulphate,  aluminum 
sulphate,  ferrozone,  and  sulphuric  acid, 
between  4  and  5  grains  of  the  latter  being 
used  at  Rochdale,  where  the  sewage  is  strong, 
with  about  7  grains  of  alumino-ferric.  The 
average  cost  of  precipitant  in  five  towns  where 
about  6  grains  per  gallon  of  alumino-ferric 
alone  is  used  is  about  15s.  per  million  gallons 
of  average  daily  flow,  as  compared  with 
lls.  per  million  gallons  in  five  other  towns 
using  5  grains  of  lime  and  3  grains  alumino- 
ferric  on  the  average.  From  80  to  85  %  of 
the  suspended  matter  in  the  crude  sewage  is 
precipitated  by  the  use  of  from  6  to  7  grains 
per  gallon  of  alumino-ferric,  but  it  should  be 
remembered  that  the  greater  the  amount  of 
suspended  solids  in  the  crude  sewage  the 
easier  it  is  to  secure  a  good  percentage  of 
reduction.  At  Kingston,  above  referred  to, 
no  less  than  95  °/0  of  suspended  matter  is 
thrown  down,  showing  the  A.  B.  C.  method 
to  be  an  efficient  means  of  precipitation,  but 
the  quantity  of  sludge  produced  is  large. 
The  lime  process  does  not  yield  a  very  satis- 
factory effluent,  but  is  useful  to  neutralise  an 
acid  sewage.  There  is  considerable  difficulty 
in  accurately  adjusting  the  quantity  of  lime 
to  the  sewage,  usually  resulting  in  much  lime 
being  left  in  solution  (see  "  LIME  PROCESS  "). 
The  proper  precipitant  to  use  in  any  individual 
case  depends  upon  the  chemical  composition 
of  the  sewage;  special  sewages  require  special 
treatment — for  example,  at  Bradford  and 
Rochdale  sulphuric  acid  is  used  to  neutralise 
the  alkali  in  the  wool-scouring  refuse,  whilst 
large  quantities  of  lime  are  added  to  the 
Burton  -  on  -  Trent  sewage  on  account  of 
the  large  proportion  of  brewery  waste  it 
contains. 

The  most  effective  method  of  adding  chemi- 
cal precipitants  is  in  the  form  of  a  solution 
and  well  agitating  the  sewage  by  mechanical 
means.  At  small  works  precipitants  such  as 
ferrozone  and  alumino-ferric  is  often  added  in 
the  form  of  a  solid  block  placed  in  the  main 


sewage  carrier  and  allowed  to  dissolve  by  the 
flow  of  sewage. 

The  clarification  of  sewage  in  tanks  with 
the  aid  of  chemical  precipitants  may  be 
expected  to  cost  about  ,£3  per  million  gallons 
of  dry  weather  flow  of  sewage,  including  labour, 
chemicals,  and  loan  charges,  as  against  about 
one-half  that  amount  for  simple  continuous 
flow  settlement  or  in  open  septic  tanks.  But 
in  this  connection  it  must  be  remembered 
that  chemically  precipitated  sewage  contains 
less  suspended  and  colloidal  matter  than 
sewage  which  has  been  settled  without 
chemicals  or  through  a  septic  tank,  so  that  a 
larger  quantity  can  be  treated  per  cubic  yard 
capacity  of  oxidising  filters  and  a  finer  grade 
of  material  may  be  used. 

Septic  tank  liquors  frequently  contain  more 
colloidal  matter  than  their  corresponding 
sewages,  the  effect  of  which  is  to  increase  the 
clogging  effect  upon  fine-grained  filters.  For 
very  strong  sewages,  therefore,  a  preliminary 
preparation  by  chemical  precipitation  may  be 
more  advantageous  than  by  septic  tank  treat- 
ment, especially  in  cases  where  the  sewage 
contains  tannery  or  brewery  wastes.  A  large 
part  of  the  colloidal  matters  are  thrown  down 
as  sludge  by  chemical  precipitation,  and 
sludge  so  produced  is  commonly  less  costly 
per  ton  to  press  than  that  from  septic  tanks, 
but  the  volume  produced  is  larger. 

Suitable  preliminary  treatment  of  any 
sewage  must  be  regarded  as  a  most  important 
part  of  the  process  of  purification,  as  upon 
this  largely  depends  the  degree  of  success,  or 
otherwise,  of  the  second  or  oxidising  stage  to 
which  the  tank  liquor  is  subjected,  and  the 
most  economical  and  advantageous  local 
means  of  dealing  with  the  sludge  will  doubt- 
less always  prove  a  leading  factor  in  the 
choice  of  a  system  of  sewage  disposal. 

Having  dealt  in  the  preceding  pages  with 
the  various  methods  of  "  preliminary  prepara- 
tion "  of  sewage  and  with  the  question  of  the 
disposal  of  sludge  resulting  from  such  treat- 
ment, the  remaining  problem  to  be  considered 
is  principally  that  of  the  various  methods 
of  thoroughly  oxidising  the  organic  matters 


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contained,  in  solution  and  in  suspension,  in 
the  partially  clarified  effluents  from  the  pre- 
liminary preparation  tanks.  This  second 
stage  of  the  process  is  carried  out  upon  arti- 
ficially prepared  sewage  filters  or  upon  land. 
Filters,  as  now  constructed,  are  broadly 
speaking  of  two  classes,  viz. :  "contact  beds" 
and  "percolating  filters." 

CONTACT  BEDS. — These  are  simply  tanks 
filled  with  some  durable  form  of  filtering 
material,  in  which  the  sewage  is  held  up  for 
a  definite  period  of  time  in  "  contact  "  with 
the  medium,  after  which  it  is  quickly  dis- 
charged and  the  bed  allowed  to  stand  empty 
for  a  fixed  period  in  order  that  it  may  aerate 
and  recuperate  in  readiness  for  the  next 
filling.  By  this  method  there  is,  therefore,  a 
continual  succession  of  periods  of  "  contact," 
or  work  alternating  with  periods  of  "  rest "  or 
recuperation.  With  percolating  filters  the 
sewage  is  permitted  to  regularly  percolate 
through  the  bed,  and  is  not  held  up  as  in 
the  preceding  case.  Both  types  of  filter  are 
capable  of  oxidising  organic  matter  in  solution 
in  sewage  when  working  under  proper  condi- 
tions, but  the  relative  merits  of  each  require 
careful  consideration  before  adoption  in  any 
particular  case.  Generally  speaking  at  the 
present  time  the  "percolation  bed  "  is  in  the 
greatest  favour,  and  is  capable  of  treating 
nearly  double  the  quantity  of  tank  liquor  per 
cubic  yard  of  medium,  as  compared  with  the 
contact  bed.  Exactly  what  takes  place  in  the 
course  of  purification  within  the  contact  bed 
is  not  fully  understood,  and  comparatively 
little  is  known  as  to  the  kinds  of  bacteria 
essential  to  purification,  but  it  is  generally 
believed  that  bacteriological  activity  during 
the  resting  or  aerating  period  of  the  bed  is 
an  important  and  indispensable  part  of  the 
cycle  of  work.  Some  purification  is  also 
doubtless  effected  by  worms,  infusoria  of 
many  kinds,  and  other  low  forms  of  life  in 
addition  to  bacteria. 

Contact  beds  in  several  instances  were 
first  constructed  by  simply  excavating  for  the 
bed  and  refilling  with  burnt  ballast  or  other 
conveniently  accessible  material  as  a  medium, 


but  there  are  many  objections  to  this  plan. 
Such  beds  can  seldom  either  be  made  or  kept 
water-tight,  as  rats  and  moles  burrow  through 
the  sides  and  bottom,  and  unpurified  sewage 
leaks  from  one  bed  to  the  other  and  finds 
underground  courses  and  outlets.  Trouble 
of  this  description  has  been  experienced  at 
Sutton,  Oswestry,  Heywood,  and  Halton, 
whilst  on  the  other  hand  somewhat  more 
satisfactory  results  have  been  experienced 
from  a  similar  mode  of  construction  in  heavy 
clay  soils  at  Burnley  and  Oldham.  The 
materials  within  contact  beds  should  be  of  a 
permanent  character,  not  easily  pulverised  or 
reducible  by  sinkage  or  crushing,  or  the  beds 
rapidly  lose  capacity  and  choke,  owing  largely 
to  insufficient  aeration  through  the  body  of 
the  bed  for  the  proper  development  of 
bacterial  life. 

In  the  construction  of  the  biological  contact 
bed  the  object  is  to  deal  with  a  foul  liquid 
containing  but  little  free  oxygen  and  large 
quantities  of  oxidisable  organic  matter,  the 
oxidation  of  which  is  effected  through  the 
agency  of  living  organisms  requiring  an 
adequate  supply  of  air.  The  growth  of  such 
organisms  coats  the  filtering  medium  with  a 
slimy  jelly  consisting  of  masses  of  bacteria 
and  zoogkea.  Dr.  Fowler  has  pointed  out 
that  if  this  material  is  placed  in  a  tube  con- 
taining air  and  connected  with  a  manometer 
(see  "MANOMETEK")  the  jelly  will  rapidly 
absorb  all  the  oxygen  and  produce  carbon 
dioxide.  This  action  will  sometimes  produce 
a  vacuum  of  several  inches  of  mercury, 
showing  that  there  is  little  need  to  force  air 
into  a  bed,  as  has  been  experimentally  tried, 
as  the  natural  interchange  of  gases  thus 
taking  place  is  sufficient  for  adequate  aeration. 

The  new  contact  bed,  of  course,  contains  no 
such  organisms,  but  the  sewage  itself  carries 
the  necessary  bacterial  life  for  its  purification, 
and  as  this  develops,  the  bed  is  gradually 
brought  into  a  state  of  high  efficiency,  as 
shown  by  the  presence  in  the  effluent  of 
increasing  proportions  of  nitric  acid.  After 
a  sufficient  contact  the  emptying  of  the  bed 
from  below  has  the  effect  of  drawing  a 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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further  supply  of  air  into  the  interstices 
of  the  material  at  each  period  of  rest.  The 
"  resting "  of  the  bed,  say  for  12  hours  out 
of  each  24,  is  one  of  the  distinguishing 
features  of  the  mode  of  working  a  bacterial 
bed  as  compared  with  the  earlier  sewage  and 
waterworks  filters,  the  action  of  which  was 
formerly  regarded  as  wholly  mechanical.  If 
the  bed  be  worked  at  a  high  speed  without 
sufficient  daily  rest  the  effluent  may  remain 
good,  but  the  capacity  of  the  bed  will  be 
reduced  by  the  rapidly  increasing  bacterial 
growths,  which  cause  the  bed  to  become  too 
spongy  and  prevent  its  liquid  contents  from 
draining  away.  Thus,  a  decrease  of  capacity 
is  accompanied  by  an  increase  in  efficiency, 
just  as  is  also  experienced  in  the  use  of  a 
waterworks  sand  filter  as  the  gelatinous 
growths  develop  on  the  surface  of  the  sand. 
If,  however,  the  growths  within  the  contact 
bed  become  so  great  as  to  interfere  with  the 
practical  utility  of  the  bed,  these  will  be 
rapidly  consumed  by  giving  the  bed  a  long 
rest  of  from  1  to  2  weeks,  at  the  end  of 
which  its  capacity  will  be  greatly  increased. 
A  longer  period  of  rest  than  this  is  not  advis- 
able, as  the  slimy  growth  or  bacterial  jelly 
coated  upon  the  material  of  the  bed  tends  to 
dry  up  and  so  to  inhibit  the  activity  of  the 
micro-organisms.  In  winter,  too,  their  action 
is  diminished  when  deprived  of  the  heat  of  the 
sewage  during  prolonged  periods  of  rest. 
When  once  a  bed  is  matured  it  is  better, 
therefore,  to  relieve  the  work  upon  it  by 
reducing  the  number  of  fillings  per  day  than 
to  put  it  out  of  use  altogether  when  not 
required  for  the  volume  of  sewage  to  be  dealt 
with. 

The  period  of  "contact"  in  a  bed  obviously 
has  an  important  bearing  on  the  area  of  beds 
required  for  any  given  volume.  The  ordinary 
8-hour  cycle  of  operations  allows  1  hour  to 
fill,  2  hours  resting  full  in  contact,  1 
hour  to  empty,  and  4  hours  resting  empty 
for  aeration.  Experience  shows,  however, 
that,  although  this  round  of  operations  may 
be  regarded  as  a  fairly  average  condition  of 
working,  it  admits  of  considerable  modifica- 


tion in  individual  circumstances.  The  age  of 
the  beds  and  the  strength  of  the  sewage 
treated  are  important  factors  of  the  case. 
The  present  tendency  is  to  shorten  the  period 
of  contact,  and  it  appears  clear  that  the  period 
of  rest  is  of  greater  importance  than  that  of 
contact.  The  bed,  too,  should  be  filled  and 
emptied  as  quickly  as  possible  so  that  all  parts 
from  top  to  bottom  may  be  uniformly  aerated 
throughout,  care  being  taken,  of  course,  that 
no  disturbance  of  the  materials  in  the  bed 
should  occur.  On  the  whole  about  half  an 
hour  for  filling,  1  hour's  contact,  with  half  an 
hour  or  a  little  more  for  emptying,  may  be 
taken  as  a  satisfactory  cycle,  subject  of  course 
to  modifications  to  suit  special  sewages  under 
treatment.  Assuming  a  maximum  of  6  hours' 
rest  this  will  allow  three  fillings  a  day,  or 
if  a  maximum  of  4  hours'  rest  only,  four 
fillings  in  the  24  hours. 

The  length  of  time  required  for  a  new  bed 
to  mature  varies  greatly  and  is  found  to  depend 
on  the  nature  and  strength  of  the  sewage 
and  on  the  temperature  prevailing  or  seasons 
of  the  year.  In  some  cases  it  has  been  barely 
more  than  a  matter  of  days,  in  others  it  has 
taken  about  three  weeks,  whilst  in  some  in- 
stances as  many  months  may  be  occupied  in 
the  development  of  the  necessary  growths. 
Provided  adequate  precautions  are  taken,  as 
by  the  use  of  detritus  chambers,  to  exclude 
inorganic  substances  such  as  road  grit,  &c., 
a  bacteria  bed  when  once  started,  if  intelli- 
gently worked,  should  continue  to  improve 
and  deal  with  increasing  quantities  of  sewage 
after  the  initial  reduction  of  liquid  capacity 
inseparable  from  a  new  bed  has  been  passed. 

The  question  of  the  permanent  liquid 
capacity  of  contact  beds  is  one  of  considerable 
importance  as  affecting  the  practical  working 
of  the  system  as  well  as  the  initial  outlay  in 
area  of  beds  and  subsequent  working  expenses 
in  renewal  of  the  material.  The  first  ex- 
periences of  loss  of  capacity  proved  to  be  very 
largely  due  to  the  use  of  unsuitable  and 
improperly  graded  materials  and  to  the  lack 
of  appreciation  of  the  distinction  between  loss 
which  occurs  whilst  the  bed  is  getting  into 


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condition  and  that  which  can  be  regarded  as  a 
genuine   "sludging   up"    of    its    interstices. 
Later  experience  shows  that  a  regular  working 
capacity     of     about     83  °/0     of     the     cubic 
contents  of  the  bed  can  be  relied  upon  in  the 
case  of  "  primary  contact  "  beds — a  proportion 
which  has  been  adopted  by  the  Local  Govern- 
ment Board  as  a  requirement  in  the  design  of 
new    schemes.     The   average    capacity   of    a 
"  secondary "  bed   receiving    effluent    from  a 
corresponding   primary  bed    is    about    40  % 
of     the     original     contents    of      the     empty 
tank.     Upon  the  first  filling  of  a  new  bed  its 
liquid    capacity    may    be    well    over     50  °/0 
of  the  total  cubic  contents,  but  this  proportion 
will  gradually  decline  as  the  bed  comes  into 
working   condition,    and    periodic   resting    is 
always  necessary  to  keep  the  bacterial  growths 
within  proper  limits.     A  marked  increase  of 
capacity  is  noticeable  after  the  bed  has  rested 
for    several    days    owing    to   more   complete 
drainage  and  to  the  removal  by  oxidation  of 
much    of    the    organic   matter    accumulated 
within    the    bed.     There    are    many   causes 
which  contribute  to   the  loss  of  capacity  in 
contact  beds,  some  of  which  may  be  avoided 
whilst  others  cannot.     Such  loss  is  due  princi- 
pally to  the  disintegration  and  consolidation 
of   the  material  within   the  bed,  insufficient 
drainage  and  aeration,  the  excessive  growth  of 
the  bacterial  jelly  and  other  low  forms  of  life 
due  largely  to  overwork  and  want  of  aeration, 
to  the  excessive  volume  of  tank  liquor  passed 
on  to  the  bed  and  the  relatively  large  amount 
of  suspended  matter  contained  in  such  liquid, 
and    to   the    deposition   of   colloidal   matters 
tending  to  choke  the   pores  of   the  filtering 
material.     Insoluble  matters  may  be  largely 
retained  on  the  surface  of  the  bed  by  using  a 
layer  of  finer  material  on  the  top,  the  upper 
portion  of   which  may  be  skimmed  off  from 
time  to  time  as  necessary,   and  the  surface 
periodically  loosened  by  means  of  a  fork. 

Some  latitude  is  permissible  in  regard  to 
the  depth  to  which  contact  beds  should  be 
constructed,  but  from  past  experience  it 
appears  that  a  depth  of  from  4  ft.  to  5  ft.  is  the 
most  generally  suitable.  A  depth  of  6  ft.  may 


be  regarded  as  a  maximum,  and  2  ft.  6  in.  as 
a  minimum.  A  good  deal,  however,  will 
depend  on  the  fall  available  in  any  given 
case  and  the  relative  cost  and  areas 
required  for  shallow  and  deep  beds  re- 
spectively. Generally  speaking,  the  depth 
of  a  bed  makes  little  or  no  difference  in  its 
efficiency  per  cubic  yard  of  filtering  material, 
but  at  Exeter,  it  is  interesting  to  note,  nitrifi- 
cation was  found  to  be  most  active  in  the 
body  of  the  filter  rather  than  at  the  top  or 
bottom,  and  the  greatest  purification  took 
place  at  the  depth  of  8  ft.  down. 

MATERIALS  FOR  CONTACT  BEDS. — In  selecting 
and  placing  materials  in  the  contact  bed  it 
must  be   remembered   that   the  object  is  to 
expose  a  maximum  surface  alternately  to  the 
sewage  and  to  the  air,  so  that  there  may  be 
ample  areas  over  which  the  bacterial  growths 
may  take  place,  and  with  which   the  sewage 
and   air   alternately    may  come    in    contact. 
The  material  should  be  hard  and  tough  and 
admit  of  the  sewage  and  air  alternately  filling 
all  its  interstices.     It  should  be  strong  enough 
to    resist   crushing   through    superincumbent 
weight.     If  the  material  is  too  much  honey- 
combed and  in  large  pieces,  there  may  be  a 
tendency  to  retain  stale  sewage  in  its  crevices, 
and  to  reduce  the  capacity  of  the  bed  by  hold- 
ing back  a  large  amount  of  liquid  by  capillary 
attraction.      The    material    should    be    well 
screened  free  from  dust  and  fine  stuff,  but  it  is 
not  necessary  to  keep  a  strictly  uniform  size 
or  grade  throughout  the  body  of  the  bed.     A 
variation  in  size  from  1  in.  to  3  in.  will  effect 
considerable  saving  in  the  expense  of  filling 
the  bed  which  would  otherwise  be  entailed  by 
two  great  a  refinement  in  the  grading.     The 
drains  or  aerating  tiles  on  the  floor  of  the  bed 
should  be  covered  with  larger- sized  material, 
and  the  top  of  the  bed  overlaid  with  a  6  in. 
layer  of  finer  grade,  with  the  object  of  keeping 
as  much  as  possible  of  the  suspended  matter 
in  the  sewage  upon  the  surface  of  the  bed. 
There  is  no  necessity  of  forming  the  bed  in 
layers  of  different-sized  materials  ;  uniformity 
throughout  gives  the  best  results. 

The  actual  material  selected  in  any  given 


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case  will  naturally  depend  very  largely  upon 
local  conditions  and  facilities  for  obtaining  a 
suitable  medium  at  the  lowest  cost.  Amongst 
those  which  have  been  successfully  employed 
are  good  hard  vitreous  clinker,  broken  brick 
rubble,  granite,  flints,  broken  "  saggers  "  from 
the  potteries,  hard  coal,  and  coke.  Slags  from 
iron  works  can  only  be  used  with  great 
caution,  as  they  may  be  liable  to  disintegrate 
under  the  action  of  septic  sewage,  but  the 
vitreous  slags  from  cold  blast  furnaces  have 
often  been  found  suitable.  Carbonate  of  lime 
is  soluble  in  the  effluent  from  septic  tanks,  and 
any  material  into  which  this  enters  largely 
will  be  liable  to  disintegration.  The  material 
used,  therefore,  should  not  effervesce  under 
hydrochloric  acid ;  it  should  be  clean  when 
put  into  the  beds,  and  be  washed  if  necessary. 
Refuse  destructor  clinker  is  often  used  where 
this  material  is  produced  at  or  near  the  site  of 
the  bacteria  beds,  but  only  the  harder  and  more 
vitrified  portions  should  be  employed.  All 
fine  friable  dust  and  small  material  should  be 
rejected. 

GRADE  OF  MATERIAL. — The  decision  as  to 
the  grade  of  material  to  be  used  should  depend 
largely  upon  the  amount  of  suspended  matter 
in  the  tank  liquor  to  be  treated,  but  there  is 
no  advantage  in  using  material  much  over 
3  in.  grade.  Large  material  does  not  neces- 
sarily prevent,  but  defers,  choking.  By  its 
use  a  considerable  part  of  the  sewage  is  not 
brought  sufficiently  into  contact  with  the 
surfaces  carrying  bacterial  growths  to  insure 
the  requisite  purification,  owing  to  the  large 
interstices  between  the  material.  With  a  well 
precipitated  tank  liquor  where  a  good  hard 
well  vitrified  clinker  is  used,  the  gauge  may  be 
from  1^  in.  to  |  in.  for  primary. beds,  and  f  in. 
to  ^  in.  for  secondary  beds — a  layer  of  coarse 
material,  2  in.  to  3  in.  gauge,  being  placed 
over  the  aerating  floor  tiles  to  assist  drainage 
and  ventilation  of  the  bed.  Coke  is  not  so 
good  a  medium  as  good  hard  clinker,  as  it  is 
apt  to  disintegrate  and  sometimes  to  float  in 
the  liquid.  The  "  saggers  "  from  the  potteries 
should  make  very  good  material,  and  in  that 
locality  can  be  delivered  in  the  rough  state  for 


about  2s.  per  ton,  or,  including  crushing, 
screening,  and  placing  in  the  beds,  between 
4s.  and  5s.  per  cubic  yard.  The  weight  of  a 
cubic  yard  is  about  18  cwts. 

DISTRIBUTION  OVER  CONTACT  BEDS. — For  the 
distribution  of  sewage  over  contact  beds,  the 
elaborate  troughing  of  iron,  zinc,  wood,  &c., 
complicated  with  notchings,  holes,  and  adjust- 
ing screws,  has  now  mostly  been  abandoned, 
and  simpler  methods  followed.  It  may  be 
accepted  that  every  detail  of  construction  con- 
nected with  works  for  the  purification  of 
sewage  should  be  of  the  simplest  possible 
description  so  as  to  work  with  the  minimum 
of  attention,  to  avoid  choking  by  suspended 
matters  in  the  sewage,  and  generally  getting 
out  of  order.  In  the  case  of  the  Manchester 
contact  beds,  the  sewage  is  admitted  from  the 
supply  channel  into  a  shallow  basin  within  the 
bed,  and  then  passes  over  a  semi-circular 
weir  on  to  the  material  of  the  bed,  in  which 
is  formed  a  series  of  radiating  channels  or 
grips,  into  which  is  placed  "finer  grade  material 
to  keep  the  grosser  solids  at  the  surface,  and 
as  the  porous  surface  of  these  channels  becomes 
choked,  the  sewage  is  gradually  carried  further 
forward  before  passing  down  into  the  bed. 
The  channels  are  turned  over  from  time  to 
lime  as  necessary  to  vary  their  position.  This 
method  has  the  important  advantage  of  being 
exceedingly  simple.  In  lieu  of  the  simple 
grips,  half-pipe  stoneware  channels  are  some- 
times used,  but  possess  no  real  advantages 
over  the  first-named  method,  except,  perhaps, 
the  placing  of  a  few  lengths  to  lead  off  from 
the  outlet  of  the  feed-siphon  valve.  In  either 
case  the  surface  of  the  beds  may  be  practically 
at  the  same  level  as  that  of  the  sewage  in  the 
septic  tanks,  unless  fall  is  required  for 
aeration,  for  long  storage  channels,  a  dosing 
tank,  or  for  other  reasons. 

For  a  full  bacterial  treatment,  and  a  good 
non-putrefactive  effluent,  double  contact  is 
necessary  for  most  sewages.  That  is  to  say, 
an  upper  or  first  contact  for  the  retention 
and  digestion  of  the  grosser  impurities  in  the 
tank  effluent  must  be  followed  by  lower  or 
second  contact  beds.  These  are  respectively 


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described  as  "  coarse "  and  "  fine "  beds, 
according  to  the  grade  of  material  used,  and 
as  a  rough  approximation  it  may  be  taken 
that  the  first  contact  will  remove  about 
50%  of  the  dissolved  impurity,  and  that 
the  second  contact  disposes  of  some  50% 
of  the  impurity  still  remaining  in  the 
effluent.  If  single  contact  only  is  given  the 
effluent  will  require  further  treatment  on  good 
pasture  land  as  in  the  case  of  the  Beaumont 
Leys  Farm  at  Leicester.  In  some  cases  a 
good  non-putrefactive  effluent  may  be  got  by 
subjecting  one-half  of  the  sewage  to  double 
contact  and  the  remainder  to  single  contact 
only,  and  then  mixing  the  effluents  so  obtained, 
thus  securing  what  may  be  regarded  as  one- 
and-a-half  contact.  The  "  secondary  "  beds 
in  such  a  case  would  be  made  proportionately 
smaller  and  pass  the  sewage  at  a  more  rapid 
rate,  but  this  reduction  in  area  is  not  recognised 
by  the  rules  of  the  Local  Government  Board. 

Automatic  gear  for  charging  and  emptying 
contact  beds  is  useful  in  small  works,  where 
labour  is  limited,  but  cannot  be  left  long 
unattended,  and  an  inspection  at  least  once  a 
day  is  needed.  All  apparatus  of  the  kind, 
however  well  made,  is  liable  to  get  out  of  order 
and  so  completely  derange  the  working  of  the 
purification  system  ;  neither  can  such  devices 
adapt  themselves  to  the  variations  of  strength 
and  flow  of  the  sewage.  A  bacterial  system 
must  be  worked  with  intelligence  and  variation 
of  control  according  to  the  fluctuations  of 
temperature  and  quantity  and  strength  of  liquid 
to  be  treated.  Manual  labour  alone  can  watch 
these  variations,  and  so  learn  by  experience 
how  to  secure  the  most  favourable  result. 
On  large  works,  where  labour  is  always  avail- 
able, manual  control  is  undoubtedly  the  best. 

A  very  large  variety  of  apparatus  has  been 
introduced  for  feeding  and  emptying  bacteria 
beds  and  for  various  other  purposes,  full 
details  of  which  will  be  found  in  the  catalogues 
of  the  principal  makers. 

The  length  of  time  a  contact  bed  can  be 
worked  before  it  becomes  necessary  to  take 
out  the  materials,  wash,  screen,  or  renew  the 
same,  depends  on  the  nature  and  grade  of  such 


materials,  the  amount  of  suspended  matter  in 
the  tank  liquor  treated,  and  other  factors. 
Such  "washing"  may,  however,  be  neces- 
sary every  4  or  5  years  in  primary  beds  and 
every  8  or  10  years  in  secondary  beds,  but 
the  true  period  in  any  given  case  depends 
entirely  upon  the  conditions  under  which  the 
beds  are  worked.  In  some  instances  it  may  be 
cheaper  to  renew  the  material  entirely  if  a  new 
supply  is  readily  obtainable,  but  more  often  it 
proves  economical  to  "  wash  "  the  old  material 
and  make  up  with  new.  The  cost  of  removing 
from  beds,  wheeling,  screening,  washing  by 
machinery,  and  replacing  and  making  up  loss 
with  new  material  commonly  varies  from  Is. 
to  about  2s.  3d.  per  cubic  yard,  as  compared 
with  similar  work  with  hand  washing  costing 
from  Is.  6d.  to  2s.  Id.  per  cubic  yard. 

The  deposition  of  colloidal  matter  greatly 
reduces  the  capacity  of  filters  in  some  cases, 
and  the  best  means  of  dealing  with  this 
difficulty  is  one  of  considerable  importance, 
but  has  not  hitherto  been  fully  investigated, 
though  increased  attention  has  been  directed 
to  the  subject  of  recent  years. 

PERCOLATING  BEDS  for  the  final  oxidation  of 
sewage  liquor  from  septic  or  precipitation 
tanks  are  of  more  recent  development  than 
contact  beds,  and,  at  present,  appear  to  be 
growing  in  favour.  The  essential  features  of 
the  percolating  system  as  distinguished  from 
treatment  by  "contact"  are  that  the  liquid 
is  not  held  up  in  a  water-tight  chamber  in 
stationary  contact  with  the  clinker  or  other 
medium  used,  but  is  applied  to  the  bed  so  as  to 
gradually  percolate  or  trickle  through,  passing 
en  route  over  the  surfaces  of  the  medium  which 
rapidly  become  coated  with  bacterial  growths. 
These  latter  act  upon  the  sewage  and  bring 
about  its  oxidation.  The  percolating  bed  is 
usually  made  deeper  than  the  contact  bed,  and 
special  means  should  be  taken  to  insure 
regular  and  thorough  aeration  of  the  whole  of 
the  filtering  medium  by  means  of  a  hollow  or 
aerating  floor  with  perforated  side  walls.  The 
percolating  bed  works  continuously,  with  the 
exception  of  short  regular  intervals  for  aeration, 
and  it  is  capable  of  treating  nearly  double  the 


410 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


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quantity  of  sewage  per  cubic  yard  of  bed 
capacity  as  compared  with  the  "  contact " 
system.  The  sewage  is  sprinkled,  in  a  more 
or  less  rain-like  fashion,  by  means  of  "  distri- 
butors" (see  "DISTRIBUTORS,  FOR  SEWAGE  "),  and 
an  important  point  is  to  secure  uniformity  of 
distribution  and  a  regulation  of  the  quantity 
passing  on  to  the  bed.  The  percolating  bed 
effluent  will  be  found  to  contain  more  suspended 
matter  than  that  from  the  contact  filter  and 
some  means  will  generally  be  needed  to  remove 
the  larger  portion  of  this.  Its  removal  from 
the  body  of  the  filter  in  this  way  is  advantage- 
ous, as,  in  the  case  of  the  contact  system,  it 
accumulates  within  the  bed  and  in  time 
chokes  the  pores  of  the  medium,  which  must 
then  be  removed  and  washed. 

The  depth  of  percolating  beds  may  usefully 
range  from  3  ft.  to  5  ft.  in  the  case  of  fine  grade 
materials,  and  from  5  ft.  to  10  ft.  with  medium 
or  course  grade  material.     The  extent  of  the 
purification  depends  largely  upon  the  length 
of  time  the  liquid  occupies  in  passing  through 
the  bed.  With  proper  aeration  and  distribution 
the   deeper   the  bed   the    better   should   the 
effluent   be,   but   each   cubic   yard  of   coarse 
material  performs  about  the  same  amount  of 
work  of  purification  whether  displayed  as  a 
deep  or  as  a  shallow  filter.     In  the  case  of  fine 
grade   material   experience    is   somewhat    in 
favour  of  using  a  given  quantity  of  medium 
as  a  shallow  filter,  as  suspended  and  colloidal 
matters  tend  to  retard  proper  aeration,  and  it 
has  been  found  that  by  far  the  greater  part 
of  the  purification  is  performed  in  the  top  3  ft. 
of  depth  of  the  filter  and  relatively  little  in  the 
lower   parts.     In   any   case,    however,   filters 
should  not  be  made  shallower  than  about  3  ft., 
as  imperfections  of  distribution  often  lead  to 
the  sewage  finding  direct  channels  or   short 
cuts  through  the  bed  and  so  reach  the  effluent 
channel  without  having  been  subjected  to  the 
necessary  bacterial  action.    This  is  particularly 
the   case   with  beds   of   coarse   material,  but 
with  a  6  ft.  depth  or  more,  any  inequalities  of 
distribution  are  dispersed  and  neutralised  by 
passage  through  the  deeper  stratum  of  filtering 
material. 


The  time  occupied  by  the  sewage  in  passing 
through  even  beds  of  9ft.  and  ]0ft.  depth  is 
usually  very  short  and  does  not  oftentimes 
exceed  about  5  minutes,  thus  showing  that 
the  process  of  nitrification  is  a  very  rapid  one. 
The  actual  rate  of  percolation  through  depends 
upon  the  grade  of  material  used,  the  condition 
of  its  surface,  whether  smooth  like  gravel  or 
irregular  like  clinker,  and  the  degree  to  which 
the  filter  has  matured  with  growths  of 
bacteria,  &c.  The  longer  the  sewage  takes  to 
percolate  through,  the  greater  the  purification 
to  be  expected,  assuming,  of  course,  the  bed  is 
in  good  working  condition.  Better  results,  too, 
are  obtainable  from  rough  surface  material 
like  hard  vitreous  clinker  than  in  the  case  of 
smooth  surface  stone  or  gravel  affording  less 
surface  for  contact  with  bacterial  growths. 

SURFACE  CLOGGING  OF  PERCOLATING  BEDS. — 
Should  the  surface  of  a  percolating  filter 
become  clogged  by  means  of  the  deposition  of 
suspended  or  colloidal  matters  or  by  pylobolus 
growth  causing  ponding  of  the  sewage,  the 
distribution  will  be  unequal,  aeration  will  be 
imperfect,  and,  as  a  result,  oxidised  nitrogen 
will  disappear  from  the  effluent  which  will 
become  putrescible.  Shallowness  in  depth  in 
the  case  of  fine  and  medium  grade  filters  has 
the  advantage  of  facilitating  aeration,  and  as 
the  proper  working  of  any  percolating  filter 
depends  on  the  free  passage  of  air  through 
the  bed,  the  bottom  layers  should  be  as  open 
as  possible  and  be  carried  on  an  aerating  tile 
or  hollow  floor.  Surface  clogging  may  be 
remedied  by  resting  the  filter  and  by  digging 
over  the  surface  with  a  fork  and  aerating  the 
filtering  material. 

At  some  places  much  trouble  is  experienced 
through  the  development  of  thick  gelatinous 
fungoid  growths  during  certain  parts  of  the 
year,  mainly  in  the  winter  and  early  spring, 
upon  the  surface  of  the  percolating  bed. 
These  cause  serious  "ponding"  and  deteriora- 
tion of  the  effluent.  It  has  been  suggested 
that  chemical  precipitation  liquors  favour  the 
growth  of  these  obstructions,  but  they  also 
occur  with  septic  tank  liquor.  As  a  remedial 
measure,  a  20  %  solution  of  caustic  soda  has 


411 


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ENCYCLOPAEDIA  OF 


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been  successfully  used  on  the  surface  of  the 
bed,  and  the  deposits  afterwards  washed  out 
in  the  effluent. 

DISTRIBUTION  ON  PERCOLATING  BEDS. — The 
spraying  of  sewage  on  percolating  niters  is 
more  liable  to  cause  nuisance  from  smell  than 
treatment  on  contact  beds,  but  this  is  very 
largely  avoided  by  completing  the  process  of 
purification  whilst  the  sewage  is  "  fresh  "  and 
so  avoiding  the  unnecessary  generation  of 
offensive  gases  as  occurs  when  the  sewage 
becomes  putrid  in  a  septic  tank.  During  the 
warm  months  of  the  year  there  is  often  con- 
siderable annoyance  from  flies  in  and  about 
percolating  filters. 

The  best  means  of  uniformly  distributing 
sewage  over  the  area  of  the  beds  is  an 
important  and  distinguishing  feature  of  the 
percolating  system,  to  which  too  much 
attention  cannot  be  paid  as  it  directly  affects 
the  quality  of  the  effluent  secured.  This 
subject  is  specially  dealt  with  under  the  head 
of  "  DISTRIBUTORS  "  (q.v.). 

Percolation  bed  effluents  are  generally 
better  aerated  than  those  from  contact  beds, 
and  are  of  a  more  uniform  quality.  The  first 
part  of  the  discharge  from  a  contact  bed  is 
generally  less  pure  than  the  average  discharge. 
The  percolating  filter,  too,  is  better  able  to 
cope  with  variations  of  flow  than  its  contem- 
porary the  contact  bed,  and,  per  cubic  yard  of 
filtering  material,  satisfactorily  treats  nearly 
double  the  quantity  of  tank  liquor. 

COMPARATIVE  COST  OF  PERCOLATING  AND  CON- 
TACT BEDS. — The  question  of  the  comparative 
cost  of  construction,  working,  and  maintenance 
of  percolation  and  contact  beds  respectively  is 
one  upon  which  but  little  information  of 
practical  service  can  be  given,  as  so  much 
depends  upon  local  conditions  and  require- 
ments. Every  case  must  be  decided  on  its 
merits  after  a  full  consideration  of  all  such 
local  circumstances.  It  may  be  stated 
generally,  however,  that  under  ordinary 
average  conditions  the  comparative  total 
annual  cost  of  completely  treating  a  given 
quantity  of  sewage  on  the  contact  and  per- 
colating systems  respectively  is  about  as  5  is 


to  3,  and,  unless  there  are  special  local  reasons 
to  the  contrary,  treatment  by  percolation  beds 
is  preferable.  The  expense  of  full  treatment, 
including  working  expenses  and  loan  charges 
for  preliminary  processes  and  oxidation  of  the 
tank  liquor  on  percolation  beds,  may  be  expected 
to  be  in  the  neighbourhood  of  £4  per  million 
gallons  dry  weather  flow. 

QUANTITY  TRKATED  PER  CUBIC  YARD  OF 
PERCOLATING  BED. — The  quantity  of  liquid 
which  can  be  satisfactorily  treated  per  cubic 
yard  of  capacity  of  percolating  bed  depends 
upon  the  strength  and  nature  of  such  liquid, 
whether  it  be  partially  settled,  well  settled, 
septic  tank  liquor,  or  precipitation  tank 
effluent.  The  clearer  and  more  free  from 
suspended  solids  the  liquor  may  be,  the  greater 
the  quantity  purified  per  cubic  yard  of 
filtering  material.  Crude  sewage  or  roughly 
settled  sewage  should  not  be  placed  upon  con- 
tact or  percolating  beds  if  trouble  from  choking 
is  to  be  deferred  or  avoided.  With  well-settled 
sewage  about  100  gallons  per  cubic  yard  of 
filtering  material  per  day  can  be  treated  on 
percolating  beds,  or  about  150  gallons  per 
cubic  yard  of  septic  tank  liquor  on  beds  of 
medium  grade  material.  With  clear  precipi- 
tation tank  liquor  as  much  as  from  BOO  to  500 
gallons  per  cubic  yard  per  day  may  be  treated 
according  to  the  strength  of  the  liquid.  In 
any  given  case  it  is  safest  to  find  by  actual 
trial  and  experiment  with  the  sewage  to  be 
dealt  with  the  maximum  work  that  can  be 
properly  got  out  of  a  given  quantity  of  filtering 
medium.  The  ordinary  rates  of  working  are 
very  commonly  doubled  when  the  sewage  is 
weak  as  in  times  of  storm.  The  past  require- 
ments of  the  Local  Government  Board  have 
not  recognised  any  superiority  of  the  con- 
tinuous filter  over  the  contact  bed  or  vice 
versa,  and  the  cubic  bulk  of  filtrant  must  be 
the  same  in  both.  The  maximum  volume  to 
be  treated  per  cubic  yard  of  filtrant  on  either 
process  is  calculated  at  168'7  gallons,  which 
provides  for  three  fillings  per  day  upon 
contact  beds,  or  for  continuous  or  intermittent 
discharge  upon  the  spray  or  percolating 
beds. 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


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AERATION,  OXIDATION,  AND  NITRIFICATION. — 
The  purification  of  sewage  is  not  entirely  a 
simple  question  of  oxidation,  but  is  of  a  more 
complex  and  variable  nature,  and  there  may 
yet  be  many  modifications  of  present  methods 
dictated  by  further  experience  in  the  future. 
It  appears,  however,  that  the  final  stage  of 
purification  should  be  one  of  full  aeration  with 
nitrification,  and  that,  generally  speaking, 
with  the  average  domestic  sewage,  the  best 
known  method  at  the  present  moment  for 
bringing  about  this  result  is  in  the  direction 
of  the  continuous  passage  of  the  tank  liquor 
through  something  akin  to  the  now  well-known 
"percolating  bed."  In  some  cases  it  is  pro- 
bable that  the  denitrification  changes  are 
equally  important  with  the  nitrification  change, 
as,  for  example,  for  the  effective  oxidation  of 
many  substances  such  as  cellulose,  and 
further  investigation  is  required  in  this 
connection. 

Whatever  may  be  the  method  of  puri- 
fication   adopted,    the    problem    resolves 
itself  largely  into  one  of  cost.     If  money 
were  no  object  a  town's  sewage  might  be 
converted   back   into   a    wholesome    drinking 
water,    but,     from    a     practical     standpoint, 
purification  is  carried  far  enough  when  taken 
well  within  the  limits  of  a  standard  of  safety 
appertaining   to    the   case   in  point,  and  the 
true  solution  of   this  difficult  problem  is    to 
bring    about    this    result    at    the    irreducible 
minimum  of  cost. 

REMOVAL  OF  SUSPENDED  MATTER  IN 
EFFLUENTS. — When  effluents  from  bacteria 
beds  contain  more  than  about  3  grains  per 
gallon  of  suspended  matter  some  special 
means  must  be  taken  to  secure  their  removal. 
This  is  done  by  straining,  settlement,  or  filtra- 
tion. Settlement  may  be  carried  out  by  slow 
passage  of  the  effluent  through  rectangular 
tanks  containing  a  number  of  baffle  plates 
and  submerged  divisions,  in  Dortmund  tanks, 
or  by  rapid  filtration  through  shallow  beds  of 
fine  clinker,  or  through  sand.  Although  a 
good  deal  of  the  suspended  matter  is  of  a 
light  flocculent  nature  and  subsides  but 
slowly,  a  sufficiently  clear  effluent  may 


usually  be  obtained  by  simple  settlement 
in  tanks  as  above,  but  if  a  clearer  water  is 
required  the  extra  labour  of  filtration  in 
addition  to  tank  settlement  must  be  incurred. 

TREATMENT  OF  SEWAGE  ON  LAND. — The  fifth 
report  of  the  Royal  Commission  on  Sewage 
Disposal,  dealing,  in  Part  III.,  with  the  purifi- 
cation by  treatment  on  land,  opens  with  the 
statement  that  "  there  can  be  no  doubt  that, 
where  the  soil  is  suitable  and  the  area  of  land 
sufficient,  the  organic  matters  in  sewage  can 
be  thoroughly  oxidised  by  land  treatment. 
This  fact  is  well  established,  not  only  by 
investigations  made  by  earlier  Commissions, 
but  also  by  wide  general  experience." 

Although  attention  has  been  largely  diverted 
during  recent  years  towards  other  modes  of 
treatment,  there  is  no  doubt  that  the  practical 


Valve 


Float 


Sludge 
OuOd 

FlG.  5. — Absolute  Eest  Tank.     (See  p.  4.) 

application  of  modern  advances  in  bacterio- 
logical knowledge  has  given  a  new  and 
increasing  interest  in  the  scientific  purification 
of  sewage  on  the  greatest  of  all  bacteria  beds, 
the  land.  Where  a  sufficient  quantity  of 
suitable  land  at  a  reasonable  price  can  be 
obtained,  this  still  remains  the  most  satis- 
factory method  of  disposal,  if  the  conditions  are 
favourable.  There  have  been  many  failures 
arising  in  connection  with  land  treatment, 
but  when  the  causes  are  investigated  often- 
times it  is  found  that  any  system  similarly 
abused  would  afford  no  greater  measure  of 
success.  The  biological  principles  involved 
have  been  not  infrequently  entirely  disregarded 
and  due  attention  has  not  been  paid  to  the 
capacity  of  the  land  in  respect  of  the  quantity 
of  sewage  that  can  be  satisfactorily  dealt  with 
thereon.  Another  fault  commonly  met  with 
is  that  of  localising  the  sewage  for  long  periods 
upon  certain  parts  only  of  the  total  sewageable 
area,  whilst  the  remaining  areas  are  reserved 
for  cropping  and  profit-earning  purposes.  In 


413 


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ENCYCLOPAEDIA   OF 


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other  words,  the  different  areas  are  not  suffi- 
ciently alternated  in  periods  of  work  and  rest. 
Former  sewage  "filters"  failed  by  choking 
owing  to  want  of  appreciation  of  the  necessity 
for  alternating  periods  of  rest,  and  all  land 
requires  like  opportunities  for  the  proper 
digestion  of  the  impurities  brought  upon  it. 
Suitable  cropping,  rest,  and  aeration  are  aids 
to  purification  and  especially  to  the  recovery 
or  cleansing  of  land  which  has  become 
"  sewage  sick "  through  being  overworked 
with  sewage. 

The  old  idea  of  returning  the  sewage  to  the 
land  for  the  sake  of  the  manurial  value  of  the 
organic  matter  contained  therein  has  long 
since  proved  to  be  a  profitless  pursuit,  owing 
mainly  to  the  small  quantity  of  such  organic 
matter  in  relation  to  the  volume  of  sewage  to 
be  treated. 

The  land  must  be  regarded  as  a  means  of 
disposing  the  sewage  of  the  town  it  serves, 
and,  given  proper  management,  whatever 
balance  there  may  be  on  the  wrong  side  of 
the  sewage  farm  account,  it  should  be  looked 
upon  as  the  cost  of  performing  the  important 
service  of  disposing  of  the  sewage  of  that 
town.  Every  effort  should,  of  course,  be  made 
to  keep  that  cost  as  low  as  possible  by  constant 
good  management  and  the  growing  of  saleable 
crops,  subject  always  to  the  efficient  purifica- 
tion of  the  sewage  for  which  purpose  the  farm 
was  brought  into  existence.  In  this  connec- 
tion it  should  be  remembered  that  when 
artificial  purification  works  are  once  adopted, 
there  will  be  nothing,  in  this  case,  to  come 
back  on  the  income  side  of  the  ledger  to 
lighten  the  cost  of  working  expenses.  A 
midway  course  is  frequently  found  advan- 
tageous from  many  points  of  view,  viz.,  to 
relieve  an  overworked  farm  by  constructing 
bacteria  beds  to  treat  the  dry  weather  flow  or 
a  considerable  proportion  thereof,  and  to  reserve 
the  land  for  treatment  of  storm-water,  and, 
if  necessary,  the  bacteria  bed  effluent.  This 
course  generally  results  in  a  greatly  improved 
effluent,  and  also  affords  facilities  for  the 
necessary  agricultural  operations  to  be  carried 
on  to  greater  advantage. 


Provided  it  is  properly  handled,  land  will 
continue  to  satisfactorily  purify  sewage  for  a 
practically  indefinite  period,  and  there  are 
many  farms  in  use  to-day  which  have  been 
satisfactorily  operated  for  purposes  of  sewage 
purification  for  the  past  30  years.  The 
sewageble  area  of  land,  however,  must  be 
increased  in  proportion  to  the  increase  in 
population  served  by  the  farm,  in  the  same 
way  that  any  other  works  require  to  be 
extended,  and  adjusted  from  time  to  time  to 
the  increasing  amount  of  work  demanded  of 
them.  But  it  is  just  at  this  point  that  it 
becomes  practically  impossible  to  deal  with 
the  sewage  of  large  populated  centres  by 
means  of  land  treatment,  and  also  in  many 
instances  to  extend  existing  farms  serving 
small  and  medium- sized  towns.  Under  the 
Local  Government  Board  Rules,  if  sewage  is 
treated  by  "broad-irrigation"  on  suitable  land, 
after  rough  screening,  the  requirements  are 
one  acre  of  land  for  every  150  of  the  popula- 
tion at  30  gallons  per  head,  that  is,  one  acre 
for  a  volume  of  4,500  gallons.  The  lands 
required  for  final  treatment  of  the  effluent 
from  bacteria  beds  is  one  acre  per  30,000 
gallons. 

Even  if  "  suitable "  land  could  be  found, 
calculating  upon  the  recognised  basis,  the 
areas  required  for  most  large  towns  become 
so  considerable  as  to  prohibit  the  continuance 
of  this  mode  of  disposal,  and  other  means  of 
dealing  with  larger  volumes  per  unit  of  area 
must  be  sought.  It  is  here  that  the  advantages 
of  the  modern  bacteria  bed  become  very 
pronounced,  as  a  means  is  thus  at  once  afforded 
of  concentrating  a  relatively  large  amount  of 
work  upon  a  small  area,  producing,  in  fact, 
what  may  be  regarded  as  an  intensified  land 
process,  occupying  but  a  small  fraction  of  the 
area. 

Much  careful  attention  has  been  given  to  the 
question  of  land  treatment  by  the  present 
Pvoyal  Commission  on  Se\vage  Disposal,  and, 
in  their  fifth  report,  when  comparing  effluents 
from  land  with  those  from  artificial  filters, 
the  Commissioners  state  that  "judged  by 
chemical  analysis  both  classes  of  effluent 


414 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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possess  similar  qualities.  As  regards  the 
eight  farms  which  we  have  had  under  observa- 
tion, the  average  purification,  calculated  on 
the  atmospheric  oxygen  used  up,  and  giving 
credit  for  the  oxygen  contained  in  the  effluent 
in  the  form  of  nitrate,  was  about  98  %.  It 
would  have  been  rather  higher  than  this  if 
the  suspended  solids  had  been  eliminated 
from  those  effluents  which  contained  them. 
As  regards  seven  contact  bed  plants  which 
we  have  examined,  the  average  purification 
on  the  same  basis,  but  eliminating  the 
suspended  solids,  was  93*4%.  As  regards 
six  installations  of  percolating  filters,  our 
analyses  show  that  the  average  purification, 
after  eliminating  the  suspended  solids,  was 
99'4%." 

The  Commissioners  further  state  that 
"  speaking  generally,  the  effluents  which  we 
have  examined  from  artificial  filters  as  at 
present  constructed  and  used  are  not  equal  in 
purity  to  effluents  from  the  best  land,  when 
treating  a  comparatively  small  quantity  per 
acre,  as  at  Nottingham  ....  Our  investiga- 
tions have  not  shown  that  there  is  any  essential 
bacteriological  distinction  between  effluents 
from  land  and  effluents  from  artificial  filters, 
though  effluents  from  land  usually  contain 
fewer  micro-organisms  than  effluents  from  the 
artificial  filters  which  are  at  present  in  use." 

QUANTITY  OF  SEWAGE  PER  ACRE  OF  LAND. — 
The  question  of  the  quantity  of  sewage  which 
can  be  treated  on  a  given  area  of  land  depends 
upon  the  strength  of  the  sewage,  the  quality 
and  depth  of  the  soil  and  subsoil,  whether 
filtration  or  surface  irrigation  is  followed, 
the  nature  of  the  cropping  of  the  land,  the 
amount  of  suspended  solids  in  the  sewage, 
and  the  nature  and  thoroughness  of  the  work  of 
preliminary  preparation  of  the  sewage  before 
passing  on  to  the  land.  Irrigation  without 
precipitation  is  inadvisable  owing  to  the  rapid 
choking  of  the  land  from  the  large  quantities 
of  solids.  Under  this  system  with  stiff  clay 
one  acre  per  25  persons  would  be  required  on 
the  average,  or  one  acre  per  100  persons  on 
loamy  gravel.  With  intermittent  filtration 
without  precipitation  on  sandy  gravel,  one 


acre  for  every  100  to  800  persons  would  be 
needed,  whilst  with  intermittent  filtration 
combined  with  precipitation  the  sewage  of  from 
500  to  600  persons  could  be  dealt  with  per 
acre  of  sandy  gravel.  In  the  case  of  broad 
irrigation  preceded  by  precipitation  on  clay, 
one  acre  for  every  200  persons,  and  one  acre 
for  every  400  in  the  case  of  loamy  gravel 
should  be  allowed.  Where  the  liquid  passing 
on  to  the  land  is  of  a  specially  well-prepared 
description,  such  as  is  obtained  by  precipitation 
followed  by  filtration  through  bacteria  beds 
or  specially  constructed  filters,  one  acre  for 
every  2,000  persons  should  suffice.  It  should 
be  understood  that  these  figures  represent 
what  may  be  expected  under  average  condi- 
tions, but  practical  experience  must  guide  the 
engineer  in  forming  his  opinion  of  the  sewage- 
treating  capacity  of  any  given  site.  Very 
commonly  about  four-fifths  of  a  surface  irriga- 
tion farm,  and  two-thirds  of  a  land  filtration 
farm,  is  resting,  it  being  assumed  that  the 
remaining  one-fifth  and  one-third  are  sufficient 
to  deal  with  the  sewage,  and  that  the  different 
sections  fall  in  for  sewaging  purposes  in 
rotation. 

In  regard  to  the  question  as  to  whether  a 
sewage  farm  is  dangerous  to  health,  the 
Commissioners  in  their  fifth  report  state  that 
"  no  proof  has  yet  been  furnished  of  direct  or 
wide-spread  injury  to  health,  in  the  case  of 
well-managed  sewage  farms."  It  is  interesting 
to  note  here  that  the  report  for  1905  on  the 
sewage  farm  of  Berlin  contains  the  following 
statement : — "  We  can  only  repeat  here  what 
we  have  said  in  previous  reports,  that  the 
sewage  treatment  has  had  no  injurious  effect 
upon  health."  This  farm  has  an  area  of  about 
39,000  acres  of  sandy  soil,  and  a  resident 
population  in  1905  of  4,198  persons. 

DISTRIBUTION  OVER  LAND.  —  The  main 
sewage-feeding  carriers  should  contour  the 
land  at  the  highest  possible  elevation,  so  that 
every  possible  part  of  the  area  may  be  brought 
within  "  flowing  "  range.  A  fall  of  1  in  500 
to  700  will  usually  be  sufficient  for  these  main 
carriers,  the  approximate  size  of  which  may  be 
about  18  in.  to  2  ft.  wide  by  about  18  in.  deep, 


415 


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SEW 


varying,  of  course,  according  to  the  quantity 
of  sewage  flow.  They  are  commonly  con- 
structed of  concrete,  brickwork,  concrete 
tubing  or  semi-circular  concrete  channels,  and 
sometimes  of  stoneware  channels.  The  latter 
are  rather  dangerous  for  cattle  in  some 
situations.  Outlet  chambers  with  valves  are 
provided  at  intervals  for  taking  off  branch  or 
supplementary  supplies  to  various  parts  of  the 


JZarihen, 
Ccdckwcrfer 


Collecting 
Drain, 


FIG.  6.— Sewage  Irrigation :  Catchwater  System. 

land  and  for  the  purpose  of  feeding  secondary  the 
distributing  carriers.  These  latter  are  usually 
cut  in  the  earth  along  contour  lines  at  different 
levels  down  the  slope  of  land  under  irrigation. 
The  position  of  the  earthen  carriers  are  varied 
from  time  to  time  according  to  the  areas  of 
land  to  be  irrigated. 

In  distributing  sewage  over  steep  ground 
what  is  known  as  the  "catchwater"  method 
is  employed,  in  which  the  earthen  carriers 
are  cut  at  short  intervals  of  level  along  contour 


irrigation  should  be  as  simple  and  cheap  as 
possible,  but  the  surface  should  be  well 
trenched  and  levelled,  with,  as  far  as  practi- 
cable, a  uniform  easy  grade.  There  should 
be  no  irregularities  of  surface  to  cause  ponding 
of  the  sewage  and  waterlogging  of  the  land. 
There  is  no  precise  line  of  distinction  between 
one  class  of  land  and  another,  but  all  kinds  of 
gradations  are  met  with  between  the  extremes 
of  light  sandy  loam  and  imper- 
vious clay.  Hand  trenching,  deep 
digging,  and  steam  ploughing  are 
the  most  effective  forms  of  culti- 
vation. 

CROPPING.  —  This    is    a    matter 
which  is  largely  influenced  by  local 
requirements,  but  almostall  ordinary 
crops  may  be  grown,  except  when 
volume  of  sewage,  as  is  sometimes  the 


Main, 
Carrier 


.  7. —Broad  Irrigation  :  Eidge  and  Furrow  System. 


case  with  broad  irrigation,  is  too  large,  or  the 
areas  available  too  restricted,  cereals  cannot 
be  grown,  and  the  crops  must  be  limited  to 
rye-grass,  mangold-wurzel,  osiers,  &c.     Some- 
times the  sewage  is  passed  through  beds  closely 
planted  with  duckweed,  American  water-weed, 
anacharis,  common  reed,  flowering  rush,  &c. ; 
beds  of  osiers  or  alder  trees  are  also  sometimes 
used,  but  the  soil  is  apt  to  become  overcharged 
with  organic  impurity  through  want  of  rest 
and     aeration,     and      the 
market  for    Ahe   cut   osiers 
is    now    not     so    good    as 
formerly.     Unless  there  is 
plenty  of  land  available  for 
sewage-flowing,    the    crops 
must   not   be    such    as    to 


lines,  so  that  as  the  water  flows  down  the  slope 
it  is  intercepted,  and  prevented  from  flowing 
off  the  land  to  the  final  outlet  carrier  before 
receiving  proper  treatment. 

In  the  case  of  broad  irrigation  over  flat  land 
with  heavy  soil,  the  "ridge  and  furrow" 
system  of  distribution  is  followed.  The  ridges 
are  about  33  ft.  apart,  and  the  furrows  have 
a  slight  fall  longitudinally.  Wet  soils  may 
be  greatly  relieved  of  excessive  moisture  by 
this  method. 

The  preparation   of    the    land  for    broad 


prohibit  the  use  of  the  land  for  sewage  pur- 
poses upon  an  emergency,  if  so  required. 
Eye-grass  absorbs  a  large  amount  of  moisture, 
but  in  many  districts  it  is  difficult  to  find  a 
sale  for  the  large  quantities  grown. 

UNDER-DKAINAGE.— Probably  the  best  class 
of  land  for  sewage  treatment  would  be  one 
consisting  of  a  surface  layer  of  alluvium  upon 
a  subsoil  of  porous  material,  such  as  chalk, 
gravel,  and  such  like ;  but  even  with  land  of 
this  description  it  will  be  necessary  to  see  that 
means,  either  natural  or  artificial,  exist  for 


416 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


SEW 


the  regular  removal  of   subsoil   water,   thus 
keeping   down    the   level   of   saturation,   and 
facilitating  the  penetration  of  air  as  deep  as 
possible  into  the  soil.     Aeration  and  drainage 
is   also    improved    by   deep    trenching    and 
ploughing,  which  greatly   assist   the   proper 
oxidation  of  the  sewage.     In  putting  in  under- 
drains  no  advantage  is  gained  in  laying  them 
deeper  than  from   3  to  4  ft.,  as  the  work  of 
purification  is  mainly  done  in  the  top  layers 
of  soil.     The  main  "pick-up"  drains  will,  of 
course,  often  need  to  be  placed  at  a  greater 
depth,    for    purposes    of     securing    suitable 
gradients.     It  is  very  undesirable  to  under- 
drain  clay  lands  at  all,  as  it  is  found  impracti- 
cable to  prevent  such  land  from  cracking,  and 
so  permitting  untreated  sewage  to  find  its  way 
down  to  the  drains.      The  draining  of  clay 
land   tends   to   increase    the    tendency   to 
crack.     Results  may,  however,  be  improved 
by  irrigating  the  lower  land  by  effluents 
from  the  upper  portions,  thus  securing  a 
double  or  treble  application.    Under-drains 
are    usually    laid   in   parallel   lines,    from 
half  a  chain  to  one  chain  apart,  and  are 
commonly   of   2  in.  diameter  agricultural 
butt    pipes,    12    in.    long.      About    660    of 
such   pipes   are    required    per    acre    if    laid 
one    chain    apart,    exclusive    of    the    larger 
sized  pick-up  drains  running  in  a  transverse 
direction.     Fine  ashes,  gravel,  or  surface  soil 
is  often  placed  around  the  under-drains,  to 
insure  filtration  through  a  certain  thickness 
of  material  before  reaching  the  drains.     Rats 
and  moles  should  be  constantly  trapped,  as 
their  burrows  allow  sewage  to  pass  away  to 
the  under-drains. 

INTERMITTENT  FILTRATION  is  the  system 
under  which  land  is  laid  out  in  level  beds, 
and  the  sewage  applied  thereto  at  regulated 
intervals  filters  downwards  through  the  per- 
vious soil  and  escapes  by  means  of  drains, 
or  through  a  porous  bed  of  gravel.  Clay  soils 
are  not  adapted  for  land  filtration.  Upon 
suitable  soils  the  sewage  of  about  1,000  persons 
per  acre  can  be  dealt  with.  The  distribution 
is  usually  done  by  ridge  and  furrows,  Fig.  8, 
so  as  to  secure  uniformity  of  application. 


The  positions  of  the  furrows  are  altered  every 
winter  or  early  spring,  care  being  taken  to 
avoid  placing  the  same  over  under-drains. 
After  efficient  precipitation  in  tanks  the  filtra- 
tion of  the  liquor  through  specially  prepared 
land  filtration  areas  should  yield  a  very  satis- 
factory effluent,  especially  where  the  land  is 
allowed  proper  rest,  and  frequently  dug  or 
ploughed  over. 

THE  SELECTION  OF  A  SYSTEM  OF  SEWAGE 
TREATMENT  depends  very  largely  upon  local 
conditions  and  requirements,  such,  for 
example,  as  the  character  of  the  sewage, 
the  price  and  facilities  of  obtaining  land, 
and  the  local  materials  available  for  con- 
structing artificial  filters.  In  the  fifth  report 
(1908)  of  the  Royal  Commission  on  Sewage 
Disposal,  some  observations  on  the  choice 


FlG.  8. — Intermittent  Filtration  :  Ridge  and  Furrow 

System. 

of  a  method  of  sewage  treatment  refer 
to  land  treatment  in  the  following  terms : — 
"  If  a  sufficient  quantity  of  good  land,  to  which 
the  sewage  can  flow  by  gravitation,  can  be 
purchased  for  about  £100  an  acre,  land  treat- 
ment would,  we  think,  usually  be  the  cheapest 
method  to  adopt.  Or,  if  the  case  were  one  in 
which  it  was  necessary  to  obtain  a  high  class 
effluent,  it  might  be  cheaper  to  pay  a  some- 
what higher  price  for  good  land,  rather  than 
to  adopt  artificial  treatment,  because  effluents 
obtained  from  the  treatment  of  sewage  on 
artificial  filters,  as  usually  carried  out  in 
practice,  are  generally  distinctly  inferior  to 
those  obtained  by  the  treatment  of  sewage  on 
good  land,  and  some  addition  to  the  ordinary 
artificial  plant  would  therefore  be  required. 
On  good  land,  a  sewage  of  average  strength, 
from  which  the  major  portion  of  the  suspended 
solids  have  been  eliminated  by  tank  treatment, 
can  be  treated  at  about  the  rate  of  30,000  gallons 
per  acre  per  day,  with  the  production  of  a  high 


M.S.E. 


417 


E  E 


SEW 


ENCYCLOPEDIA   OF 


SEW 


class  effluent.  If  the  land  available  were  of 
only  medium  quality,  capable,  say,  of  treating 
only  half  this  quantity,  its  use  might  still  be 
economical,  if  it  could  be  acquired  at  about 
.£50  an  acre.  In  cases  where  only  clay  land 
was  available  it  would  generally  be  cheaper 
and  more  satisfactory  to  provide  artificial 
filters."  Having  regard  to  the  fact  that  the 
disposal  of  sludge  is  an  important  factor  in  all 
methods  of  sewage  treatment,  this  aspect  of 
the  question  necessarily  largely  influences  the 
final  choice  of  a  system.  Continuous  flow 
tanks  and  septic  tanks  yield  less  sludge  per 
given  volume  of  sewage  than  would  be  derived 
from  chemical  precipitation  tanks,  and  the 
former  could,  therefore,  be  most  economically 
adopted  under  circumstances  where  it  was 
desirable  to  limit  the  output  of  sludge  as  far 
as  possible,  and  the  latter  where  fine  grade 
percolating  beds  are  proposed  to  be  adopted, 
upon  which  a  tank  liquor  as  free  as  possible 
from  suspended  matter  would  preferably  be 
used. 

The  question  of  the  possibility  of  nuisance 
from  smell  also  materially  affects  the  final 
choice  of  a  system,  and  in  this  connection 
contact  beds  would  probably  involve  less  risk 
of  nuisance  than  percolating  filters ;  but 
with  the  former  double,  and  in  some  cases 
treble,  contact  would  be  required  to  give  the 
necessary  degree  of  purity.  With  ordinary 
domestic  fresh  sewage  there  is  very  little 
risk  of  creating  nuisance  upon  percolating 
beds.  W.  H.  M. 

"REFERENCE. — For  further  information  on 
"  Sewage  Disposal,"  see  articles  : — 


A.B.C.  Process 

"  Absolute-rest "  Tank 

Aerobic  and  Anaerobic 
Treatment  of  Sewage 

Alumina  and  Lime 

Amine's  Process 

Analysis  of  Sewage 

Bacteriology 

Boston  Sewage  Purifica- 
tion 

Candy  Settling  Tank 

Colloidal  Matters  in 
Sewage 

Conder's  Sulphate  of  Iron 
Process 


Cosham  Tank 

Cultivation  Tank 

Dale's    Muriate   of    Iron 

Process 
Distributors 
Dortmund  Tank 
Dosing  Tank 
Dry-weather  Flow 
Ducat  Filter 
Dundrum  Tank 
Effluents 
Electrolysis 
Ferozone 
Ferrometer 
Fish  Life  in  Streams 


Hermite  Process 

Howatson  Process 

Hydrolytic  Tank 

International  Process 

Ive's  Tank 

Liernur  System 

Lime    and     Sulphate    of 
Iron 

Lime  Process 

Local  Government  Board 
Requirements 

London  Main  Drainage 

Manchester      Experts 
Report 

Manchester  Sewage  Dis- 
posal 

Micro-organisms  in  Sew- 
age 

Nitrification 

Ohio  Water  Supply  and 
Sewage  Disposal 


Oxidation  of  Sewage 

Oxynite 

Polarite 

Precipitating  or  Settling 
Tanks 

Richmond  Sewage  Dis- 
posal 

Rivers  Board  and  Central 
Authority 

Rivers,  Purification  of 

Royal  Commissions  on 
Sewage  Disposal 

Slate  Beds 

Sludge 

Spence's  Alumino-ferric 

Standards  of  Purity  (see 
Effluents) 

Storm  Water 

Trade  Effluents 

Wanklyn  and  Cooper's 
System 


Sewage  Disposal,  Royal  Commission 

on. — The  last  Royal  Commission  on  Sewage 
Disposal  was  appointed  on  7th  May,  1898. 
The  immediate  occasion  of  the  appointment 
of  the  Commission  was  the  unsatisfactory 
position  of  the  question  of  sewage  disposal, 
and  the  possibilities  opened  up  by  the  bac- 
terial processes  of  treatment  which  had 
recently  been  introduced.  The  Commis- 
sioners themselves  observe  that  in  many 
parts  of  England  the  pollution  of  rivers  went 
on  unchecked,  notwithstanding  the  fact  that 
the  Eivers  Pollution  Act  had  been  on  the 
Statute-book  for  over  a  quarter  of  a  century. 
This  state  of  affairs  was  partly  attributable  to 
a  deadlock  between  the  Local  Government 
Board  and  the  local  authorities,  due  to  the 
practice  of  the  former  of  declining  to  sanction 
any  loan  for  sewerage  or  sewage  disposal 
unless  provision  were  made  for  passing  the 
sewage  over  land,  and  the  impossibility  in 
many  cases  of  obtaining  land  of  suitable 
quality. 

The  Commissioners  have  examined  a  very 
large  number  of  witnesses,  inspected  many 
sewage  works  throughout  the  country,  and 
carried  out,  through  their  own  officers,  some 
important  experiments  and  investigations. 
They  have  already  issued  six  reports, 
comprising  in  all  twenty-four  volumes. 

The  first,  or   "Interim,"  report  appeared 


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on  12th  July,  1901.  In  it  the  Commissioners 
review  the  work  of  the  previous  Sewage  Com- 
missions which  were  appointed  between  1857 
and  1884,  and  state  certain  conclusions  of  their 
own.  They  recognise  that  peat  and  stiff  clay 
are  generally  unsuitable  for  the  purification 
of  sewage,  and  that  in  certain  cases  land 
treatment  is  impracticable.  They  express 
themselves  also  as  satisfied  that  it  is  prac- 
ticable by  so-called  "artificial"  processes  to 
produce  good  effluents  from  sewage,  either 
alone  or  mixed  with  certain  trade  refuse ; 
and  they  think  that  the  Local  Government 
Board  would  be  justified  in  modifying  their 
rule  calling  for  land  treatment. 

The    second   report    (issued   on   7th   July, 

1902)  consisted  of  a  series  of  reports  by  the 
officers   of   the  Commission,  relating  almost 
exclusively    to    the    influence     of    bacterial 
processes  on  disease  germs. 

The  Commissioners'  third  report  (2nd 
March,  1903)  deals  chiefly  with  trade  effluents, 
and  with  the  conflicting  state  of  the  law 
relating  thereto.  The  Commissioners  find 
that  sewage  containing  these  effluents  is 
generally  more  difficult  to  purify  than 
ordinary  sewage,  but  that  it  is  practicable,  in 
the  great  majority  of  cases,  to  purify  mix- 
tures of  sewage  and  trade  effluents  if  the 
manufacturers  adopt  reasonable  means  for 
removing  the  solids,  equalising  the  dis- 
charge, and  where  necessary  neutralising  the 
trade  effluent.  They  strongly  recommend 
the  creation  of  a  Central  Authority  to 
determine  differences  arising  between  manu- 
facturers and  local  authorities,  and  of  Rivers 
Boards  to  deal  with  questions  of  pollution 
and  other  matters  affecting  the  rivers  within 
their  respective  areas. 

The  fourth  report  (made  28th  December, 

1903)  deals  exclusively  with  the  pollution  of 
tidal   waters,   with   special   reference   to   the 
contamination    of    shellfish.      The   Commis- 
sioners reject  as  too  sweeping  the  suggestion 
that    all    sewage    should   be   purified   before 
being  discharged  into  tidal  waters,  but  they 
strongly    recommend    that    such    waters    be 
placed  under  the  jurisdiction  of  some  com- 


petent authority  having  power  to  prevent  the 
taking  of  shellfish  from  any  position  liable  to 
dangerous  contamination. 

The  fourth  report  was  accompanied  by  a 
series  of  five  volumes  containing  reports  by 
the  officers  of  the  Commission  on  the  general, 
chemical,  bacteriological  and  engineering 
aspects  of  the  land  treatment  of  sewage. 
The  reporters  found  that  the  effluents  from 
land  possess  a  bacterial  flora  characteristic  of 
sewage,  and  are  not,  from  a  bacteriological 
point  of  view,  in  a  proper  condition  for 
discharge  into  drinking  water  streams. 
Generally  speaking,  however,  those  effluents 
did  not  exercise  any  marked  prejudicial 
effect  on  the  streams  into  which  they  were 
discharged. 

The  fifth  report  (7th  August,  1908)  is 
separated  from  the  fourth  by  an  interval  of 
nearly  five  years.  The  volume  of  evidence 
which  accompanies  it  contains  a  compre- 
hensive record  of  the  methods  employed  and 
the  results  obtained  at  most  of  the  important 
sewage  works  throughout  the  country,  as 
well  as  of  the  opinions  held  by  those  engaged 
in  the  treatment  of  sewage  on  many  disputed 
points.  To  assist  them  in  forming  their  con- 
clusions the  Commissioners  also  carried  out  a 
series  of  experiments  of  their  own.  The 
following  are  the  more  important  of  the 
conclusions  arrived  at : — 

There  is  no  essential  distinction  between 
the  effluents  from  land  and  those  from  artifi- 
cially constructed  filters  :  the  effluents  from 
the  best  land  are  of  a  higher  class  than 
those  from  artificial  filters  as  at  present 
used  and  constructed;  but  the  effluents  from 
soils  which  are  not  well  adapted  for  the 
purification  of  sewage  may  often  be  very 
impure. 

Assuming  that  really  suitable  land  can  be 
purchased  at  £100  per  acre,  land  treatment 
of  sewage  is  probably  cheaper  than  artificial 
treatment. 

Chemical  precipitation  is  to  be  preferred  to 
simple  sedimentation  or  septic  treatment 
where  the  sewage  is  very  strong  or  contains 
much  colloidal  matter,  or  where  brewery  or 


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tannery  waste  is  present  in  such  quantities  as 
to  involve  the  risk  of  nuisance. 

The  effluents  from  trickling  filters  were 
found  to  be  more  uniform  and  better  aerated 
than  those  from  contact  beds,  and  it  was 
considered  that  a  cubic  yard  of  filtering 
material  arranged  as  a  trickling  filter  would 
generally  treat  about  twice  as  much  tank 
liquor  as  a  cubic  yard  of  material  in  a 
contact  bed. 

The  risk  of  nuisance  from  smell  is  greater 
with  trickling  filters  than  with  contact  beds, 
and  there  is  also  with  the  former  a  nuisance 
from  flies,  especially  if  the  filters  are  con- 
structed of  coarse  material. 

The  separate  system  of  sewerage  is  con- 
sidered suitable  only  for  villages,  country 
districts  and  suburban  areas,  where  there  is 
little  traffic. 

In  the  treatment  of  storm  water,  the 
Commissioners  recommend  some  radical 
departures  from  the  practice  which  had 
previously  been  enjoined  by  the  Local 
Government  Board.  Storm  water,  flowing  at 
too  great  a  rate  to  be  passed  through  the 
ordinary  tanks  and  filters,  should  be  sub- 
jected to  settlement  in  special  tanks,  and 
may  then  usually  be  discharged  without 
filtration.  The  provision  of  special  storm 
water  filters  is  condemned. 

They  are  strongly  of  opinion  that  questions 
as  to  the  amount  of  sewage  which  should  be 
filtered  in  storm  times,  and  also  as  to  any 
standards  which  may  be  adopted  for  effluents, 
should  depend  on  local  circumstances.  They 
deprecate  the  adoption  of  standards  of 
bacteriological  purity,  and  of  sterilisation 
processes,  both  on  the  score  of  cost,  and 
because  of  the  false  sense  of  security  which 
they  would  be  apt  to  engender. 

Having  dealt  with  the  question  of  the  puri- 
fication of  sewage  by  local  authorities,  the 
Commissioners  go  on  to  investigate  that  of 
the  disposal  of  trade  effluents  apart  from 
sewage.  Their  sixth  report  (dated  9th 
February,  1909)  is  concerned  with  the  dis- 
posal of  the  liquid  refuse  from  distilleries. 
Serious  complaints  had  been  made  of  the 


pollution  by  this  refuse  of  certain  rivers  in 
the  north  of  Scotland,  and  of  the  consequent 
injury  to  the  salmon  fisheries.  The  evil  had 
been  growing  rapidly  for  many  years,  and 
no  method  was  known  whereby  the  refuse  in 
question  could  be  effectually  purified  at  any 
reasonable  cost.  As  the  result  of  experiments 
of  their  own,  the  Commissioners  found  that 
a  satisfactory  effluent  could  be  obtained  by 
dilution,  treatment  with  lime,  and  filtra- 
tion through  trickling  filters.  In  the  case 
of  distilleries  situated  in  towns,  they  recom- 
mend the  admission  of  the  refuse  to  the 
sewers. 

The  investigations  still  in  progress  relate 
to  the  disposal  of  other  trade  effluents,  the 
question  of  standards  and  tests,  and  that  of 
the  manurial  value  of  sewage  sludge. 

The  keynote  of  the  Commissioners'  reports 
is  that  any  statutory  provisions  must  be 
elastic,  with  an  ultimate  appeal  to  a  pro- 
perly equipped  Central  Department  armed 
with  full  powers.  Not  the  least  important 
outcome  of  their  work  is  the  effective  demon- 
stration which  it  affords  of  the  extreme 
variations  in  the  composition  of  the  sewage 
of  different  towns  and  the  diversity  of  the 
conditions  under  which  it  is  discharged,  the 
failure  to  recognise  which  has  lain  at  the  root 
of  the  difficulties  which  have  been  experienced 
in  the  past.  Not  only  have  they  exposed  the 
ineffectiveness  of  many  of  the  particular 
regulations  which  have  hitherto  been  insisted 
upon,  but  they  have  shown  the  impossibility 
of  governing  the  future  disposal  of  sewage  by 
means  of  any  system  of  arbitrary  rules.  To 
quote  their  own  words : — "  Since  the  date 
of  our  appointment  considerable  develop- 
ments have  taken  place  in  regard  to  the 
disposal  of  sewage,  and  there  is  every  reason 
to  think  that  further  changes  will  occur  in 
the  future."  A.  J.  M. 

Sewage  Disposal  (Reports  on).— During 
recent  years  much  original  experimental  work 
has  been  carried  on  by  those  responsible  for 
the  design  and  working  of  sewage  purification 
works.  Such  reports  embody  practical  results 


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and  opinions  in  respect  of  the  experience  thus 
derived  and  form  a  useful  mass  of  literature 
which  has  contributed  largely  to  the  building 
up  of  a  more  widely  disseminated  knowledge 
of  bacterial  methods  of  sewage  purification. 
Amongst  others  may  be  enumerated  the 
following  examples  : — 

1.  Expert's   Report  on   the   Treatment   of 
Manchester  Sewage  (1899). 

2.  Report    on    Sewage    Disposal,    City  of 
Leeds  (1900). 

3.  Sewage  Disposal  at  Hanley  (1904). 

4.  Report  on  Sewage  Disposal,  Borough  of 
Leicester  (1900). 

5.  Annual  Reports  of  Rivers  Department, 
City  of  Manchester. 

6.  Reports    on    Sewage   Disposal,   London 
County  Council. 

7.  Report     on      Sewage     Purification     at 
Columbus,  Ohio  (1905). 

8.  Report  on  Sewage  Disposal,  City  of  Balti- 
more (1906). 

Sewerage. — General  Reference  to  Systems  in 
Use — Design  of  a  System  of  Sewerage — Maximum 
and  Minimum  Velocities  in  Sewers — General 
Principles  affecting  the  Design  of  Sewers — Exe- 
cution and  Supervision  of  Sewerage  Works 
— Materials  for  Sewerage  Works — Laying  of 
Pipe  Sewers — Brick  Sewers — Sewer  Accessories 
and  Details — Tank  or  Storage  Sewers — Inverted 
Siphone  —  Tumbling  Bays,  Ramps,  and  Drop 
Pipes — Storm  or  Relief  Overflows. 

GENERAL  REFERENCE  TO  SYSTEMS  IN  USE. — 
The  removal  of  the  sewage  of  towns,  consist- 
ing mainly  of  excreta,  liquid  household  and 
trade  wastes,  is  carried  out  upon  either  the 
"  conservancy  "  or  "  water  carriage  "  systems. 
The  former  method,  in  its  various  forms  of 
cesspool,  midden,  dry  earth,  and  pail,  having 
proved  itself  quite  unsuitable  for  use  in  large 
centres  of  population,  has  now  largely  given 
place  to  the  more  effective  "water  carriage" 
system,  with  which  the  present  article  is 
mainly  concerned.  Another  system,  which 
may  be  described  as  the  "  pneumatic  method," 
has  been  employed  to  a  smaller  extent.  By 
this  process  the  sewage  is  removed  by  com- 


pressed air  as  in  the  "  ejector  system  "  (see 
"EJECTORS"),  or  by  means  of  a  partial  vacuum 
created  in  small  sized  iron  mains,  as  in  the 
"  Liernur  "  method  (q.  ?•.). 

The  "  water  carriage  "  method  may  be  again 
subdivided  under  two  heads — the  "combined  " 
system  and  the  "  separate  "  system.  In  the 
former,  one  set  of  sewers  are  provided  for  the 
conveyance  of  all  sewage  matter,  slops,  rain 
water  from  roofs,  roads,  yards,  &c.,  whilst  in 
towns  drained  upon  the  "separate"  system 
duplicate  sewers  were  laid,  one  for  all  foul 
matters  and  liquids,  and  another  sewer, 
usually  the  larger  of  the  two,  for  the  removal 
of  storm-water  direct  to  the  nearest  natural 
outlet  or  watercourse.  Very  commonly,  it 
will  be  found  in  the  majority  of  towns  that  the 
older  parts  are  drained  upon  the  "  combined  " 
method,  whilst  the  newer  portions  are  pro- 
vided with  separate  sewers  for  sewage  and 
storm-water  respectively. 

In  districts  drained  upon  the  separate  sys- 
tem the  amount  of  sewage -reaching  the  outfall 
works  will  be  much  less  in  volume  and  more 
uniform  both  in  quality  and  quantity  than  in 
cases  where  duplicate  sewers  are  provided.  It 
will  be  stronger  and  probably  more  difficult  to 
treat,  but  much  depends  upon  local  conditions. 
Storm -water  troubles  at  the  outfall  works 
will  be  greatly  minimised,  but  care  must  be 
taken  that  the  outlets,  or  storm-outfalls,  are 
so  placed  as  to  avoid  nuisance  —  bearing 
in  mind  that  the  character  of  the  dis- 
charge therefrom  naturally  varies  according 
to  the  town  and  locality  from  which  it  is 
drained.  In  the  separate  system  the  soil 
sewers  do  not  receive  the  thorough  flushing 
during  storms  as  in  the  case  of  combined 
sewers,  but  they  may  be  designed  in  smaller 
diameters  involving  a  more  rapid  flow  of  the 
sewage  during  dry  weather  periods. 

In  many  instances  the  practice  has  been 
followed  of  converting  the  old  soil  sewers  into 
storm-water  sewers,  and  laying  in  a  new  sys- 
tem for  the  receipt  of  the  sewage  proper. 
This  may  be  done  where  the  existing  sewers 
are  sufficiently  sound,  but  in  many  cases  leaky 
storm-water  sewers  lead  to  serious  blockages 


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and  subsidences  in  the  roadways,  and  the 
policy  of  continual  patching  then  proves  to  be 
of  doubtful  economy. 

The  sewerage  systems  of  old  towns,  or  the 
older  parts  of  a  town,  usually  prove  to  be  much 
more  difficult  problems  to  deal  with  than  is 
the  case  with  modern  systems  of  drainage.  This 
is  especially  the  case  in  hilly  districts,  where 
often  the  sewers  are  laid  at  shallow  depths, 
at  steep  gradients,  and  are  subjected  to  serious 
wear  and  tear  by  the  swill  of  storm-water. 
The  exact  courses,  depths,  and  diameters  of 
the  sewers  are  often  unknown,  there  being  no 
reliable  record  available. 

THE  DESIGN  OF  A  SYSTEM  OF  SEWERAGE  must 
depend  largely  upon  local  conditions  and 
requirements,  but  there  are  certain  general 
principles  which  are  applicable  to  the  majority 
of  cases.  The  question  of  cost  is  a  leading 
determining  factor.  A  large  item  of  initial 
capital  outlay  may  be  justifiable  if  it  saves  a 
considerable  sum  in  annual  working  expenses. 
The  interest  and  repayment  charges  on  a 
gravitation  scheme,  for  example,  must  be  con- 
sidered against  the  annual  working  expenses 
of  a  pumping  scheme  of  less  initial  outlay. 
The  former  will  in  a  great  many  cases  be  the 
most  advantageous — but  there  are,  of  course, 
important  exceptions. 

In  designing  a  system  of  sewers  for  any 
district  some  of  the  principal  points  to  be 
considered  are :  the  area  of  the  district,  its 
geographical  contour,  levels,  and  convenience 
of  division  into  drainage  watersheds,  the 
nature  of  the  subsoil  in  which  the  sewers 
are  to  be  laid,  the  present  and  possible  future 
population  of  the  district,  the  wrater  supply, 
and  the  amount  of  the  average  annual 
rainfall. 

Other  important  factors  include  questions 
of  the  site  of  the  outfall  works,  best  course, 
and  possible  levels  of  the  outfall  sewer,  the 
relative  advantages  of  a  wholly  gravitation 
scheme  as  against  part  gravitation  and  part 
pumping,  or  as  local  conditions  may  deter- 
mine, and  the  necessity,  or  otherwise,  of  any 
special  works  peculiar  to  the  locality. 

The  population  of  a  district  generally  equals 


from  five  to  six  times  the  number  of  the  dwell- 
ing-houses, and  the  quantity  of  sewage  may  be 
reckoned  at  about  30  to  35  gallons  per  head 
per  24  hours,  provided  there  is  no  infiltration  or 
other  water  from  extraneous  sources  gaining 
access  to  the  sewers.  The  amount  of  the  water- 
supply  may  often  be  taken  as  a  rough  guide 
to  the  amount  of  sewage  to  be  dealt  with. 
The  proper  provision  to  be  made  in  designing 
the  sewage  system  for  future  growth  of  the 
district  drained  is  not  so  easily  arrived  at,  but 
comparisons  of  the  census  returns  for  several 
periods  will  give  a  good  guide  as  to  whether 
the  population  is  increasing,  stationary,  or 
declining.  (See  "POPULATION"  and  "VITAL 
STATISTICS.")  The  probable  development  of 
business  areas,  new7  factories,  and  works  and 
of  likely  residential  areas,  must  be  carefully 
considered. 

The  contour  and  levels  of  the  district  must 
be  fully  gone  into,  as  this  forms  an  important 
factor  in  the  selection  of  the  system  to  be 
adopted.  Where  pumping  has  to  be  resorted 
to  the  gradients  of  the  sewers  are  minimised 
as  far  as  permissible  in  order  to  reduce  the 
"  lift  "  at  the  pumping-station.  In  flat  dis- 
tricts the  pneumatic  or  ejector  systems  might 
be  found  advisable. 

The  amount  of  rainfall  to  be  admitted  to 
the  sewers  is  an  important  factor  in  deter- 
mining the  sizes  to  be  adopted.  One  inch  of 
rain  in  an  hour  should  prove  an  ample  allow- 
ance, as  this  amount  only  occurs  in  occasional 
severe  storms.  Any  increased  size  beyond 
that  necessary  to  convey  this  amount  would 
decrease  the  efficiency  of  the  sewers  under 
ordinary  conditions. 

In  settling  the  main  lines  of  sewers  the  site 
of  the  proposed  outfall  works  must  be  con- 
stantly kept  in  view.  Such  a  site  should, 
wherever  possible,  be  situated  at  a  level  to 
which  the  sewage  can  flow  by  gravitation,  and 
be  near  a  river  or  watercourse  into  which  the 
effluent  may  be  passed. 

MINIMUM  AND  MAXIMUM  VELOCITIES  IN 
SEWERS. — To  prevent  deposit  taking  place  a 
velocity  of  not  less  than  3  ft.  per  second  should 
exist  in  6  in.  to  9  in.  sewers ;  this  may  be 


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reduced  to  2J  ft.  in  12  in.  to  24  in.  sewers,  and 
to  2  ft.  per  second  in  larger  diameters.  These  are 
the  mean  velocities  :  the  minimum  velocity 
occurs  along  the  bottom  of  the  channel,  and 
may  be  taken  at  about  75%  of  the  mean. 
A  4  in.  drain  should  have  a  minimum  velocity 
of  1  in  36,  a  6  in.  diameter  1  in  70,  a  9  in. 
diameter  1  in  130,  and  a  12  in.  about  1  in 
250. 

As  a  maximum  velocity  the  flow  should  not 
exceed  from  4^  to  6  ft.  per  second  for  stone- 
ware pipes.  For  a  velocity  of  4  ft.  per  second 
a  4  in.  drain  requires  a  gradient  of  1  in  20,  a 
6  in.  diameter  1  in  39,  and  a  9  in.  drain  1  in 
75. 

GENERAL  PRINCIPLES  AFFECTING  THE  DESIGN 
OF  SEWERS. — Sewers  should  be  laid  true  in 
line  and  invert  from  point  to  point  with 
access  manholes  every  300  ft.  It  is  con- 
venient to  have  intermediate  lampholes  to 
facilitate  inspection  by  passing  down  a  light. 
In  setting  out  the  lines  and  levels  every  effort 
should  be  made  to  avoid  pumping  stations  or 
'•  lifts  "  of  any  description,  as  a  purely  gravi- 
tation scheme  will  generally  be  the  most 
economical  in  the  long  run.  Manholes  are 
also  necessary  at  all  changes  of  gradient  or 
direction,  and  at  all  junctions  of  branch 
sewers,  storm  overflows,  or  other  special 
points.  Where  a  sewer  unavoidably  passes 
under  a  railway,  stream,  building  or  other 
structure  there  should  be  a  manhole  on  each 
side  of  the  crossing  point,  except  where  the 
sewer  is  large  enough  for  a  man  to  walk 
through. 

Gradients  of  sewers  should  be  carefully  pro- 
portioned according  to  their  varying  diameters, 
doing  the  best  possible  with  the  fall  available. 
Excessive  fall  should  be  avoided,  or  damage 
to  the  sewers  will  result.  "  Drop-pipes  "  or 
"ramps"  at  the  manholes  and  tumbling- 
bays  are  employed  to  consume  excessive  fall 
where  such  exists. 

The  depth  at  which  sewers  should  be  laid 
depends  upon  the  description  of  property  to 
be  drained,  its  distance  from  the  roadway  on 
which  it  abuts,  and  ihe  depths  of  the  base- 
ments, if  any. 


Sewers  should  not  be  deeper  than  necessary, 
not  only  on  account  of  the  increased  cost,  but 
also  having  regard  to  the  greater  pressure 
or  weight  of  earth  upon  the  pipes,  and 
the  increased  expense  of  connecting  house 
drains. 

Where  streets  are  sewered  upon  the  "  separate 
system,"  it  is  customary  to  lay  soil-sewers  and 
storm-water  drains  side  by  side  in  the  same 
trench — the  storm-water  drain  being  generally 
at  a  higher  level.  It  is  important  in  most 
soils  that  the  lower  or  bottom  part  of  the 
sewer  trench  should  be  filled  with  concrete, 
or  the  earth  filling  stiffened  up  with  lime 
mixed  therewith  in  the  course  of  the  filling. 
The  pipes  should  be  supported  writh  concrete 
below  the  centre  line,  as  it  is  difficult  to 
secure  earth  filling  being  put  in  so  as  to  give 
adequate  support  to  the  lower  half  of  the  pipe- 
Should  there  be  any  weakness  at  this  point 
the  weight  of  superincumbent  earth  has  to  be 
carried  by  the  pipe  itself,  which,  if  of  stone- 
ware, may  very  probably-  be  crushed  under 
the  load  when  the  newly  filled  trench  settles 
down  upon  it.  Modern  heavy  traction-engine 
traffic  may  give  rise  to  sudden  movement  in 
a  sewer  trench  and  cause  the  pipes  to  move 
out  of  line  and  give  way  under  the  excessive 
load.  As  a  rule,  in  most  soils,  when  stone- 
ware pipes  are  laid  deeper  than  10  ft.  they 
should  be  surrounded  with  concrete,  to  give 
increased  strength  against  crushing  by  super- 
incumbent loads.  If  possible,  junctions  for 
house  connections  should  be  provided  when 
the  sewer  is  laid,  if  the  positions  can  be 
determined,  so  as  to  avoid  subsequent  dis- 
turbance of  the  sewer. 

Branch  or  tributary  sewers  should  connect 
with  the  main  sewers  at  manholes,  and  the 
junction  should  not  be  at  right  angles,  but  at 
an  inclination  or  sweep  leading  in  the  direction 
of  the  main  flow.  Where  bends  occur  extra 
fall  should  be  given  to  the  pipes  to  compensate 
for  friction,  and  the  inverts  of  tributary  sewers 
should  have  a  fall  or  drop  into  the  main. 

When  pipes  are  being  laid  careful  super- 
vision is  necessary  to  see  that  the  inverts  of 
the  pipes  are  true  and  even,  and  that  the 


423 


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ENCYCLOPAEDIA   OF 


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cement  jointing  does  not  protrude  inside  the 
pipes.  This  should  be  cleared  out  as  the 
laying  proceeds. 

Flushing  tanks  are  necessary  at  the  upper 
ends  of  sewers  having  flat  gradients.  Such 
tanks  are  best  fitted  with  automatic  flushing 
apparatus  regulated  to  discharge  at  fixed 
intervals. 

Manholes  on  soil  and  storm-water  sewers 
are  commonly  built  to  accommodate  and  give 
facilities  of  inspection  to  both  sewers  in  order 
to  save  the  expense  of  constructing  two 
separate  manholes.  In  the  case  of  combined 
manholes,  provision  should  be  made  to  pre- 
vent sewer  gases  ventilating  through  the 
storm-water  drains. 

Eoad  gullies,  whether  entering  soil  or  storm- 
water  drains,  should  always  be  trapped  at 
their  outlets.  They  are  constructed  of  brick- 
work internally  rendered  in  cement,  or  of 
stoneware  or  iron.  The  intervals  between 
periods  of  cleansing  such  gullies  depends 
upon  the  gradients  of  the  roadways  and 
the  amount  of  rainfall  occurring.  Large 
quantities  of  sand  are  washed  into  the  gullies 
in  hilly  districts,  and  frequent  emptying  is 
necessary. 

EXECUTION  AND  SUPERVISION  OF  SEWERAGE 
WORKS. — Upon  works  of  any  considerable 
extent  it  will  be  necessary  to  engage  a  resident 
engineer,  or  representative  deputed  from  the 
municipal  engineer's  staff,  to  supervise  the 
details  of  the  work  regularly  as  they  proceed. 
He  should  be  provided  with  a  small  temporary 
office  at  the  site  of  the  works,  and  it  will  be 
his  duty  to,  from  time  to  time,  set  out  the 
works  ahead  of  the  contractor's  workmen,  to 
define  the  centre  line  of  the  courses  of  the 
proposed  sewers  by  means  of  iron  or  wood 
pegs,  and  also  to  give  the  contractor  the 
correct  levels  to  which  he  is  to  work.  All 
levels  should  be  verified  by  comparison  with 
the  nearest  ordnance  survey  bench  mark,  and 
all  sight  rails  and  sewer  inverts  or  other 
levels  in  the  work  should  be  referable  to 
ordnance  datum.  Should  there  be  any 
deviation  from  the  original  plans,  either  in 
regard  to  level  or  line  of  work,  these  must 


be  carefully  recorded  on  the  plans  by  the 
resident  engineer  in  charge.  He  should  also 
keep  a  note-book  to  record  the  dates  of  pro- 
gress of  the  work,  to  insert  measurements  to 
any  special  junctions,  crossings  of  other  pipes 
or  work,  and  generally  any  matters  likely  to 
be  of  interest  and  utility  after  the  work  has 
been  covered  in.  It  will  be  the  resident 
engineer's  duty  to  examine  all  classes  of 
material  brought  upon  the  works,  to  condemn 
it,  and  order  its  removal  from  the  works  when 
found  inferior  in  quality,  or  to  report  to  the 
chief  engineer.  He  must  also  carefully 
examine  all  pipe  joints,  test  the  sewers  before 
allowing  them  to  be  covered  in,  and  generally, 
on  behalf  of  the  engineer,  to  keep  a  close  eye 
on  the  execution  of  every  detail  of  the  entire 
contract. 

MATERIALS  FOR  SEWERAGE  WORKS. — As  all 
works  of  sewerage  are  of  a  subterranean 
character,  subjected  to  considerable  pressure 
and  wear  and  tear  from  the  flowing  sewage, 
it  is  important  that  all  classes  of  materials 
used  should  be  of  the  best  obtainable. 

BRICKS. — Brickwork  in  sewers,  manholes, 
penstock  chambers,  and  other  sewage  work 
should  be  built  of  the  hardest  and  most 
impervious  bricks  obtainable,  and  be  laid  in 
cement  mortar.  The  "  backings  "  may  be  of 
good  hard  stock  bricks,  as  wire  cuts,  &c.,  but 
the  "  facings  "  should  be  of  best  blue  Stafford- 
shire bricks.  The  walls  of  settling-tanks 
should  also  be  faced  with  Staffordshire  blue 
bricks. 

CONCRETE  is  largely  used  for  foundations, 
bedding,  and  the  backing  of  brickwork ;  also 
for  forming  the  sewer  itself  in  the  case  of  the 
larger  diameters,  when  it  is  laid  in  situ  around 
centres.  Such  concrete  should  be  of  the 
cleanest  of  materials,  and  be  mixed  under 
experienced  supervision  and  care.  There 
does  not  appear  to  be  any  serious  deleterious 
action  by  the  sewage  upon  the  concrete. 
Concrete  is  greatly  used  also  for  settling- 
tanks  and  filter  beds.  When  in  large  areas 
it  is  very  liable  to  crack  ;  such  defects  have 
to  be  chased  out,  grouted  up,  and  pointed  in 
cement. 


424 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


SEW 


CONCRETE-TUBE  SEWERS  are  now  largely 
employed  both  for  sewage  and  storm-water 
purposes,  but  more  especially  the  latter.  The 
tubes  are  made  of  all  diameters,  from  12  in. 
upwards,  ai:d  will  be  found  less  costly  than 
stoneware  pipe  sewers  (12  in.  to  24  in. 
diameter),  and  much  cheaper  also  than  brick 
sewers  of  larger  diameters. 

The  tubes  are  made  of  concrete,  consisting 
of  crushed  granite  and  cement,  and  may  be 
obtained  either  "armoured"  or  unarmoured. 
Provided  the  concrete  is  of  high  class  and  of 
a  sufficient  thickness,  it  is  doubtful  if,  in  the 
long  run,  there  is  any  great  practical  advan- 
tage in  using  "  armoured "  concrete  tubes. 
There  has,  as  yet,  been  no  very  lengthy 
experience  sufficient  to  prove  that  the  metal 
placed  in  the  concrete  will  not  in  time  become 
more  or  less  oxidised,  and  so  split  or  weaken 
the  concrete.  The  latter,  it  has  to  be  remem- 
bered, is  practically  always  wet,  and  the  pre- 
vention of  such  oxidation  must  depend  largely 
upon  the  quality  of  the  concrete. 

PIPE  SEWERS  are  constructed  of  stoneware 
earthenware,  or  fireclay  pipes  ;  also  of  cast- 
iron  pipes  in  special  circumstances.  Earthen- 
ware and  fireclay  pipes  should  never  be  used 
for  public  sewerage  work,  as  the  material  is 
weak,  porous,  and  unreliable.  Fireclay  pipes, 
purporting  to  be  stoneware,  have  been  placed 
on  the  market,  but  the  broken  section  will 
appear  porous  and  prove  absorbent. 

Stoneware  pipes  are  very  generally  used 
for  the  great  majority  of  sewerage  and  drainage 
work.  The  materials  from  which  they  are 
manufactured  varies  in  different  localities, 
but  the  more  refractory  clays  are  employed, 
and  the  pipes  are  thoroughly  vitrified.  A 
broken  section  should  appear  dense  in  grain, 
have  a  metallic  ring,  and  be  non-absorbent. 
The  latter  quality  may  be  tested  by  observing 
the  effect  of  an  ink-line  drawn  on  a  fractured 
section  with  an  ordinary  pen;  if  the  ink 
spreads  and  rapidly  sinks  in,  the  material 
will  be  of  a  porous  character.  The  pipes 
should  be  even  in  thickness,  true  in  bore,  and 
be  well  "  salt-glazed  "  so  as  to  secure  a  lining 
approaching  natural  glass  as  near  as  possible. 


Soft  lead  glazes  are  quite  unsuitable.  When 
examining  a  consignment  of  stoneware  pipes 
every  pipe  should  be  gently  tapped  with  a 
hammer,  and  if  a  clear  metallic  ring  is  not 
produced  the  pipe  will  almost  certainly  contain 
a  crack  (though  sometimes  very  difficult  to 
find),  and  should  be  rejected. 

For  drainage  and  public  sewerage  work  the 
sizes  of  stoneware  pipes  used  are  generally  of 
6  in.,  9  in.,  12  in.,  15  in.,  and  18  in.  diameters. 
Larger  diameters  than  18  in.  are  not  advisable 
for  stoneware  pipes.  Beyond  this  size  concrete 
tubes  and  brick  sewers  should  be  used.  The 
thickness  of  material  in  stoneware  pipes  is 
commonly  as  follows  : — 

6  in.  dia.          .  f  in.  thick 

**       »»  J>  '  •          •»  5»  JJ 

19  1  1 

-*••"     it         »  •  *1     »          » 

-L"     5?        »  •       J-?     "          " 

I  Q  I  £ 

-1-0     »         »>  •  •       *8     »          " 

What  is  known  as  "  tested  "  stoneware  pipes 
are  largely  used  for  public  sewerage  work. 
These  pipes  are  specially  selected  and  tested 
under  a  considerable  head  of  water,  and  after- 
wards stamped  with  the  word"  tested  "  before 
leaving  the  maker's  worts.  They  cost  from 
15%  to  25%  more  than  the  ordinary  pipes. 

The  "specials"  in  stoneware  pipe  goods 
consist  of  bends,  junctions,  saddles,  channel 
pipes,  and  such  like.  Bends  should  not  be 
used  in  a  line  of  sewer,  but  all  changes  of 
direction  of  line  should  be  made  in  the  man- 
holes, so  that  the  sewers  may  be  thoroughly 
accessible.  Taper  pipes  should  be  used  for 
joining  sewers  of  different  diameters  and 
junction  pipes  for  connecting  up  branch 
drains.  Saddle  pieces  are  used  where  a  drain 
has  to  be  connected  to  the  main  sewer  after 
it  has  been  laid,  but  the  "  tapping  "  weakens 
the  sewer,  especially  if  done  upon  sewers  less 
than  12  in.  diameter.  Junction-pipes  should 
be  inserted  wherever  possible. 

JOINTS  IN  STONEWARE  SEWERS. — There  are 
many  patented  forms  of  joint  aiming  at 
better  alignment  of  the  pipes  and  perfect 
water-tightness.  The  many  forms  now  avail- 
able may  be  observed  from  the  manufacturers' 
catalogues  and  price-lists.  The  cost  of  the 


425 


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ENCYCLOPAEDIA   OF 


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pipes  is  invariably  greater  than  that  of  the 
ordinary  spigot  and  socket  type,  and  it  is 
doubtful,  except  possibly  under  some  special 
circumstances,  if  any  corresponding  advantage 
is  obtained  by  their  use.  For  the  great 
majority  of  sewerage  work  the  ordinary  spigot 
and  socket  joint  made  with  cement,  with  the 
inverts  carefully  levelled  and  the  insides  of 
the  pipes  wiped  out  at  each  joint  as  the  work 
proceeds,  will  be  found  to  produce  a  sound 
job. 

CONCRETE  AND  STONEWARE  PIPES. — Where 
the  foundation  is  bad,  concrete  should  be  laid 
to  give  a  sound  bed  for  the  pipes.  The  con- 
crete should  be  shaped  to  fit  the  body  of  the 
pipe  and  depressions  formed  to  receive  the 
sockets.  The  lower  half  of  the  pipes  should 
be  well  supported  by  the  concrete,  and,  if  laid 
in  a  deep  trench,  a  thickness  of  4  in.  or  6  in. 
should  be  carried  over  the  top  of  the  pipes  to 
relieve  the  pressure.  It  should  be  remem- 
bered, however,  that  by  so  doing  the  sewers 
are  rendered  less  accessible  for  purposes  of 
connecting  drains  thereto. 

CAST-IRON  PIPES. — Cast-iron  pipes  are  neces- 
sary in  certain  cases,  such  as  where  sewers 
are  laid  at  shallow  depths,  at  stream  or  rail- 
way crossings,  or  through  bad  ground.  The 
pipes  used  are  of  the  usual  water-main 
strength,  viz.: — 


Pipes. 

3"  dia. 

4" 

6" 

9" 
12" 
15" 
18" 


Thickness 
of  Metal. 


weig 

hing    1    cwt. 
H 
2| 
4" 

per 

pipe. 

lU 

14| 

All  pipes  should  be  tested  under  a  hydraulic 
pressure  of  600  ft.  head  of  water,  and  when 
under  test  rapped  sharply  with  a  hammer. 

Cast-iron  pipes  should  be  manufactured 
from  the  best  tough  grey  metal  from  the 
second  melting,  and  the  castings  should  be 
free  from  honeycomb,  spongy  places,  air  and 
sand  holes,  and  other  imperfections. 

Before  the  pipes  become  rusted  on  the  sur- 
face they  should  be  treated  whilst  hot  with 
the  Angus  Smith  solution,  consisting  of  a 


mixture  of  coal-tar,  pitch,  and  a  small  quantity 
of  linseed  oil  heated  to  a  temperature  of 
400°  F. 

The  jointing  of  cast-iron  pipes  is  usually 
done  with  molten  lead,  well  caulked  into  the 
joint.  "  Lead  wool  "  has  also  been  used,  and 
sometimes  a  "  rust  cement"  joint  consisting 
of  sal-ammoniac,  sulphur,  and  iron-filings  or 
turnings  mixed  to  a  paste  with  water. 

KEINFORCED  CONCRETE  SEWERS  LAID  in 
Situ. — Where  large  concrete  sewers  are  to  be 
constructed,  such  as  diameters  of  4  ft.  and 
over,  it  will  generally  be  found  more 
economical  to  build  them  in  situ  on  temporary 
centering  rather  than  transmit  large  diameter 
pipes  great  distances,  as  the  handling  of  such 
is  difficult  and  costly.  Local  materials  for  the 
concrete  aggregate  can  often  be  used,  but  it  is 
important  that  these  should  be  perfectly 
clean,  hard,  and  durable.  A  soft  aggregate 
will  result  in  a  porous,  weak  concrete,  and  a 
leaky  job. 

The  reinforcements  used  consist,  generally 
speaking,  of  a  permanent  sheet  centering, 
rolled  sections  or  rods  in  one  or  other  of  the 
various  forms  available,  or  of  a  meshwork  of 
some  description.  Expanded  metal  is  also 
used. 

The  "  Bonna  "  system  of  armoured  concrete 
tubes,  or  conduits,  has  been  used  in  France 
for  over  12  years  past,  both  for  sewage  and 
water  carriage,  and  has  given  satisfaction. 
The  system  has  also  more  recently  been  intro- 
duced into  this  country.  An  18  in.  armoured 
concrete  rising  main,  1  mile  in  length,  has 
been  laid  in  connection  with  the  Swansea 
Corporation  Waterworks. 

THE  LAYING  OF  PIPE  SEWERS. — The  trenches 
are  excavated  to  the  necessary  widths  and 
depths,  and  a  shaped  or  curved  bed  formed 
upon  which  to  lay  the  sewer-pipes,  care  being 
taken  that  they  are  evenly  bedded  throughout 
their  length,  and  not  allowed  to  rest  upon  the 
sockets  only.  The  pipes  should  be  truly  laid, 
both  as  regards  line  and  level,  in  vert  to  invert 
in  as  true  a  manner  as  possible.  The  proper 
gradient  of  the  invert  is  secured  by  setting  up 
"  sight  rails  "  at  convenient  intervals  (Fig.  !)• 


426 


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MUNICIPAL   AND    SANITAEY  ENGINEEEING. 


SEW 


The  ordnance  level  of  the  sewer  invert  through- 
out its  length  being  ascertained  from  the  plans, 
the  sight  rails  are  set  up  at  a  convenient 
height  of,  say,  10  or  12  ft.  above  the  invert, 
according  to  the  depth  of  the  sewer,  and  all 
intermediate  points  in  the  invert  of  the  pipe 
line  are  sighted  in  by  the  aid  of  "  boning 
rods  "  over  the  tops  of  adjacent  sight  rails. 

The  jointing  of  stoneware  pipe  sewers  . 
is    usually   done   in   cement  or  cement 
and  sand  (1   to  1),    a  piece   of   gasket      [^ 
or  twisted  yarn  being  first  coiled  round 
the   spigot   end  to  prevent  the  cement 
protruding  inside  the  pipes.     After  the 
joint  has  been  completed,  the  inside  of 
the  pipes  should  be  wiped  out  and  left 
perfectly  clear. 

The  filling  in  of  the  trenches  should 
be  carefully  done,  and,  in  order  not  to 
disturb  the  pipes,  the  finer  portions  of 
the  excavated  material  should  be  packed  ^ 
carefully  around  the  pipes,  and  over  £ 
their  tops,  to  the  depth  of  1  ft.  or  more 
and  carefully  rammed,  and  the  trenches 
then  filled  in,  in  layers  of  6  in.  to  9  in. 
thickness,  with  adequate  ramming  and 
watering,  if  necessary,  so  that  the  whole 
trench  may  become  thoroughly  con- 
solidated. The  pipes  are  greatly  sup- 
ported and  strengthened  by  packing  fine 
concrete  along  the  sides,  so  as  to  support 
the  lower  half  of  the  circumference ; 
but  this,  of  course,  considerably  adds 
to  the  cost. 

The  jointingof  concrete  tubes  is  simple. 
The   rebate   joints  are  covered  with  a    thin 
layer  of  Portland  cement  and  the  pipe  forced 
home.     The   joint  is  then  pointed  up  inside 
and  out,  and  left  neat  and  clean. 

BRICK  SEWERS  are  constructed  either  circular 
or  egg-shaped  in  cross-section.  The  circular 
form  is  the  strongest,  simplest,  and  most 
economical  form,  and  well  adapted  to  fairly 
large  and  continuous  flows ;  but  where  the 
volume  of  sewage  is  variable,  the  egg-shaped 
sewer  has  advantages,  owing  to  the  compara- 
tively small  wetted  perimeter  in  the  case  of 
small  flows.  The  standard  egg-shaped  section 


is  shown  in  Fig.  2,  and  a  new  form  of  this 
type  is  given  in  Fig.  3. 

The  thickness  of  brickwork  in  sewers  should 
not  be  less  than  9  in.,  and  may  be  determined 


by   the   formula 


-—_   =    thickness    in    feet, 


where  d  =  depth  of  excavation  in  feet,  and  r  = 
external  radius  in  feet. 


I— .         Sight  -real 


JZL 


Concrete 
support 

Liability  to  settlement, 
cUffitgAB.  Trench,  opposite. 
tol>e  fiHed-  -with,  weak 


itrifh.  earth,  and-  well 
rammed 


FIG.  1. — Section  of  Trench  for  Sewer  and  Stonn- water 
Drain,  showing  Concrete  Support  to  Pipes,  etc. 

The  inside  ring  of  brickwork  should  be  of 
the  hardest,  non-porous,  well-burnt  bricks, 
and  blue  Staffordshire  bricks  for  the  invert  as 
shown  in  Fig.  4  are  preferable  to  the  use  of 
hollow  invert  blocks. 

Invert  blocks  with  hollow  spaces  or  chambers 
as  illustrated  in  Fig.  5  are  not  recommended, 
especially  where  the  work  is  to  be  executed  in 
tunnel.  Unless  the  chambers  are  carefully 
filled  up  solid  with  concrete,  the  sewage  leaks 
out  into  these  passages  and  in  time  under- 
mines the  sewer.  Care  must  also  be  taken 
that  the  cement  used  in  such  filling  be  well 


427 


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ENCYCLOPEDIA  OF 


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"  cooled  "  by  spreading  on  a  floor  of  a  dry  shed 
for  a  week  before  being  used,  otherwise  the 
invert  blocks  may  be  burst  by  the  expansion 
of  the  concrete  in  setting,  thus  producing  a 
leaky  sewer  invert.  Blocks  having  a  rebated, 
or  spigot  and  socket  joint,  instead  of  a  plain 


_i 


FIG.  2. — Standard  Egg-shaped  Section  for  Brick 
Sewer. 

butt  joint  are  best.  Solid  blue  Staffordshire 
invert  blocks  are  also  advantageously  used  in 
egg-shaped  sewers.  For  circular  sewers,  an 
invert  of  the  best  blue  Staffordshire  bricks  as 
shown  in  Fig.  6  makes  the  best  job,  and  is 
more  conveniently  built,  especially  in  tunnel. 


FIG.  3. — New  Type  of  Section  for  Brick  Sewers 
suited  for  both  Small  and  Large  Flows. 

"  Cockrill-Doulton"  salt-glazed  tiles  have  been 
used  at  Great  Yarmouth  for  lining  the  sewer 
inverts,  the  tiles  being  fixed  by  means  of  tags 
embedded  in  the  concrete. 

Some  of  the  different  forms  or  sections  of 
sewers  which  have  been  adopted  in  practice 
will  be  of  interest  (see  Figs.  4  to  11).  The 


Clydebank  intercepting  sewers  at  Glasgow 
were  constructed  of  the  ordinary  circular 
section  (Fig.  7)  varying  from  3J  ft.  to  8  ft. 
in  diameter.  The  illustration  shows  a  6  ft. 
diameter  sewer  of  14  in.  brickwork  with  Port- 
land cement  concrete  foundation  and  backing. 


Six  courses  selected 
-Mae  Staff .  Ttricks 


?£•  -P.C.  concrete 

~~^~,  Vkie  StaffordsTiire 
~brick  invert  T?lock 

FIG.  4. — Main  Sewer,  Southampton. 

A  sewer  of  the  "  new  egg-shape "  form  is 
shown  in  Fig.  4,  as  used  in  the  main  sewers  at 
Southampton.  The  invert  is  of  blue  Stafford- 
shire blocks,  and  the  sides  adjoining  same  are 
of  six  courses  of  blue  Staffordshire  bricks.  The 
whole  of  the  brickwork  is  built  in  Portland 
cement  mortar. 

The    section    shown    in    Fig.   5    is    often 
adopted  in  waterlogged  ground.     The  subsoil 


Cement  rendering 


P.C.  concrete 


Stoneware  invert 
fitted  in. 
concrete 


nbsoH  drain, 


FIG.  5.  —  Section  of  Egg-shaped  Sewer,  showing 
use  of  Invert  Block  and  Subsoil  Drain. 

drain  is  necessary  for  the  removal  of  ground 
water  whilst  the  work  is  being  constructed. 

Fig.  8  is  a  section  of  a  branch  sewer  as 
adopted  in  Paris.  It  is  of  the  egg-shaped 
form,  provision  being  also  made  for  a  flat 
benching  or  path  along  which  sewer-men  can 


428 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


SEW 


walk,   whilst   the   narrow   channel   below   is 
suitable  for  small  flows. 

A  section  of  the  main  sewer,  Rue  de  Rivoli, 
Paris,  is  shown  in  Fig.  9.     A  narrow  channel 


1/r cement  rendering 


Concrete  carried,  up 
about  f.O"  above 
springing  Iwe 


Staffordshire  Vhie  Irricks 

JSxcazrated,  out  square 
•where  grraiatd  not 
thoroughly  satisfactory 


FIG.  6. 


for  small  flows  is  provided  between  two  walks, 
and  the  sewer  above  is  of  very  ample  section. 
They  are  also  utilised  as  subways  for  the 
underground  telegraph  and  telephone  wires, 
as  well  as  for  water-mains,  hydraulic  and 
pneumatic-power  pipes  placed  on  brackets  at 
the  sides  in  the  upper  part  of  the  sewer. 

The  new  Clichy  collecting  and  outfall  sewer 
is  shown  in  the  section,  Fig.  10.  Like  many 
of  the  Paris  sewers,  it  is  built  of  rubble 
masonry  with  an  inside  lining  of  Portland 


Sjf?  ~JP-  C.  concrete 


FIG.  7.— Clyde  Bank  Intercepting  Sewer,  Glasgow. 

cement,  and  an  outside  layer  of  cement  con- 
crete on  the  upper  part  of  the  exterior.  The 
usual  side  walks  are  also  provided  for  inspec- 
tion and  clearance  of  deposits,  &c.  A  part  of 
this  large  sewer  under  the  Boulevard  National 
was  constructed  in  tunnel  by  the  use  of  the 
shield.  The  cover  was  only  from  10  ft.  down 
to  2  ft.  4  in.  The  sewer  has  a  fall  of  1  in 
2,000,  or  about  2'67  ft.  per  mile. 


The  northern  outfall  sewer  for   conveying 
the  London  sewage,  on  the  north  side  of  the 
Thames,   from    the    Abbey    Mills    Pumping 
Station  to  the  Metropolitan  Outfall  Works  at 
Barking  is  shown  in  Fig.  11.     It  con- 
sists of  three  9  ft.  by  9  ft.  culverts  side 
by  side,  laid  with  a  fall  of  2  ft.  per  mile 
on  a  bed  of  concrete.     For  a  distance 
of  about  1*5  mile  in  the  neighbourhood 
of  Barking  the  structure  is  carried  on 
brick  arches  supported  on  concrete  piers, 
passing  down  through  the  peat  to  the 
gravel.     The  culverts  are  encased  in  an 
embankment  of  earth  raised  above  the 
low-lying  marshes,  over  which  they  cross 
and  carry  a  roadway  on  the  top. 
SEWBE    ACCESSORIES    AND   DETAILS. — Man- 
holes  should   be  provided  on   sewers   at  all 


FIG.  8. — Branch  Sewer  Pans. 

changes  of  line  or  gradient,  and,  in  any  case, 
not  less  frequently  than  100  yards  apart. 
They  should  be  built  of  9  in.  brickwork  set 


FIG.  9. — Main  Sewer,  Eue  de  Eivoli,  Paris. 


429 


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ENCYCLOPAEDIA  OF 


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in  cement,  and  may  be  rectangular  or  circular 
in  plan.  A  good  method  when  adopting  the 
rectangular  plan  is  to  give  the  walls  a  slight 
curve  concave  on  the  inside,  which  gives 
additional  strength  and  also  increases  the 
working  space  within  the  chamber.  Cast  or 


(hick 


Side 
walk. 


drain. 


FIG.  10.— Clichy  new  Outfall  Sewer,  Pans. 

wrought  iron  foot-irons  are  built  into  the 
walls  to  facilitate  access  to  the  chamber.  The 
invert  of  the  manhole  is  usually  formed  in 
concrete  with  strong  glazed  channel  pipes. 
A  combined  sewer  and  storm-water  man- 
hole is  shown  in  Fig.  12.  Where  a  number 
of  branch  sewers  at  various  angles  unite 
at  one  chamber,  manholes  of  special  design 


FIG.  11. — Northern  Outfall  Sewer,  London. 

to  suit  the  case  become  necessary.  The 
roofing  in  of  the  manhole  chamber  is  also 
occasionally  a  matter  of  some  difficulty, 
especially  where  the  sewer  is  shallow,  and  the 
headroom  necessary  for  the  usual  manhole 
arch  is  not  available.  A  flat  or  shallow  con- 
^truction,  such  as  obtained  by  girders  and 
armoured  concrete,  becomes  necessary  in 
order  to  give  adequate  room  within  the  man- 
hole, and  at  the  same  time  sufficient  strength 
to  carry  the  street  traffic. 


Lampholes  are  sometimes  provided  midway 
between  the  manholes  placed  at  100  yard 
intervals  on  a  pipe-sewer.  They  are  useful 
for  lowering  a  light  to  facilitate  inspection, 
but  are  not  often  of  much  service  on  brick- 
sewers,  these  being  generally  large  enough  for 
a  man  to  pass  through. 


Sewer. 


Wt  door 


Storm 
water 


SECTION    ON  A.B. 


A-  - 


FLUSHING  CHAMBERS  AND  APPARATUS.  - 
Flushing  is  frequently  necessary  in  sewerage 
systems  owing  to  flatness  of  gradient  or  limited 
use  of  the  sewers.  Sewers  laid  on  new  estates 
are  sometimes  not  called  upon  for  many 
years  to  convey  sufficient  sewage  to  keep 
them  thoroughly  clean,  and  frequent  flushing 


430 


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MUNICIPAL  AND   SANITAEY  ENGINEERING. 


SEW 


is  needed.  This  is  accomplished  in  various 
ways  :  (a)  by  hose  discharging  down  the  man- 
hole ;  (b)  by  lowering  a  penstock  in  the  man- 
holes and  thus  heading  up  the  sewage  flow 
and  flush  water  to  a  certain  height,  and  then 
suddenly  discharging  the  same  in  order  to 
give  the  sewer  a  thorough  scour ;  (c)  by  pro- 
viding special  flushing  chambers  at  the  head 
of  all  sewers  having  flat  gradients  and  fitting 
the  chambers  with  flushing  penstocks,  or, 
better  still,  with  automatic  flushing  siphons, 
which  can  be  regulated  to  discharge  at  stated 
intervals  according  to  requirements.  Such  a 
flushing  chamber  is  shown  in  Fig.  13.  The 
requisite  capacity  of  these  tanks  depends  a 


( Manholes \ 


FIG.  13. — Flushing  Chamber,  with  Automatic 
Siphon-discharge. 

good  deal  upon  the  circumstances  of  the  case, 
but  about  400  gallons  will  be  advisable  for 
9  in.  sewers,  500  to  600  gallons  for  12  in. 
sewers,  700  to  800  gallons  for  15  in.,  and 
about  1,000  gallons  for  18  in.  In  large  inter- 
cepting or  collecting  sewers  there  is  usually  a 
sufficient  depth  of  flow  to  keep  them  clear  of 
deposit.  Underground  flush  tanks  are  con- 
structed of  brickwork,  backed  with  concrete  or 
clay  puddle  according  to  circumstances,  the 
inside  faces  of  the  brickwork  being  rendered  in 
Portland  cement  so  as  to  insure  a  thoroughly 
water-tight  job.  Bituminous  sheeting,  such 
as  Callender's  and  others,  will  also  be  found 
a  useful  means  of  securing  water-tightness. 

There  are  a  number  of  automatic  siphons 
on  the  market  suitable  for  use  in  underground 
flush  tanks  as  above.  In  some  types,  the 
water  as  it  accumulates  gradually  displaces 
the  air  in  the  siphon,  whilst  in  others  the  air 


is  confined  and  compressed  by  the  accumu- 
lating water  until  it  blows  off,  and  thus  induces 
siphonic  action. 

For  small  flushes  not  exceeding  100  gallons, 
metal  tipping  buckets  are  occasionally  used 
for  flushing  in  sewer  manholes,  but  are  not 
so  satisfactory  as  the  automatic  flush  siphon 
above  referred  to.  The  tipping  buckets  are 
pivoted  on  bearings  fixed  in  the  brickwork  of 
the  manhole,  and  are  so  arranged  that  when 
the  water  supply  has  dripped  into  the  buckets 
to  a  certain  height  the  centre  of  gravity  is 
upset,  and  the  contents  of  the  tipper  are  pro- 
jected forward  down  a  sloping  benching  into 
the  sewer.  When  empty,  the  bucket  or  tipper 
reinstates  itself  and  the  refilling  proceeds  as 
before. 

SEWER  IRONWORK. — In  connection  with  all 
sewerage  work  a  considerable  amount  of  iron- 
work of  various  kinds  is  employed,  such  as  in 
penstocks,  valves,  sluices,  tide  and  flap  or 
back-flow  valves,  valve  and  penstock  gearing, 
step-irons,  landings,  manhole  covers,  and 
so  on. 

TANK  OR  STORAGE  SEWERS  become  necessary 
where  a  free  and  continuous  outlet  for  the 
sewage  flow  cannot  be  provided,  as  in  the  case 
of  a  sea  outfall  or  low-lying  district,  from 
which  the  sewage  must  be  pumped.  In  the 
case  of  sea  outfalls  the  sewage  cannot  usually 
be  discharged  at  high-tide,  nor  is  it  desirable 
to  do  so  at  low-tide  when  the  sewage  would 
probably  have  to  run  over  a  portion  of  the 
foreshore  and  cause  a  nuisance.  It  is  more 
commonly  necessary  to  discharge  only  when  the 
tide  is  at  the  ebb,  and  provision  must  be  made 
for  the  accommodation  of  the  sewage  accumu- 
lating at  the  outfall  until  it  can  be  discharged. 
The  size  of  storage  required  depends,  of  course, 
upon  the  quantity  of  sewage  and  storm  water 
to  be  dealt  with,  but,  as  the  ebb  occurs  twice 
in  the  24  hours,  very  large  tanks  will  not 
usually  be  necessary,  unless  the  volume  of 
liquid  is  excessive,  or  other  local  necessities 
obtain.  Fig.  14  shows  a  chamber  on  the 
junction  of  a  4  ft.  6  in.  by  3  ft.  egg-shaped 
outfall  sewer  with  a  tank  or  reservoir  sewer 
7  ft.  6  in.  in  height  suitable  for  a  sea  outfall. 


431 


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ENCYCLOPAEDIA  OF 


SEW 


The  tank  is  of  the  nature  of  a  widening  out 
or  enlargement  of   the   outfall  sewer  and    a 


Tc&tfccr 
Reservoir 


FIG.  14. — Chamber  at  Junction  of  Outfall  and 
Tank  Sewers. 

valve  is  provided  to  prevent  a  back-flow  of 
sewage  and  sewer  air  from  the  tank  into  the 
town  outfall  sewer. 

INVERTED  SIPHONS  are  necessary  where 
the  line  of  sewer  must  cross  some  obstruc- 
tion, such  as  a  stream,  railway,  or  subway 
occurring  at  such  a  level  as  to  prevent  the 
sewer  following  the  proper  hydraulic  gra- 
dient. Such  siphons  are  to  be  avoided, 
but  when  necessary  should  be  made  as 
accessible  as  possible.  In  the  case  of  a 
stream  or  canal  the  pipes  of  wrought  iron 
or  of  boiler  plate  are  commonly  laid,  from 
a  line  of  barges  arranged  across  the  stream, 
in  a  trench  dredged  in  the  bed  of  the 
stream  and  afterwards  covered  over  with 
gravel,  &c.  Such  pipe  lines  should  be  laid 
in  duplicate,  and  communicate  on  each  side  of 
the  stream  with  a  roomy  penstock  chamber  to 


give  facility  for  frequent  clearing  of  the 
siphons,  which  is  invariably  necessary.  At 
the  upper  chamber  a  storm  overflow  should 
be  provided  so  as  to  relieve  the  siphon  of 
excessive  pressure  at  storm  times.  When 
sewers  necessarily  cross  canals,  railways,  and 
bridges,  arrangements  must  be  made,  well  in 
advance,  with  the  various  authorities  owning 
such  works,  and  their  requirements  as  to 
terms,  conditions,  and  details  of  construction 
at  such  crossings  must  invariably  be  complied 
with.  The  work  must  be  done  in  the  most 
permanent  and  stable  manner,  especially  in 
the  case  of  railway  crossings. 

TUMBLING  BAYS,  RAMPS,  DROP  PIPES. — These 
are  different  methods  of  overcoming  excessive 
fall  in  lines  of  sewers  in  hilly  districts. 
Tumbling  bays  are  objectionable  on  account 
of  the  direct  fall  breaking  up  the  sewage  and 
tending  to  cause  nuisance  by  the  discharge 
of  sewage  gas.  A  better  method  of  connecting 
between  a  high-level  and  low-level  sewer  is  by 
means  of  a  "  ramp  "  constructed  in  connection 
with  a  manhole  as  shown  in  Fig.  15.  The 
ramp  or  "  drop  pipe "  should  have  a  wide 
mouthed  junction,  and  preferably  be  of  cast- 
iron. 

STORM  OR  RELIEF  OVERFLOWS. — Provision  for 
relief  of  internal  pressure  in  sewers  in  times  of 
heavy  rain  is  very  essential,  especially  in  hilly 
districts,  and  also  in  cases  w?here  the  sewers 
carry  both  sewage  and  storm  water.  The  most 


FIG.  15. — Eamp  and  Manhole. 

favourable  position  to  make  such  provision  is 
at  a  point  on  the  system  where  several  sewers 


432 


SHA 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


SIN 


from  the  higher  districts  converge.  The  over- 
flow usually  consists  of  a  pipe  or  brick  weir 
placed  at  a  certain  height  above  the  sewer 
invert,  in  order  that,  when  a  dilution  of,  say, 
six  times  the  ordinary  flow  has  been  reached, 
the  surplus  water  passes  out  or  over  the  storm 
weir  direct  to  the  nearest  watercourse.  The 
adjustment  of  storm  overflows  in  a  manner  so 
as  to  insure  a  uniform  degree  of  dilution  or 
of  strength  of  sewage  water  passing  over  is  a 
matter  of  some  considerable  difficulty,  seeing 
that  the  strength  of  the  dry  weather  sewage 
itself  is  very  variable  throughout  the  24 
hours,  e.g.,  the  character  of  the  liquid  pass- 
ing over  a  fixed  weir  in  the  middle  of  the 
night  when  the  sewage  proper  is  weak  would 
be  very  different  from  that  escaping  over  such 
weir  at  say  10  to  11  a.m.,  when  the  ordinary 
sewage  flow  is  at  its  maximum  volume  and 
strength. 

REFERENCE  should  also  be  made  to  the 
articles  "  CONSERVANCY  SYSTEM";  "FLOW  IN 
PIPES  AND  CONDUITS  "  ;  "  DRAINAGE  (HOUSE)  "  ; 
"DRY  WEATHER  FLOW"  ;  "EARTH  CLOSETS"  ; 
"EJECTORS";  "FLUSHING  SEWERS  AND 
DRAINS  "  ;  " LAMPHOLES  ";  "LIERNUR  SYSTEM"; 
"LONDON  MAIN  DRAINAGE  "  ;  "  PENSTOCK  "  ; 
"  PIPE-JOINTS  ";  "  PIPES,  CAST-IRON  AND 
STONEWARE  ";  "  SEPARATE  SYSTEM  "  ;  "  SEWERS 
AND  DRAINS  "  ;  "  SUBSOIL  DRAINAGE  "  ;  TEST- 
ING DRAINS  AND  APPARATUS";  "VENTILATION 
OF  SEWERS  AND  DRAINS  "  ;  "  WATER-CARRIAGE," 
&c.  W.  H.  M. 

Shallow  Wells.     (See  "  WELLS.") 
Shone's  Ejectors.    (See  "EJECTORS.") 


Shone's  System  of  Ventilation. 

"VENTILATION  OF  SEWERS.") 


(See 


Sight  Rails.— Sight  rails  are  used  for  the 
purpose  of  obtaining  true  gradients  for 
sewers,  drains,  &c.  Uprights  are  fixed  at  the 
sides  of  the  trench  at  convenient  points  and 
the  "  sight  rails  "  nailed  thereto",  with  their 
upper  edges  (which  must  be  level  and  per- 
fectly true)  at  a  fixed  height  above  the  invert 
of  the  work.  For  convenience  in  sighting 

M.S.E.  433 


they  are  often  painted  in  alternate  bands  of 
black  and  white.  At  least  three  sight  rails 
should  always  be  in  place  in  each  length  of 
the  work,  so  that  any  displacement  of  either 
of  them  may  be  at  once  detected. 

The  levels  of  the  work  are  obtained  from 
the  sight  rails  by  means  of  "  boning-rods  " — 
each  consisting  of  two  pieces  of  light  scant- 
ling nailed  together  in  the  form  of  a  T,  the 
length  of  the  longer  piece  being  equal  to  the 
depth  from  the  top  of  the  sight  rail  to  the 
bottom  of  the  work.  In  use  a  boning-rod  is 
held  upright  in  the  trench,  and  raised  or 
lowered  until  the  top  of  the  cross-piece  on  it 
is  in  exact  alignment  with  the  tops  of  the 
rails.  The  bottom  of  the  rod  then  gives  the 
required  level  for  the  work.  In  laying  pipe- 
sewers  two  rods  will  be  required — one  for  the 
bottom  of  the  trench,  and  the  other  for  the 
pipes.  The  latter  should  have  a  short 
L-shaped  foot  to  rest  on  the  invert  of  the 
pipe,  and  the  pipe  is  raised  or  lowered  until 
the  top  of  the  rod  is  in  "correct  alignment. 
(See  Fig.  1  under  article  on  "  SEWERAGE.") 

A.  J.  M 

Sinks. — The  classes  of  sinks  in  general  use, 
of  each  of  which  one  or  more  may  have  to  be 
provided  in  large  houses,  are  : — 
Scullery  Sinks,  Pantry  Sinks,  Nursery  Sinks, 
Drip  or  draw-off  Sinks,  Larder  or  Dairy  Sinks, 
Vegetable  Sinks,  Pickling  Troughs,  Wash- tubs 
and  Housemaids'  Sinks. 

These  should  all  be  chosen  in  accordance 
with  the  uses  to  which  they  are  to  be  put. 

SCULLERY  SINKS  must  be  governed  in  dimen- 
sions by  the  size  of  the  premises  in  which 
they  are  fixed  and  the  amount  of  washing-up 
to  be  done.  They  are  best  made  of  glazed 
stoneware — white  or  cane — and  should  have  a 
plug  and  overflow  so  that  they  may  be  filled 
with  water.  In  large  premises  they  are  best 
provided  in  pairs — one  for  the  washing  of 
plates,  and  the  other  for  rinsing  them. 

PANTRY  SINKS,  in  which  glass  and  silver  are 
washed,  may  be  constructed  of  lead-lined 
wood,  as  this  material  is  less  liable  to  cause 
damage  than  fireclay  or  stoneware.  They 

F  F 


SIP 


SIP 


have  the  drawback,  however,  that  under  the 
constant  use  of  hot  water  the  lead  is  liable  to 
buckle  up,  twist,  and  crack.  Stoneware  sinks 
are  therefore  frequently  used,  a  wooden  bowl 
being  provided  in  them  for  the  actual 
washing. 

NURSERY  SINKS,  for  soaking  and  washing 
soiled  baby-linen,  should  be  of  white  glazed 
stoneware,  and  should  have  plugs  and  over- 
flows. They  should  be  comparatively  deep. 

DRIP  SINKS  fixed  under  taps,  for  drawing 
water  for  the  bedroom,  may  consist  of  shallow 
glazed  stoneware  or  lead  trays  on  the  floor. 

LARDER  AND  DAIRY  SINKS  should  be  of  stone- 
ware, white  glazed  inside  and  out.  They 
should  be  deep,  have  rounded  corners,  and  be 
provided  with  plugs  and  overflows. 

VEGETABLE  SINKS  AND  WASH-TUBS  should 
be  deep,  have  plugs  and  overflows,  and  should 
be  made  of  picked  American  birch,  pine,  teak, 
or  sycamore,  with  tongued  and  grooved  joints 
drawn  together  with  iron  bolts  and  screws  out- 
side the  sinks.  They  are  best  provided  in 
pairs — one  for  washing,  and  the  other  for 
rinsing. 

PICKLING  TROUGHS  may  be  made  in  the  same 
way  as  vegetable  sinks,  or  of  slate  slabs 
similarly  jointed  ;  or  they  may  be  of  glazed 
fireclay,  care  being  taken  that  the  glazing  is 
such  as  is  not  acted  upon  by  salts  or  acids. 

HOUSEMAIDS'  SINKS  should  be  of  white  glazed 
fireclay,  and  provided  in  conjunction  with 
"  SLOP  HOPPERS,"  for  which  see  under  that 
heading. 

Siphon. — A  siphon  consists  of  a  pipe  or 
tube  bent  to  form  two  legs  of  unequal  length, 
by  means  of  which  a  liquid  may  be  conveyed 
over  an  intermediate  elevation  to  a  lower  level. 
It  is  used  for  emptying  casks,  cisterns,  &c.,  or 
for  drawing  water  from  one  reservoir  to  another 
at  a  lower  level,  where  suitable  conditions 
obtain.  The  action  of  the  siphon  depends 
entirely  upon  the  pressure  of  the  atmosphere 
forcing  the  liquid  up  the  shorter  leg,  whilst 
the  excess  of  weight  of  the  liquid  in  the  longer 
branch  causes  the  flow.  To  explain  this 
action  it  is  assumed  that  the  siphon  is  filled 


with  water  and  the  short  leg  immersed,  as  in 
figure.  Then,  the  pressure  acting  at  C 
forcing  the  liquid  up  the  tube  is  the  atmo- 
spheric pressure,  less  the  weight  of  the  column 
of  liquid  D  C.  Also,  the  pressure  at  B  is  that 
of  the  atmosphere  minus  the  weight  of  the 
column  A  B.  But  as  the  leg  A  B  is  longer 
than  C  D,  the  pressure  at  B  is  less  than  that 
at  C,  so  that  a  flow  takes  place  from  C  to  B 
in  proportion  to  the  difference  between  the 
pressures  at  C  and  B,  and  the  greater  the 
difference  between  these  two  levels  the  more 
rapid  the  flow.  The  siphon  will  not  work  if 
the  height  C  D  exceeds  that  of  a  column  of 
liquid  which  balances  the  atmospheric  pres- 
sure. The  limit  of  such  height  would  be 
about  34  ft.  for  water  and  30  in.  for  mercury. 
The  siphon  is  started  by  filling  it  with  liquid, 


Siphon. 

closing  the  ends,  and  immersing  the  shorter 
leg  as  shown,  when  a  flow  will  take  place  from 
the  free  end  at  B.  Or,  it  may  be  charged  with 
water  and  started  by  closing  end  B,  exhaust- 
ing the  air  from  the  siphon  by  means  of  a 
pump,  when  the  water  will  rise  through  the 
end  C  and  flow  to  B. 

INVERTED  SIPHONS  are  largely  employed  in 
engineering  works,  such,  for  example,  as  on 
aqueducts  or  pipe-lines  for  water  supply  pur- 
poses where  a  deep  valley  has  to  be  crossed, 
or  where  it  may  be  necessary  to  carry  the  pipe- 
line under  the  bed  of  a  river,  the  two  ends  of 
the  inverted  siphon  coinciding  with  the 
hydraulic  grade  line  of  the  aqueduct. 

Siphonage  (of  Traps.)— One  of  the  most 
frequent  causes  by  which  the  water  seal  of 
badly  ventilated  traps  is  destroyed ;  the 


434 


SIT 


MUNICIPAL   AND    SANITAEY  ENGINEEBING. 


SIT 


siphonage  of  the  trap  being  brought  about  by 
the  discharge  of  another  fitting  on  the  same 
waste-pipe,  or  by  the  momentum  or  impetus 
of  the  water  passing  through  the  trap  itself. 
The  latter  is  most  likely  to  take  place  where 
the  waste-pipe  is  of  considerable  length.  To 
prevent  siphonage  ventilation  is  essential.  In 
the  case  of  a  long  waste-pipe,  on  which  is  only 
one  fitting,  the  ventilation  of  the  waste-pipe 
will  be  sufficient.  Where  more  than  one 
fitting  discharge  into  a  waste-pipe  common  to 
all,  each  trap  except  the  highest  on  the  stack 
must  be  separately  ventilated,  the  various  vent- 
pipes  being  conveniently  branched  into  a  main 
anti-siphonage  pipe.  Ventilation  pipes  must 
be  branched  into  the  outlet  side  of  the  traps  at 
a  point  removed  a  few  inches  from  the  crown 
of  the  latter,  and  should  be  curved  at  the  point 
of  connection  in  the  direction  of  the  flow 
through  the  waste-pipes. 

Sites  of  Houses. — Soil. — Surroundings.— 
Aspects.— Planning. — Maisonettes  and  Flats. — 
It  is  not  always  possible  to  select  the  site  of  a 
house,  especially  in  towns,  but  in  this  case 
preference  should  be  given  to  a  gravelly  soil 
and  high  ground,  to  open  squares,  or  to  wide 
roads  running  north-east  and  south-west,  or 
north-west  and  south-east,  and  to  the  sunny 
side  of  the  way.  Avoid  houses  built  on  made 
ground,  or  see  that  the  site  is  covered  with 
6  in.  of  concrete. 

SOIL. — When  choice  can  be  exercised,  the 
soil  should  be  naturally  dry  and  well  drained, 
elevated  somewhat  above  the  surrounding 
district,  but  not  bleak.  The  spur  of  a  hill  is 
better  than  the  sloping  sides.  Clay  is  imper- 
vious, damp  and  cold,  and  if  a  clay  site  is 
unavoidable  the  highest  ground  should  be 
chosen.  If  a  thin  layer  of  sand  or  gravel 
rests  on  a  subsoil  of  clay,  it  is  to  be  avoided, 
as  the  rise  and  fall  of  the  subsoil  water  will 
cause  movement  of  the  ground  air,  and  when 
this  is  expelled  it  is  unhealthy.  Ground 
water  should  not  be  nearer  the  surface  than 
4ft. 

SURKOUNDINGS. — The  neighbourhood  of  a 
marsh  is  unhealthy  from  the  damp  and  the 


malarial  vapours  which  may  arise.  Brick- 
fields, gas-works,  chemical  factories,  soap 
works,  and  similar  places  give  off  effluvia- 
which  are  decidedly  unpleasant  and  may  be 
deleterious  to  health.  Factories  pollute  the 
air  with  smoke  and  some,  such  as  copper 
works,  destroy  the  vegetation.  Cesspools,  if  un- 
avoidable, should  be  at  least  50  ft.  away  from 
a  dwelling,  should  be  built  of  brick-in-cement 
and  rendered  on  the  inside  to  prevent  pollution 
of  the  surrounding  soil.  Wells  should  be  on 
the  highest  ground  available  and  carried  down 
with  impervious  sides  deep  enough  to  reach 
pure  water  only. 

ASPECT. — The  house  should  be  so  situated 
that  the  sun  and  air  have  free  access  to  it, 
and  it  should  be  so  placed  that  all  sides  are 
exposed  to  the  sun  at  some  period  of  the  day. 
It  should  not  be  too  closely  surrounded  by 
trees  ;  deciduous  trees  in  large  numbers  in  the 
neighbourhood  of  a  dwelling  render  it  damp. 
A  pine  wood  is  not  open  to  this  objection.  As 
a  rule  no  tree  should  be  nearer  to  a  house  than 
its  own  height ;  within  a  distance  of  20  ft.  the 
roots  are  liable  to  disturb  the  drains  and 
foundations  of  the  walls.  Large  trees  in 
moderation,  afford  shelter  from  high  winds, 
and  are  thus  useful,  especially  on  the  north 
and  east  sides. 

PLANNING. — North-west  is  a  good  quarter 
for  the  house  to  face,  and  the  rooms  may  be 
appropriated  according  to  the  light  required. 
The  larder  and  store-rooms  may  face  north, 
more  or  less,  so  as  to  be  kept  cool ;  the  w.-c.'s 
may  face  north  to  east,  so  that  there  is  no  hot 
sun  on  the  outside  soil  pipe  to  cause  excessive 
expansion  and  contraction ;  the  bath-room 
may  face  east  to  get  the  early  morning  sun ; 
the  breakfast-room  and  morning-room  should 
face  south-east  to  south  so  as  to  be  bright  and 
cheerful  in  the  morning;  the  dining  and 
drawing-rooms  should  face  south-west  to  west 
to  get  the  afternoon  sun ;  the  kitchen  and 
scullery  should  be  on  the  cool  side  of  the 
house  but  receive  a  fair  amount  of  sunlight, 
say  east  to  south-east ;  the  principal  bedrooms 
should  face  north-west  and  the  back  bedrooms 
east  to  south-east.  A  north  aspect  is  suitable 


435 


F  F  2 


SLA 


ENCYCLOPEDIA   OF 


SLA 


for  a  study,  library,  or  work-room,  where  a 
steady  diffused  light  is  appropriate ;  a  bay 
window  may  often  form  a  cosy  nook,  where 
the  sun  may  reach  one  of  its  sides. 

MAISONETTES  AND  FLATS. — Maisonettes,  or 
houses  containing  two  or  four  separate 
dwellings,  are  not  generally  unhealthy,  but 
modern  west-end  "  mansions  "  or  flats  should 
be  avoided  ;  it  is  difficult  to  get  thorough 
ventilation  without  draught,  and  the  basement 
flats  are  little  better  than  cellar  dwellings. 
"Back-to-back"  houses  should  be  avoided  at 
all  costs.  H.  A. 

Slate  Beds  for  the  Primary  Treatment 
of   Sewage. — The  original   coarse    coke   or 
clinker   contact   beds   were   designed  for  the 
primary   treatment   of    screened    sewage    in 
order  to  render  the  liquid  portion  fit  for  final 
treatment  on  land,  fine-grained  contact  beds, 
or  other  suitable  method.     The  coarse  beds 
allowed  the  smaller  suspended  matters  to  pass 
into  the  interstices  between  the   coke,    and, 
settling  there,  served  as  food  for  the  various 
organisms    which    rapidly   accumulated,   the 
proposal   being   an   alternative   to   the    then 
generally  prevailing  method  of  chemical  treat- 
ment and  sludge   pressing.     The  result  was 
entirely  satisfactory,  and  in  the  absence  of  any 
improvement  would  still  form  the  only  method 
for  effecting  the  inodorous  destruction  of  those 
matters  which,  in  their  collective  form,  consti- 
tute "  sludge."      It  was  found,  however,  that 
after   some   few   years   the    resulting    debris 
arising   from    the    destruction   of   the    solid 
organic  matters  were   retained   between   the 
particles  of  coke,  &c.,  and  gradually  reduced  the 
working  power  of  the  beds.    This  action  called 
for  a  remedy.     In  addition,  it  was  observed 
that  with  coke  or  similar  material  there  are  a 
number    of    particles    of    solid    matter   pre- 
senting only  an  outer  surface,  the  interior  of 
each  particle  being  wasted.     It  was  obvious 
that   if   each   particle   was   hollow   it   would 
present   an   interior   as   well   as   an  exterior 
surface  on  which  sewage  matters  could  deposit, 
and  thus  greatly  increase  the  water  content 
of  the  bed. 


These  considerations  suggested  the  use  of 
agricultural  drain-pipes,  but  the  fact  that  a 
pipe  is  only  a  bent  plate  pointed  at  once  to 
the  feasibility  of  using  superposed  plates, 
which  would  form  a  series  of  shelves  on  which 
the  sewage  particles  could  settle,  and  be 
digested  by  the  innumerable  variety  of 
organisms,  from  bacteria  to  worms,  which 
would  speedily  develop. 

The  following  illustration  will  demonstrate 
the  process  :— 

GENESIS   OF    THE    PLATE    BACTEEIA   BED. 


Section  of  Coke 
Bed  showing 
wast i'  spare  in 
centre  of  parti- 
cles of  coke — 
and  deposit  on 
surface  of  coke. 


Section  of  Pipe 
with  deposit  on 
upper  surfaces  of 

exterior  and  in- 
terioz-,  thus  se- 
curing double 
working  capa- 
city and  surface. 


Pipe  cut  at  A  and 
opened  out  tint, 
forming  a  plate. 


The  dark  line  on  the  surface  of  the  plate  indicates 
the  layer  of  "living  earth"  rapidly  formed  by  the 
decomposition  of  the  sewage  deposit,  which  layer 
receives  an  increment  of  about  one-hundredth  of  an 
inch  at  each  filling  of  the  bed  with  normal  sewage. 
Tliis  freshly-deposited  thin  layer  is  consequently 
rapidly  attacked  by  the  organisms  (worms,  infusoria, 
moulds,  and  bacteria)  in  the  "living  earth,"  and 
thereby  reduced. 

Fig.  1. 

436 


SLA 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


SLA 


It  was  finally  decided  to  use  the  '  waste 
slate  debris '  from  quarries,  the  slates  being 
cheap,  absolutely  permanent,  capable  of  being 
easily  and  thoroughly  cleansed  at  any  time  if 
necessary,  thus  restoring  the  bed. 

An  experimental  bed  was  constructed  at 
Devizes,  Wilts.,  by  the  co-operation  of  the 
town  council  and  worked  for  19  months. 
The  crude,  unscreened,  and  unsettled  sewage 
arriving  at  the  outfall  was  used  to  fill  the  bed 
two  or  three  times  daily,  with  the  result  that 
the  solids  were  reduced  to  an  inoffensive 
residue,  which  on  exposure  to  the  air  dried 
without  nuisance  of  any  kind  to  a  condition 
resembling  garden  mould. 

The  greater  portion  of  this  residue  came 
away  from  the  slate  bed  during  the  last 
portion  of  the  discharge,  and  could  be  easily 
collected  instead  of  being  allowed  to  flow  on 
to  the  surface  of  the  fine  clinker  bed  which 
received  the  effluent  from  the  slate  bed.  The 
humus  in  the  bulk  of  the  slate  bed  effluent 
went  on  to  the  fine  bed,  where  it  was  retained 
and  scraped  off  from  time  to  time. 

In  consequence  of  the  method  of  constructing 
the  slate  bed  with  layers  of  slate  about  a  quar- 
ter of  an  inch  thick,  separated  by  blocks  of  slate 
2  in.  cube,  the  water  capacity  of  the  bed  is,  when 
new,  about  85%  of  the  total  cubic  content  of  the 
bed.  After  a  time  the  average  depth  of  debris 
and  organisms  on  each  slate  is  about  another 
quarter  of  an  inch,  which  reduces  the  total 
working  capacity  to  about  70%,  the  net  result 
being  that  the  slate  beds  need  be  only  one  half 
the  size  of  the  old  coke,  &c.,  contact  bed, 
thereby  effecting  a  saving  of  nearly  50%  in 
the  constructional  cost  of  the  tank,  which, 
when  filled  with  slate,  forms  the  "  bed." 

The  continued  use  of  the  method  at 
Devizes,  where  it  has  been  treating  the  whole 
of  the  sewage  unsettled  and  unscreened  since 
12th  September,  1905,  and  at  other  places 
under  varying  conditions  of  strength  of  sewage, 
manufacturing  waste,  &c.,  has,  in  the  opinion 
of  the  writer,  demonstrated  the  fact  that  the 
beds  show  no  tendency  to  become  choked, 
the  resulting  residue  escaping  from  the  beds 
as  rapidly  as  it  is  formed. 


The  grit  which  arrives  with  the  sewage  is 
largely  retained  in  the  channel  supplying  thev 
inlets  to  the  slate  beds,  and  is  removed  from 
time  to  time  with  a  spade,  the  work  involved 
being  but  slight.  The  working  cost  at 
Devizes  has  been  reduced  from  £700  per 
annum  under  the  old  system  of  chemical 
precipitation  and  sludge  pressing  to  £200  per 
annum,  with  the  further  advantage  of  removing 
all  cause  of  complaint  as  to  the  condition  of 
the  brook  receiving  the  effluent. 

From  the  results  of  5  years'  work  with 
this  system  the  conclusion  may  be  drawn 
from  many  different  independent  investiga- 
tions with  sewages  of  widely  varying  quality 
that  it  is  not  only  effective,  but  is  a  valuable 
means  of  dealing  with  the  sludge  problem 
and  preparing  the  liquid  portion  of  the  sewage 
for  secondary  treatment.  The  material  will 
not  break  down  when  once  properly  built  in 
the  beds,  nor  can  the  drainage  from  the  under 
surface  of  the  bed  be  impaired ;  whilst  the 
growth  of  the  organisms,  will  take  place  on 
both  surfaces  of  the  slates  or  other  material 
used  as  "  plates,"  and  will  not  choke  up  the 
spaces  between  the  respective  layers  as  in  the 
case  of  coke,  &c. 

Evidence  is  accumulating  to  show  that  the 
beds  are  self-cleansing  for  the  reasons  men- 
tioned, the  capacity  of  beds  steadily  working 
for  4  years  having  undergone  no  material 
change  after  the  first  6  months. 

During  the  winter  months,  in  consequence 
of  the  sluggish  action  of  the  organisms,  there 
is  a  tendency  for  the  deposit  to  accumulate, 
but  with  the  arrival  of  the  spring,  when  all 
vegetable  and  animal  life  is  most  active,  the 
beds  rapidly  discharge  their  accumulated 
burden  of  humus,  &c.  This  action  in  no 
way  impairs  their  working  power,  as  the 
quantity  of  matters  accumulating  is  only  a 
small  proportion  of  the  total — in  conse- 
quence of  the  temperature  of  the  beds  being 
to  a  considerable  extent  self-generated 
and  retained  after  the  manner  of  the 
ordinary  gardener's  "  hot-bed,"  i.e.,  by  the 
vital  processes  of  the  organisms  at  work 
therein. 


437 


SLA 


ENCYCLOPEDIA  OF 


SLA 


In  order  to  illustrate  by  concrete  examples 
the  action  which  takes  place  in  these  beds,  the 
writer  has  carried  out  the  following  series  of 
experiments  on  the  rate  of  destruction  of  some 
typical  food-stuffs  when  submitted  to  the 


ordinary     deposited    matters    in    settlement 
tanks. 

If  a  portion  of  the  deposit  is  placed  on  a  small 
piece  of  slate,  aboiit  3  in.  or  4  in.  square  for 
convenience,  or  other  suitable  support,  and 


action  of  the  organisms  freely  abounding  in     warmed   very   gently   by    applying    heat    to 
the  debris  which  had  been  obtained  from  slates     the  under  surface,  a  considerable  movement 

EXPERIMENTS  ON  THE  BATE  OF  DESTRUCTION   OF   SOLID   MATTERS  IN  SLATE  BEDS,  PREPARED  WITH  DEPOSIT 
TAKEN  FROM  THE  SLATES  IN  THE  BEDS  AT  MALDEN,  SURREY. 


Substance. 

First  day,  after  20 
hours'  rest. 

Second  day. 

Third  day. 

Fourth  day. 

Fifth  day. 

Bread        

Zooglea   masses,  starch 

Numerous          bacteria, 

Bread  completely  disin- 



_ 

cells     spiral    vessels, 

starch  cells  very  at- 

tegrated, abundance  of 

motile  bacteria,  lepto- 

tenuated    and    losing 

leptothrix,    oscillaria, 

thrix,  green  confervse, 

form. 

monadina,clostriditim, 

&c.  Bread  undergoing 

quantity     of      round 

disintegration. 

granular  matter 

(?  worm  casts). 

Butter      

Mass  of  fat  cells    

Fat    cells    with   brown 

Brown  granular  matter 

Irregular  cellular  mem- 

Butter reduced  to  a 

granular  matter 

with    spirilla,    lepto- 

brane with  colonies  of 

tliin  wafer. 

(?  worm  casts). 

thrix,  fat  cells. 

micrococci  and  bacilli, 

&c. 

Cheese      

Masses  of  various 

Swarming  with  colonies 

Bundles  of  stellate  crys- 

Fat cells  crowded  with 

The  cheese  reduced 

bacteria,   i.e.,  bacilli, 

of  motile  bacilli. 

tals  interspersed  with 

bacilli  and  diplococci. 

to   a    thin    pasty 

micrococci,     strepto- 

numerous      bacteria, 

layer. 

cocci,  &c. 

motile  and  non-motile. 

Lettuce    

Chlorophyll     attacked, 
bacilli,        diplococci, 

Peaty   matter,    various 
bacteria. 

Granular  matter,  lepto- 
thrix, various  bacteria, 

Indefinite  debris  (?  worm 
casts)  ;  lettuce  decom- 

Last trace  of  lettuce 
disappeared. 

zooglea,      leptothrix. 

monadina,  amoeba,  in- 

posed to  granular  con- 

&c. 

fusoria,  &c. 

dition     almost      free 

from  bacteria  (?  action 

of  worms). 

Lean  pork 

Mud  black  underneath, 

Meat   in    fibrous  state, 

Muscular  fibre  extremely 

Muscular  fibre  entirely 

Pork  reduced   to  a 

(cooked) 

deep      chocolate     on 

muscular    fibres   em- 

attenuated, numerous 

destroyed,  the  residue 

thin  greyish  scum 

surface.,*  various  bac- 

bedded     in      zooglea 

spirilla,  motile  bacilli, 

being  alive  with  motile 

consisting  of  vari- 

teria, leptothrix,  and 

masses    of    bacteria, 

and    monadina,    zoo- 

bacilli, spirilla,  mona- 

ous organisms. 

encysted  infusoria. 

large      numbers      of 

glea,    oscillaria,   &c.  ; 

dina,     oscillaria,    an- 

*  ?  worm  casts. 

spirilla     and     motile 

the    whole   swarming 

guillute,  worms,  &c. 

bacilli,         anguillulas 

with  micrococci. 

and  worms. 

Tendon  from  roast 

Abundant      organisms, 

Enormous   numbers    of 

Swarming    with   micro- 

Quantity  of  brown 

Tendon  reduced  to  a 

pork  ;  very  hard 

vari  ous  bacteria 

micrococci  and  mona- 

cocci,   spirilla,   mona- 

granular    matter     (? 

soft  grey  mass. 

and  tough. 

single,  and  in  zooglea 

dina. 

dina,  granular  cellular 

worm  casts),    ingdil- 

form. 

matter  (?  worm  casts), 

lulse.worms,  monadina, 

fungoid  mycelium. 

many  bacteria,  zooglea 

masses,  oscillaria,  &c. 

Fat  of  ham 

Leptothrix,  strepto- 

Fat  cells    interspersed 

Fat  cells,  brown  granu- 

Fat  cells   with    zooglea 

Fat  largely  reduced 

cocci,  and   numerous 

with  various  bacteria. 

lar    matter    (?    worm 

masses,    spirilla,    &c., 

to    a    soft    pasty 

zooglea  masses. 

casts),  bacteria,  &c. 

various  infusoria,  opa- 

mass. 

lina,  oscillaria,  &c. 

Brewery  refuse  in 

Yeast   cells   practically 

All    odour   of   brewery 





— 

sewage. 

destroyed,  lepto- 

refuse      disappeared, 

thrix,  zooglea  masses, 

grey  surface  deposit. 

various  infusoria. 

in  actual  use.  The  examination  of  these  clearly 
indicates  that  the  process  of  destruction  of  the 
organic  matters  is  solely  due  to  the  result  of 
their  digestion  by  the  numerous  and  various 
organisms  present.  The  absence  of  offensive 
odour  and  the  ready  manner  in  which  the 
deposit  dries  to  a  powder  clearly  point  to  a 
vast  difference  between  this  matter  and  the 


will  soon  be  seen  to  take  place  on  the  imme- 
diate surface,  and  gradually  a  heaving  mass 
of  minute  worms  will  struggle  to  escape  from 
the  heated  underlayer.  These  are  clearly 
aerobic  organisms  whose  power  of  digestion  is 
considerable,  and  it  is  to  a  great  extent  their 
casts  which  form  the  inoffensive  humus  which 
escapes  from  the  slate  layers  with  the  effluent, 


438 


SLA 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


SLA 


thereby  preventing  the  accumulation  which  is 
the  cause  of  the  choking  of  the  old  coarse 
contact  beds. 

A  fragment  from  the  surface  of  the  deposit, 
collected  by  touching  it  with  the  point  of  a 
wire  and  placed  on  a  microscopic  glass  slide 
with  a  droplet  of  water,  covering  the  whole 
with  a  thin  glass  cover  in  the  usual  manner, 
may  be  examined  with  a  \  in.  or  higher  power. 
It  will  be  at  once  seen  to  be  largely  made  up 
of  innumerable  living  organisms  of  great 
complexity  and  variety,  other  than  the 
worms. 


digestion — the  waste  products  of  one  group 
being  but  food  for  a  lower. 

The  process  may  very  conveniently  be 
watched  from  day  to  day  by  placing  the 
previously  mentioned  small  piece  of  slate  in 
an  ordinary  plate  or  saucer,  and  putting  on 
the  "  living  earth  "  on  the  slate  small  frag- 
ments of  meat,  bread,  &c.,  and  flooding  the 
plate  with  water  gently  so  as  to  completely 
cover  the  whole.  After  an  hour  or  two  gently 
decant  the  water  from  the  plate  BO  as  to 
thoroughly  drain  the  plate  and  deposit  there- 
on. Leave  it  freely  exposed  to  the  air,  pre- 


EXPERIMENTS    WITH    DEPOSIT    COLLECTED   FROM    SLATES    IN    BED    TREATING    THE    SEWAGE    AT   A   PRIVATE    HOUSE. 

A  preliminary  microscopical  examination  showed  that  the  deposit  was  swarming  with  minute  red  worms,  anguillulse,  infusoria,  and  various 
bacteria. 


Substance. 

First  day. 

Second  day. 

Third  day. 

Fourth  day. 

Lean  of  raw  beef      
Cheese  

In   4   hours  the  red  colour 
had  turned  to  grey. 

In  4  hours   the  cheese  was 

The  beef  had  sunk  into  the 
mud,  grey  in  colour,  and 
swarming  with  bacilli, 
spirilla,  monadina,  &c. 

Beef  scarcely  visible,  being 
now  one  mass  of  various 
organisms. 

Meat  entirely  disappeared. 

light  grey  in  colour. 

swarming  with  bacilli  of 
various  kinds. 

layer. 

pasty  condition. 

On  November  2nd,  1908,  7  grammes  of  raw  liver  were  placed  on  a  layer  of  the  above  deposit,  laid  on  the  bottom  of  a  4in.  Petri  dish,  the 
area  being  12  in.  approximately.    The  quantity  of  liver  thus  treated  was  equal  to  the  treatment  of  a  sewage  100  times  normal  strength. 


First  day  (after 
24  hours). 

Second  day. 

Third  day. 

Fourth  day. 

Eighth  day. 

Fifteenth  day. 

Liver  had  lost  colour, 
odour  unpleasant. 

Odour  offensive. 

Very  offensive. 

Odour  decidedly 
reduced. 

Odour  had  en- 
tirely disap- 
peared. 

Liver  reduced  to  a  very  few  resistant  pieces, 
which  were  covered  with  whitish  grey  spots 
consisting  of  bacillus  -megatherium.  Later, 
a  growth  of  the  mould,  mucor  caninus, 
developed. 

NOTE.— This  experiment  was  very  drastic.  The  liver  was  laid  very  thickly,  with  scarcely  any  room  between  the  pieces,  none  of  which  was 
smaller  than  ^in.  diameter,  whilst  many  approached  iin. 

On  November  6th  another  dish  was  similarly  charged  with  1  gramme  of  beef  steak  raw,  1  gramme  of  beef  fat,  and  1  gramme  of  cheese.  On 
the  sixth  day  the  cheese  had  entirely  disappeared,  the  beefsteak  was  reduced  to  a  greyish  soft  mass,  and  the  fat  was  disintegrated. 


From  these  simple  examinations  it  will  be 
evident  that  instead  of  an  inert  mass  of  matter 
we  have  a  hive  of  active  and  voracious  living 
organisms,  from  the  lowest  type  of  bacteria 
up  to  the  highly  organised  worms,  larvse,  &c., 
which,  like  a  collection  of  animals  in  a  zoolo- 
gical gardens,  feed  upon  the  daily  supply  of 
food  given  to  them,  and  so  long  as  this  supply 
is  steadily  and  regularly  maintained,  so  long 
will  they  perform  their  life  functions,  and  in 
so  doing  destroy  the  waste  organic  matters 
which,  in  their  collective  form,  we  call  sludge ; 
the  process  involved  being  merely  that  of 


ferably  in  a  moderately  warm  atmosphere. 
On  watching  from  time  to  time  it  will  be  seen 
that  the  piece  of  red  meat  has  become  coated 
with  a  grey  deposit,  this  being  often  complete 
in  4  or  5  hours.  Now  touch  the  grey 
matter  with  the  point  of  a  wire,  and  transfer 
the  minute  quantity  thus  taken  up  to  a  micro- 
scope slide  as  before,  and  examine  under  a 
high  power,  when  it  will  be  seen  that  this 
grey  matter  is  nothing  but  an  enormous  num- 
ber of  bacteria,  many  in  a  state  of  restless 
activity  where  they  are  not  crowded  in  zooglea 
masses  which  prevent  their  rapid  movements. 


439 


SLO 


ENCYCLOPAEDIA   OF 


SLU 


Continue  these  observations  from  day  to 
day,  each  day  flooding  with  water  and  draining 
after  2  hours  or  so.  In  a  few  days  the  solid 
particles  of  meat,  &c.,  will  become  invisible 
and  merged  in  the  mass  of  black  humus  into 
which  it  is  finally  resolved. 

It  is  evident  that  this  is  precisely  what  takes 
place  in  a  slate  bed.  "When  the  bed  is  first 
filled  with  sewage,  and  allowed  to  stand  full 
in  a  quiescent  state  for  a  couple  of  hours,  the 
solid  matters  settle  on  the  slates.  Until  the 
"  living  earth  "  is  fully  developed,  the  destruc- 
tive action  is  slow,  but  in  warm  weather 
especially  the  organisms  rapidly  develop  and 
attack  the  food  thus  provided  for  them, 
exactly  as  the  organisms  in  a  river  mud  attack 
the  matter  deposited  thereon  from  a  tidal 
water  receiving  sewage  matters,  and  if  the 
ratio  of  organisms,  food  and  air  supply  are 
properly  regulated,  the  action  proceeds  in- 
definitely without  the  evolution  of  nauseous 
odours. 

The  account  given  in  the  tables  of  a  series 
of  experiments  made  to  ascertain  the  rate  of 
destruction  of  various  food-stuffs  when  placed 
on  the  mud  on  the  slates  will  be  of  interest. 

W.  J.  D. 

Slop  Hoppers. — Provided  in  many  houses 
for  the  reception  of  bedroom  slops  and  other 
fouled  liquids.  They  must  be  treated  in  every 
way  as  water-closets,  which  fittings  the  most 
cleanly  slop  sinks  resemble  in  shape.  Like 
water-closets,  these  hoppers  must  be  provided 
with  flushing  rims,  and  should  be  flushed  by 
water  waste-preventing  cisterns.  Unlike 
closets,  however,  they  should  be  fitted  with 
a  loose  grating  over  their  outlets,  in  order  to 
intercept  pieces  of  soap,  scrubbing  brushes, 
cloths,  and  similar  articles  which  may  be 
carelessly  thrown  in  with  the  slops.  The 
height  of  their  upper  edge  in  front  should 
not  exceed  1  ft.  6  in.  from  the  floor,  in  order 
that  pails  may  be  conveniently  emptied  out. 
The  higher  a  pail  has  to  be  lifted  the  greater 
is  the  probability  of  the  surroundings  being 
splashed.  Where  space  is  available,  it  is  both 
desirable  and  a  convenience  to  fix  a  wash-up 


sink  in  connection  with  the  slop  sink,  for  the 
purpose  of  rinsing  the  emptied  out  receptacles 
and  for  refilling  bedroom  jugs.  The  waste  of 
this  sink  may  be  conveniently  arranged  to 
discharge  into  the  slop  hopper,  and  need  not 
be  trapped.  Various  manufacturers  make 
fittings  in  which  these  two  forms  of  sinks  are 
combined  and  made  in  one  piece.  These,  as 
a  rule,  are  of  good  design,  and  preferable  to 
two  separate  appliances. 

Sludge  (from  precipitated  sewage).— 

The  weight  of  wet  sewage  sludge  produced 
per  million  gallons  of  sewage  varies  consider- 
ably in  different  places.  At  Manchester  it  is 
mentioned  as  21  tons,  Salford  and  London 
about  26  tons,  Chorley  60  tons.  About  40 
tons  per  million  gallons,  when  containing 
about  90%  of  moisture,  is  perhaps  an 
average  amount,  but  in  comparing  weights 
the  percentage  of  moisture  must  be  taken  into 
account.  The  reduction  in  weight  at  varying 
degrees  of  dryness  is  readily  calculated  by  the 
following  rule  :— 

100  -  P 

y- 


100  —  Q 
In  which — 

x  =  weight  of  sludge  cake  produced. 

)/  =  original  weight  of  the  wet  sludge. 

P  =  percentage  of  moisture  in  the  wet 
sludge. 

Q  =  percentage  of  moisture  after  pressing. 
A  cubic  yard  of  wet  sludge  weighs  about 
16  cwt.,  and  a  cubic  yard  of  broken  cake  as 
delivered  from  a  filter-press  weighs  12  cwt. 
Ordinary  precipitated  sludge  commonly  con- 
tains about  95%  of  moisture,  and  septic 
sludge  90%.  The  quantity  of  wet  sludge 
produced  varies  according  to  the  sewage 
and  the  chemicals  used,  but  the  average 
quantity  yielded  daily  per  1,000  persons  in 
eight  towns  where  lime  and  sulphate  of 
alumina  were  added  to  the  sewage  was  '92 
tons.  In  dealing  with  sludge  it  is  important 
to  remember  that  a  small  reduction  in  per- 
centage of  moisture  means  a  very  marked 
reduction  in  bulk  and  weight,  hence,  also, 
in  cost  of  disposal.  For  example,  100  tons 


440 


SLU 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


SLIT 


of  sludge  containing  95%  of  moisture 
equals  50  tons  only  when  the  moisture  is 
reduced  to  90%,  as  will  be  apparent  from 
the  above  rule.  Sewage  sludge  is  of  low 
manurial  value,  and  contains  only  small 
quantities  of  nitrogenous  compounds  and 
phosphates,  with  a  large  amount  of  mineral 
matter,  water,  and  some  cellulose.  Its  dis- 
posal constitutes  one  of  the  chief  difficulties 
in  sewage  treatment.  Some  of  the  means 
adopted  are :  Manufacture  into  marketable 
manure,  depositing  at  sea  in  deep  water, 
pressing  into  sludge  cake  and  disposal  on 
land,  running  of  liquid  sludge  into  trenches 
and  burying  on  land,  air-drying  on  the  surface 
of  land  or  in  lagoons,  and  then  digging  or 
ploughing  into  land,  burning  of  sludge  in 
destructors,  and  extracting  marketable  con- 
stituents for  sale.  At  Kingston-on-Thames 
the  precipitation  of  the  sewage  and  disposal  of 
the  sludge  costs  Is.  8d.  per  head  of  the  popu- 
lation per  annum,  and  the  sludge  is  made 
into  a  marketable  "  native  guano."  At  Dal- 
marnock,  Glasgow,  the  sludge  is  produced  by 
precipitation  with  lime  and  ferric  sulphate, 
and  part  is  sold  in  the  form  of  pressed  cake 
at  8d.  to  Is.  per  ton  in  bulk  at  the  works,  and 
a  part  is  made  into  a  manure  ("  Globe  Ferti- 
liser "),  and  sold  at  from  8s.  to  10s.  per  ton  in 
bulk.  The  cost  of  pressing  the  "  cake  "  is  2s. 
per  ton,  and  of  the  production  of  the  "  fertiliser" 
about  10s.  per  ton.  For  towns  on  the  sea- 
board the  disposal  of  sludge  by  depositing  in 
deep  water  is  usually  the  cheapest  plan  in  the 
circumstances.  The  London  sludge  is  deposited 
at  the  Barrow  Deep  20  miles  below  Southend, 
the  Glasgow  (Dalmuir)  sludge  at  a  point  three 
miles  below  "  Garroch  head,"  40  miles  from 
Glasgow,  and  that  from  Manchester  (Davy- 
hulme  Works)  through  the  Ship  Canal,  and 
dumped  in  deep  water  outside  the  north-west 
lightship.  Other  towns  disposing  of  sludge 
by  sea  are  Salford,  Dublin,  and  Southampton. 
The  total  cost,  including  interest  and  sinking 
fund,  of  this  mode  of  disposal  of  sludge  con- 
taining 90%  of  water  ranges  from  about 
4d.  to  Id.  per  ton,  according  to  local  con- 
ditions. The  pressing  of  sewage  sludge, 


though  not  a  means  of  final  disposal,  greatly 
facilitates  the  subsequent  handling  of  the 
material,  and  puts  it  into  a  form  which  makes 
its  cartage  or  sale  to  farmers  and  others 
possible.  The  moisture  in  pressed  sludge- 
cake  is  reduced  to  from  65  to  50%.  The 
precipitated  sludge  from  settling  tanks  is 
swept  out  into  a  sludge  well  and  the  super- 
natant liquor  drawn  off.  The  thick  sludge 
remaining  is  mixed  with  -5  to  1  %  of  lime, 
and  then  forced  by  compressed  air  into 
the  filter  presses,  where  some  30  to  35  % 
of  the  sludge  water  is  pressed  out.  The 
"cake"  falls  from  the  press  into  trucks, 
and  is  sold  or  given  away  to  farmers, 
tipped  at  some  available  shoot  or  buried.  If 
tipped  on  land  in  bulk  it  should  be  covered 
with  a  layer  of  earth,  and  sown  with  seed  or 
turfed  to  avoid  smells.  At  York  uneven  land 
is  being  levelled  in  this  way.  Sludge  pressing 
is  carried  on  at  a  number  of  towns,  including 
Burnley,  Chorley,  Baling,  Hanley,  Ley  ton, 
Nelson,  Wolverhampton,  Wimbledon,  and 
Willesden.  The  cost  of  pressing  per  ton  of 
pressed  cake  varies  from  Is.  6d.  to  4s.  Qd., 
about  2s.  per  ton  being  a  very  common 
figure,  exclusive  of  interest  and  sinking  fund 
on  cost  of  plant.  At  Birmingham,  Guildford, 
and  Withington  the  precipitated  sludge  is  run 
into  Y-shaped  trenches  on  land,  and  after 
covering  with  earth  and  allowing  time  to  dry, 
is  then  ploughed  in  and  the  land  cropped. 
Care  is  necessary  to  avoid  nuisance,  especially 
with  septic  sludge.  About  1  acre  of  medium 
quality  of  land  would  probably  be  required  to 
deal  with  1,000  tons  of  wet  sludge  per  year. 
The  cost  of  this  method  of  disposal  varies 
from  4d.  to  Id.  per  ton  of  wet  sludge.  At 
Baling,  Leyton,  and  Huddersfield  sewage 
sludge  is  mixed  with  house  refuse,  in  the 
proportion  of  one  of  sludge  to  about  two  of 
refuse,  and  burnt  in  refuse  destructors.  At 
Huddersfield  coke  breeze  is  substituted  when 
refuse  is  not  available.  The  cost  of  burning 
the  sludge  amounts  to  2s.  to  2s.  6d.  per  ton. 
At  Bradford,  where  the  sewage  contains  a 
large  proportion  of  wool-scouring  liquor,  the 
fat  is  extracted  and  sold  at  a  profit.  In 


441 


3MO 


ENCYCLOPAEDIA   OF 


SMO 


Watson  and  Butterfield's  patent  sludge  dis- 
tilling process  the  object  is  to  recover  the 
nitrogen  from  the  sludge  in  the  form  of 
ammonia,  and  to  use  the  carbonaceous  matter 
for  generating  heat.  The  manurial  value  of 
sludge  on  land  is  not  great,  it  is  slow  in  acting 
and  does  not  appear  to  be  very  suitable  for 
root  crops.  W.  H.  M. 

Smoke  Prevention. — Smoke  may  result 
from  the  combustion  of  a  variety  of  fuels,  and 
in  several  processes  of  manufacture ;  but  the 
remarks  which  follow  refer  particularly  to 
that  from  ordinary  bituminous  coal.  Coal 
smoke  is  made  up  of  particles  of  unburnt 
carbon,  ash,  and  condensed  tarry  vapours  and 
steam,  suspended  in  the  gases  issuing  from 
the  fire.  It  is  an  indication  of  imperfect  com- 
bustion. To  deal  intelligently  with  the  problem 
of  prevention  we  must  understand  the  causes 
of  its  formation.  Briefly  then  smoke  is  formed 
as  follows  : — When  bituminous  coal  is  placed 
on  a  fire  it  first  undergoes  distillation,  and 
the  familiar  yellow  smoke,  composed  of  con- 
densed tarry  vapours,  is  given  off.  Soon  these 
vapours  and  the  accompanying  gases  take  fire, 
and  burn  with  a  bright  flame ;  it  is  from  this 
flame  that  the  carbon  particles  of  the  smoke 
come.  The  flaming  matter  consists  of  hydro- 
carbons, the  chief  of  which  are  Methane  or 
marsh  gas — CH4,  Ethylene  or  olefiant  gas — 
C2H4,  and  Acetylene — C2H2.  If  combustion  is 
perfect  these  burn  to  carbon  dioxide  and  water, 
thus — 

CH4  +  40  =  C02  +  2H20. 
If  insufficient  oxygen  is  available  this   may 
become— 

CH4  +  20  =  C  +  2H20, 
the  result  being  soot  and  water  ;  and  if  the 
heat  is  sufficient  to  split  up  the  hydrocarbons, 
but  no  oxygen  is  supplied,  they  may  simply 
dissociate  into  carbon,  or  soot,  and  hydrogen 
thus — 

CH4  =  C  +  H4. 

Marsh  gas  is  taken  in  these  formulae,  but  the 
other  hydrocarbons  produce  the  same  sub- 
stances. Probably  the  soot  in  coal  smoke  is 


produced  in  this  way.  The  maximum  amount 
of  soot  is  therefore  limited  by  the  amount  of 
volatile  carbon  in  the  coal,  30%  of  which  is 
about  an  average.  The  amount  of  fuel  lost  in 
soot,  however,  probably  seldom  exceeds  £%  of 
that  burnt.  The  formation  of  soot  means  that 
unburnt  gases  are  escaping,  and  these  may 
cause  serious  loss.  The  intensity  of  smoke  has 
usually  been  measured  by  comparison  with 
charts  or  cards  having  numbered  and  gradu- 
ated shades  printed  on  them.  The  best  known 
of  these  is  Eingleman's,  which  has  five  such 
shades,  made  by  ruling  black  lines  of  different 
thicknesses  at  right  angles  to  each  other  on 
white  cards.  The  shades  are  obtained  as 
follows  : — 

No.  1  has  black  lines  1  mm.  thick  and  9  mm.  apart. 
.,    2         „         „         2-3     „         „         7-7 
„    3         „         „         3-7     „         „          6-3 

A  K.K  A-K 

»        -  )»  »  <J   «         J)  »  », 

,,    5  is  all  black. 

The  cards  should  be  about  9  in.  square, 
and  placed  about  50  or  60  ft.  from  the  eye, 
and  compared  with  the  smoke  issuing  from 
the  chimney  ;  the  lines  and  spaces  give  at 
this  distance  a  grey  effect.  Such  a  method  is 
crude,  and,  except  for  comparing  the  smoke 
from  the  same  chimney  at  different  times,  or 
from  chimneys  of  similar  diameter,  is  of 
little  use.  The  shade  of  the  smoke  depends 
as  much  on  the  thickness  of  the  layer  looked 
through  as  on  its  density.  Any  such  method 
should,  to  be  at  all  accurate,  take  account  of 
the  diameter  of  the  chimney.  The  advisability 
of  preventing  smoke  arises,  not  only  from  the 
loss  of  fuel  involved  in  its  production,  as  from 
its  injurious  effects  on  animal  and  vegetable 
life,  as  well  as  on  buildings.  Few  plants 
thrive  in  smoky  cities,  the  air  of  which  is 
especially  fatal  to  conifers  ;  the  plane  tree  is 
one  of  the  few  that  can  survive  such  con- 
ditions. The  effect  of  smoke  on  buildings  is 
due  to  the  deposit  of  its  solid  matter,  which 
not  only  disfigures  them  but  acts  as  a  vehicle 
for  the  sulphur  acids  evolved  with  the  smoke; 
these  attack  limestone  and  iron-work,  and 
rapidly  destroy  them. 

Turning   now  to   methods   of   prevention : 


442 


SMO 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


SMO 


certain  primary  conditions  must  be  fulfilled  ; 
these  are : — 

(1)  Enough  air  must  be  supplied  to  com- 
bine with  the  carbon  of  the  fuel. 

(2)  This  air  must  be  mixed  intimately  with 
the  gases  from  the  coal. 

(3)  The  temperature  of  the  gases  must  not 
fall  below  700°  C.  until  combustion  is  com- 
pleted. 

The  undue  cooling  of  the  gases  is  probably 
the  most  potent  cause  of  smoke,  as  it  is  more 
common  to  have  too  much  air  supplied  than 
too  little,  and  this  reduces  the  temperature  of 
the  gases  below  the  ignition  point.  Such  cooling 
also  results  from  the  contact  of  flame  with  a 
cold  surface,  such  as  that  of  water-tubes  or 
boiler-plates  ;  hence  it  is  important  to  provide 
in  boiler  furnaces  a  sufficient  space  for  com- 
bustion to  be  completed  before  the  flames 
come  in  contact  with  the  comparatively  cold 
surface  of  the  boiler.  This  means  the  pro- 
vision of  a  sufficiently  large  fire-brick-lined 
combustion  chamber. 

When  we  consider  domestic  fires,  which  are 
a  source  of  a  large  proportion  of  smoke,  we 
see  that  it  is  practically  impossible  to  fulfil 
the  above  conditions.  Too  much  air  is 
admitted,  the  gases  are  cooled  below  their 
ignition  points,  and  the  flames  come  in  con- 
tact with  cold  surfaces  at  many  points.  We 
may  say,  therefore,  that  no  method  has  ever 
been  devised  which  prevents  the  issue  of 
smoke  from  domestic  grates  burning  bitumin- 
ous coal.  The  solution  of  the  smoke  problem 
lies  in  a  different  direction,  and  will  doubtless 
be  the  burning  of  a  smokeless  fuel,  either 
solid  or  gaseous.  Of  solid  we  have  a  choice 
of  anthracite,  coke,  or  partially  coked  coal ; 
and  of  gaseous  we  have  at  present  only  coal- 
gas  to  consider.  In  a  country  where  electricity 
can  only  be  produced  on  a  large  scale  by  the 
combustion  of  coal  we  can  hardly  look  to 
electric  heating  as  a  solution,  owing  to  its 
cost.  Domestic  heating  by  means  of  ordinary 
coal  or  coke  fires,  anthracite  burnt  in  specially 
constructed  stoves,  and  gas  fires,  when  the 
fires  are  run  continuously,  costs  approximately 
as  follows,  based  on  tests  in  rooms  of  about 


4,000  cub.  ft.  capacity  :— Coal  0'026  to  0-033, 
coke  0'037,  anthracite  O'Ol,  and  coal  gas  O'll, 
in  pence  per  hour  per  degree  F.  of  rise  in 
temperature  of  the  room  air. 

It  is  probable  that  the  solution  of  smokeless 
domestic  heating  will  be  eventually  found  in 
the  production  of  some  form  of  cheap  gas  at 
the  coalfields,  and  its  supply  to  our  cities 
through  high-pressure  mains. 

The  case  of  large  furnaces  for  steam  raising 
is  different,  and  these  can  be  successfully 
operated  with  bituminous  coal  with  a  practical 
absence  of  smoke.  It  is  chiefly  a  question  of 
stoking,  but  the  furnaces  must  be  properly 
constructed  and  proportioned  in  the  first 
instance,  with  ample  grate  area  and  com- 
bustion chamber.  It  has  been  found  that 
while  theoretically  hand  stoking  can  be  so 
done  as  to  practically  prevent  smoke,  too 
much  depends  on  the  stoker,  and  mechanical 
appliances  are  more  successful. 

Mechanical  stokers  may  be  roughly  divided 
into  three  classes  : — 

(1)  Coking  stokers.     In  'these  the  coal  is 
fed   mechanically   to   the   front  part  of   the 
furnace,    where   the   gases   are  distilled   off; 
these  are  passed  over  the  incandescent  fuel  at 
the  back,  and  there  burnt.     As  the  gases  are 
driven  off,  the  coke  left  is  pushed  gradually 
towards  the   back  of  the  furnace  and  there 
burnt. 

(2)  Sprinkling  stokers.     These  act  by  scat- 
tering  over   the    incandescent    fuel    in    the 
furnace   small    quantities   of    fresh    coal   at 
regular  intervals.     The  quantity  being  small 
is  consumed  with  little  or  no  smoke. 

(3)  Underfeed    stokers.     In    this   type   the 
fuel  is  forced  up  from  below  at  a  regular  rate 
into    a   specially   constructed   furnace.     The 
gases  distilled  off  are  therefore  forced  to  pass 
up   through    the    incandescent    fuel    on    the 
surface,  and  are  thus  consumed. 

Smoke  may  be  prevented  also  by  forcing 
jets  of  heated  air  into  the  furnace  near  the 
back. 

Turning  now  to  the  legal  aspect  of  the 
question.  The  Public  Health  Act  of  1875 
contains  the  statutory  law  relating  to  smoke 


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ENCYCLOPEDIA   OF 


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emission  throughout  England,  excepting 
London. 

The  Public  Health  Act  (London)  of  1891 
includes  the  sections  relating  to  smoke  in  the 
Act  of  1875,  making  them  applicable  to  the 
administrative  county  of  London. 

Both  of  these  Acts  make  it  an  offence  to 
emit  from  any  chimney,  not  being  the 
chimney  of  a  private  dwelling-house,  "  black 
smoke  in  such  quantities  as  to  be  a 
nuisance." 

It  is  curious  to  observe  that  there  is  prob- 
ably no  such  thing  as  "  black  "  coal  smoke ; 
it  is  usually  of  a  brownish  shade,  hence  the 
presence  of  the  word  black  renders  the  appli- 
cation of  the  Act  difficult.  J.  8.  0. 

Snow. — When  the  temperature  of  the  air 
is  about  or  below  the  freezing-point,  precipita- 
tion usually  takes  the  form  of  snow  instead  of 
rain.  Snow-flakes  are  six-pointed  crystals, 
and  are  of  great  variety.  Scoresby,  Glaisher, 
and  others  have  made  a  large  number  of 
drawings  of  snow  crystals ;  and  during  recent 
years  photographs  of  snow-flakes  under  the 
microscope  have  been  obtained,  notably  by 
Mr.  W.  A.  Bentley,  of  Jericho,  Vt.,  U.  S.  A. 
These  all  show  the  crystals  to  be  of  extreme 
beauty.  When  snow  is  falling,  if  any  one 
will  catch  some  of  the  flakes  on  the  sleeve 
of  his  coat  and  look  at  them  under  a  mag- 
nifying glass,  he  will  be  charmed  by  their 
exquisite  beauty.  Their  size  varies,  but  it  is 
generally  from  one-tenth  to  three-tenths  of 
an  inch  in  diameter.  Although  snowflakes 
are  so  small,  yet  when  they  accumulate  they 
often  do  a  great  deal  of  damage,  especially  if 
the  wind  is  high  and  causes  snow-drifts. 
These  render  traffic  almost  impossible,  and 
often  cause  loss  of  life  to  both  human  beings 
and  animals.  Snow  is  measured  by  the  rain- 
gauge  ;  that  which  is  collected  in  the  funnel 
being  melted  and  measured  as  rain.  A  foot 
of  snow  is  roughly  equal  to  an  inch  of  rain. 
Snow,  however,  varies  greatly  in  density ; 
with  very  loose  snow  as  much  as  16  in. 
may  only  produce  an  inch  of  water,  while  at 
other  times,  especially  in  blizzards,  snow  may 


be  granular,  something  like  sand,  and  then 
7  in.  may  produce  an  inch  of  water.        W.  M. 

Soil  Pipes.     (See  "PLUMBING.") 

Sol. — A  term  introduced  by  Graham  to 
denote  the  apparent  solubility  of  colloidal 
matters  (q.  v.). 

Sparge  Pipe. — A  pipe  having  fine  holes 
drilled  throughout  its  length  so  as  to  deliver 
a  spray  of  water  as  is  required  for  flushing. 

Spence's  "Alumino  Ferric"  (Treat- 
ment of  Sewage). — Alumino-ferric  and  lime 
are  used  as  precipitants  at  Chiswick,  on  the 
advice  of  Dr.  Tidy,  chemist.  Seven  grains  of 
lime  to  the  gallon  and  five  grains  of  the  alum 
in  solution  are  incorporated  with  the  sewage 
by  agitation.  After  precipitation  the  tank 
effluent  is  filtered.  To  each  hundredweight 
of  wet  sludge  are  added  14  Ibs.  of  lime  pre- 
vious to  pressing  in  filter  presses.  The  sludge 
is  burned  in  a  "  Horsfall "  refuse  destructor. 

Sprinklers  for  Sewage  Beds.  (See 
"SEWAGE  DISPOSAL"  and  " DISTRIBUTORS,  FOR 
SEWAGE.") 

Springs. — These  are  of  two  classes,  "  Land 
Springs"  and  "Deep  Springs."  The  land 
springs  rise  from  superficial  beds  of  sand  or 
gravel  lying  upon  an  impermeable  stratum  of 
clay  or  rock ;  consequently  their  flow  is 
irregular,  are  immediately  dependent  on  the 
rainfall,  and  are  generally  dry  during  summer. 
Deep  springs  are  supplied  from  deep-seated 
water-bearing  stratum,  such  as  chalk,  green- 
sand,  &c.  The  water  therefrom  is  usually 
free  from  organic  and  suspended  matters, 
having  filtered  through  considerable  thick- 
nesses of  strata.  Spring-water  often  contains 
dissolved  inorganic  matters  taken  up  from  the 
rocks  through  which  it  has  percolated.  The 
flow  or  yield  of  a  deep  spring,  though  variable, 
is  more  constant  than  that  of  land  springs, 
and,  generally  speaking,  the  deeper  the 
stratum  from  which  the  supply  is  obtained, 
'  the  more  regular  the  flow.  Very  commonly 
the  yield  is  lowest  in  October  or  November, 


444 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


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and   highest   in   the   following   February   or 
March,  but  is  dependent  upon  the  rainfall. 

Various  conditions  determine  the  amount  of 
rain  which  percolates  the  ground :  (1)  nature 
of  the  soil ;  (2)  configuration  of  the  land ; 
(3)  temperature  and  movement  of  the  air. 
Clay  is  almost  impervious,  gravel  or  a  loose 
sandy  soil  absorb  about  96%,  limestone 
about  20%,  chalk  about  42%.  In  a  flat 
district  evaporation  may  amount  to  50  %  less 
than  in  an  undulating  one.  "  Land  "  springs 
are  derived  from  shallow  beds  of  gravel,  and 
their  flow  is  uncertain.  "  Main  springs " 
come  from  deeper  strata ;  their  yield  is  more 
constant,  and  usually  of  a  better  quality. 
Where  springs  afford  the  supply  to  a  town, 
the  "  gathering  grounds "  require  to  be 
kept  under  close  observation  to  detect  any 
possible  sources  of  pollution.  As  instances 
of  good  supplies  from  springs  may  be  men- 
tioned the  chalk-water  springs  of  Amwell 
and  Chadwell  in  Hertfordshire,  the  supplies 
to  Malvern  and  Tunbridge  Wells.  Some  of  the 
best  spring  waters  are  derived  from  granitic, 
Jurassic  and  cretaceous  strata.  Spring  and  deep 
well  waters  form  a  favourable  medium  for  the 
propagation  of  certain  germs,  and  should, 
therefore,  be  carefully  guarded  against  pollu- 
tion in  the  course  of  delivery  to  the  consumer. 

Stable  Construction  and  Sanitation.— 

The  essential  conditions  in  stable  construc- 
tion from  a  sanitary  standpoint,  as  distinct 
from  the  architectural,  are  : — Lighting,  venti- 
lation, paving,  and  drainage.  Ample  light 
makes  for  health  and  cleanliness,  and,  as 
glass  is  cheap,  windows  and  skylights  may  be 
freely  used  if  so  placed  and  arranged  as  not 
to  create  draughts.  Where  economy  is  a 
consideration  the  admission  of  light  may  be 
arranged  for  by  the  insertion  of  squares  of 
rough  plate-glass  or  of  glass  tiles  in  the  roof. 
As  regards  ventilation,  this  is  amply  provided 
for  during  the  day  by  the  windows  and  doors, 
which  latter  it  is  usual  to  hang  in  halves,  so 
that  the  upper  half  may  be  left  open  wrhile 
the  lower  is  closed.  It  is  during  the  night 
and  at  other  times  at  which  stables  are  closed 


that  ventilation  must  be  chiefly  arranged  for. 
This  is  best  done  by  inlets  fixed  under  the 
mangers  and  louvred  outlets  in  the  roof,  or 
near  the  ceilings  where  there  are  rooms  above 
the  stables.  Stable  paving  must  in  all  cases 
be  impervious,  and  may  consist  of  grooved 
bricks  made  for  the  purpose,  or  of  blue  bricks 
on  edge  grouted  in  cement,  or  of  concrete, 
granolithic  cement,  and  similar  materials.  It 
is  desirable  that  such  surfaces  be  provided 
with  shallow  channelling,  on  the  one  hand,  to 
facilitate  the  draining  away  of  moisture,  and, 
on  the  other,  to  prevent  horses  or  other 
animals  from  slipping.  The  floors  should  be 
laid  to  a  slight  fall  towards  a  collecting 
channel  or  gulley  in  the  centre  or  at  the  back 
of  each  stall,  the  latter  being  the  more  desir- 
able. This  fall  should  not  exceed  1  in  40, 
as  a  steeper  inclination  causes  discomfort  to 
animals.  The  gradient  named  is  quite  suffi- 
cient for  the  object  in  view,  if  the  floor  is 
reasonably  well  laid.  The  collecting  channels 
may  be  formed  in  the  flooring  itself  with 
cement  or  blue  bricks,  &c.,  or  they  may  take 
the  form  of  cast-iron  stable  channelling  having 
longitudinal  slits  in  the  cover  which,  while 
admitting  liquids  to  the  channels  below,  will 
exclude  from  them  straw  or  other  bedding 
materials.  These  covers  should  be  removable 
in  order  that  the  channels  may  be  occasion- 
ally swilled  with  water  and  brushed  out. 
The  channels  should  be  carried  through  the 
wall  to  the  exterior  and  arranged  to  discharge 
over  gully  traps,  which  in  their  turn  may  be 
connected  to  the  general  drainage  scheme,  or 
arranged  to  discharge  into  a  properly-con- 
structed tank  in  cases  where  it  is  desired  to 
collect  the  liquid  for  manurial  purposes. 
Channels  in  stables  are  preferable  to  collecting 
gullies,  as  the  drains  from  these  are  not  so 
readily  kept  clean  as  the  channels.  If  used, 
the  gullies  should  be  provided  with  double 
gratings  to  exclude  straw,  &c.,  from  the 
drains.  The  drains  from  them  should  also 
be  arranged  to  discharge  over  gullies  in  the 
open,  as  the  seals  of  the  traps  in  the  stables 
are  liable  to  be  destroyed  by  evaporation.  As 
regards  the  walls,  partitions,  and  the  general 


445 


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ENCYCLOPEDIA   OF 


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construction  of  stables,  it  may  be  said  that  all 
should  be  as  smooth  as  possible  so  as  to 
minimise  possible  lodgment  for  dust,  dirt,  and 
bacteria.  For  the  same  reason  all  angles  and 
corners  should  be  rounded.  The  walls  and 
partitions  should  further  be  so  constructed 
and  decorated  that  they  may  be  easily  washed 
down.  G.  J.  G.  J. 

Stand-pipes.  (See  "  WATEK  SUPPLY  "  and 
"  PUMPS  AND  PUMPING  MACHINERY.") 

Stand-pipe  and  Air-Vessel. — These  are 
important  accessories  in  connection  with  any 
system  of  pumping  machinery,  their  function 
being  to  absorb  the  excess  and  to  compensate 


—Water 


FIG.  1. — Cylindrical  Air-vessel  on  Delivery  Main. 

for  the  deficiency  of  delivery  by  the  pumps. 
Excess  of  delivery  causes  the  water  column 
in  the  stand-pipe  to  rise,  and  this  falls  again 
when  needed  to  balance  any  deficiency  of 
supply.  The  work  thus  expended  in  lifting 
the  water  column,  or  of  forcing  water  into  the 
air-vessel  against  the  cushion  of  compressed 
air  contained  in  the  upper  part  of  the  dome, 
is  given  out  again  to  the  advancing  water  in 
the  main  and  so  equalises  any  weakness  of 
pressure  occurring  therein. 

The  air-vessel  also  relieves  the  valves  from 
severe  shocks,  and  is  of  special  use  on  high 
lifts  and  heavy  pressures.  Air  vessels  often 
enable  pumps  to  be  worked  at  increased 
speeds,  and  should  be  so  arranged  as  to  be 
readily  recharged  with  air  to  replace  absorption 
by  the  water. 

In  considering  the  size  and  shape  of   an 


air-vessel  the  degree  of  pressure  and  the  ratio 
of  excess  of  delivery  of  the  pumps  are  the 
important  factors  to  be  kept  in  view.  In 
practice  the  sizes  vary,  according  to  circum- 
stances, from  four  to  fourteen  times,  or  more, 
the  capacity  of  the  barrel  of  the  pump.  Air- 
vessels  are  made  proportionately  larger  when 
subjected  to  high  pressures.  To  prevent  the 


Reservoir 


Stand-pipe 
FIG.  2. — Three-legged  Stand-pipe  on  Pumping  Main 

water  being  forced  too  high  into  the  air-vessel 
and  the  rapid  absorption  of  the  air  by  the 
water,  the  vessel  is  usually  made  with  a  long 
narrow  neck,  as  the  larger  the  surface  in  con- 
tact with  the  water  the  quicker  the  absorption. 
Sometimes  a  disc  of  wood  an  inch  or  two 
smaller  than  the  diameter  of  the  air-vessel  is 
placed  on  the  top  of  the  water  in  the  vessel  so 


\ReUef-pipe 


-Stand- pipe 


\DeliveryMiin 
FlG.  3. — Elevation  of  Stand-pipe  on  Pumping  Main. 

as  to  reduce  the  surface  in  contact  with  the 
air.  Provision  must  be  made  by  means  of  a 
small  air-pump,  or  by  a  "  snifting-valve,"  for 
replenishing  the  air  in  the  vessel  thus  gradu- 
ally dissolved  in  the  water.  An  air-vessel,  to 
be  most  effective  in  the  prevention  of  shocks 
due  to  the  momentum  of  the  water  in  the 
opening  and  closing  of  the  valves,  should  be 
placed  close  to  the  pump  on  the  delivery 


446 


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MUNICIPAL   AND    SANITAKY  ENGINEEEING. 


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main  and  connected  up  by  a  branch  pipe  of 
large  diameter.  Where  a  large  mass  of 
water  is  put  into  motion  in  the  suction-pipe 
by  each  stroke  of  the  pumps,  it  is  advisable  to 
provide  the  suction  with  a  foot- valve  and  also 
to  fix  an  air-vessel  in  the  suction  pipes  to 
effect  a  more  gradual  arrest  of  the  water  and 
reduce  the  impact  on  the  pump-valves.  The 
balloon-shaped  air-vessels  retain  the  air  longer 
than  those  of  cylindrical  shape.  The  vessels 
are  made  of  cast-iron,  should  be  of  ample 
strength  according  to  the  pressure  to  be 
borne,  and  be  provided  with  air-cocks  at  the 
top  and  draw-off  cocks  at  the  bottom  to 
admit  air  or  drain  the  rising  main  if  required. 
In  the  United  States  it  is  the  practice  to 
employ  huge  cylindrical  metal  towers  or  tank 
stand-pipes  which  are  frequently  of  sufficient 
capacity  to  serve  as  service  reservoirs,  and 
hold  a  full  day's  domestic  consumption  and 
several  hours'  fire  consumption  of  water,  or 
more.  At  Sandusky,  Ohio,  is  a  stand-pipe 
25  ft.  diameter  and  229  ft.  high.  The  diagram 
(Fig.  2)  illustrates  the  application  of  a 
"  stand-pipe "  to  a  pumping  or  rising  main, 
which  is  brought  into  use  by  closing  the 
valves  A  and  B  when  the  water  passes  over 
the  top  of  stand-pipe  and  gives  the  additional 
"head"  gained  by  its  height — any  surplus 
water  pumped  passing  down  the  third  leg  C 
and  into  the  low  service  reservoir  adjoining. 
The  application  of  an  "  air-vessel "  to  an 
ordinary  delivery  or  pumping  main  is  shown 
diagrammatically  in  Fig.  3. 

Steam-Engines.  —  In  classifying  steam- 
engines  and  machinery  for  waterworks  and 
general  pumping  purposes,  a  great  many 
independent  characteristics  in  regard  to  their 
general  arrangement  of  parts  and  methods  of 
working  must  be  taken  into  consideration. 
They  may,  for  example,  be  divided  into  con- 
densing and  non-condensing,  compound  and 
non-compound,  single  and  double-acting, 
geared  and  direct  coupled,  direct  and  crank- 
shaft, rotative  and  non-rotative,  and  vertical, 
horizontal,  inclined,  or  inverted  cylinder 
engines. 


Non-condensing  engines  exhaust  their  steam 
direct  into  the  atmosphere  or  into  a  receiver 
where  the  pressure  is  greater  than  that  of 
the  atmosphere.  The  steam  is  used  at  full 
pressure  either  partially  or  throughout  the 
stroke,  sufficient  allowance  being  made  to 
"cut  off"  and  avoid  back-pressure.  Con- 
densing engines  exhaust  their  steam  after 
forcing  the  piston  from  the  beginning  to  the 
end  of  the  stroke  into  a  separate  chamber 
termed  a  "  condenser,"  which  is  maintained 
in  a  state  of  partial  vacuum,  the  steam  being 
therein  condensed  by  contact  with  a  nest  of 
tubes  through  or  around  which  cold  water  is 
constantly  circulated  (surface  condensing),  or, 
in  some  forms,  a  jet  of  cold  water  is  sprayed 
into  the  condenser  and  meets  the  incoming 
steam  (jet  condensing).  The  condensed  water 
and  air  are  removed  from  the  condenser  by 
an  air-pump  usually  worked  from  the  engine, 
and  the  water,  having  a  probable  temperature 
of  about  115°  F.,  is  used  for  feeding  the  boilers. 
The  advantages  of  condensing  are  very  con- 
siderable, and  the  process  should  be  adopted 
in  all  but  quite  the  smaller  sized  engines,  as 
a  great  economy  of  steam  consumption  is 
effected  thereby.  Engines  are  classified  as 
compound  or  non-compound  according  to  the 
number  of  expansions  of  the  steam  obtained 
in  the  cylinders.  The  non-compound  or 
simple  engine  consists  of  a  single  cylinder 
in  which  the  steam  does  its  work,  and  is  then 
exhausted  either  directly  into  the  atmosphere 
or  into  a  condenser.  In  the  compound  engine 
the  steam,  after  having  partially  expanded 
'and  done  work  in  the  small  or  high  pressure 
cylinder,  is  exhausted  into  a  larger  or  low- 
pressure  cylinder,  where  it  undergoes  a 
further  expansion  before  being  exhausted  into 
the  condenser.  In  the  triple  and  quadruple 
expansion  engines  the  steam  does  work  in 
three  and  four  successive  cylinders  respec- 
tively before  being  finally  exhausted  into  the 
condenser. 

A  single-acting  engine  is  one  in  which  the 
steam  acts  upon  one  side  of  the  piston  only. 
In  a  double-acting  engine  it  acts  upon  both 
sides  of  the  piston  alternately.  Both  single 


447 


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ENCYCLOPEDIA   OF 


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and  double-acting  engines  are  made  either 
of  the  condensing  or  non-condensing  type. 
Another  important  distinction  in  the  classifi- 
cation of  pumping  engines  and  machinery  lies 
between  geared  and  direct-coupled  machinery. 
In  geared  pumping  machinery  high  speed 
engines  are  employed,  and  the  pumps  are 
driven  therefrom  by  means  of  gearing,  toothed 
wheels,  or  by  means  of  belting,  chains,  or 
ropes.  By  these  means  the  engine  is  usually 
run  at  a  greater  speed  than  the  pumps,  and 
some  economy  of  steam  consumption  per 
indicated  horse-power  should  be  secured. 
Another  advantage  looked  for  in  this  system 
is  that  of  less  capital  cost  for  the  engine  and 
lighter  foundations.  There  will,  on  the  other 
hand,  usually  be  a  lower  mechanical  efficiency 
(probably  not  more  than  from  65  to  75%), 
greater  liability  to  break  down,  increased  wear 
and  tear,  noise,  and  vibration. 

In  direct- coupled  pumping  machinery  the 
pumps  are  connected  to  the  steam  ends,  the 
number  of  reciprocations  of  the  pumps  is  the 
same  as  in  the  engine,  and  the  mechanical 
efficiency  may  be  as  high  as  92  °/0.  There  is 
less  wear  and  tear,  less  liability  to  break 
down,  and  the  vertical  direct-acting  type  of 
machinery  is  usually  the  most  satisfactory  for 
large  stations.  A  distinction  is  also  to  be 
noted  between  direct  and  crank-shaft  with  fly- 
wheel engines.  In  the  direct  engine  the  piston- 
rod  of  the  engine  and  the  piston-rod  or  plunger 
of  the  pump  are  continuous,  there  being  no 
crank-shaft  or  fly-wheel.  Koughly  speaking 
it  may  be  said  that  a  typical  direct-engine 
consists  of  two  cylinders  placed  side  by  side, 
the  admission  of  steam  being  controlled  by 
ordinary  three-ported  slide  valves.  As  the 
piston  of  one  cylinder  is  moving  towards  the 
other  end  of  the  cylinder  it  strikes  a  lever 
actuating  the  slide  valve  of  the  other  cylinder, 
and  in  this  way  each  piston  alternately 
actuates  the  slide  valve  admitting  steam  to 
the  other  cylinder.  Frequently,  however,  one 
of  the  two  cylinders  named  is  simply  a  very 
sir  all  one,  the  function  of  which  is  to  actuate 
the  slide  valve  of  the  large  cylinder.  Engines 
of  this  class  are  quite  self-acting,  convenient, 


and  compact,  but  are  not  economical,  there 
being  no  expansion  of  the  steam.  Of  later 
years,  however,  very  great  improvements  have 
been  made  by  "  compounding  "  and  by  the 
introduction  of  "  high-duty  gear,"  the  function 
of  this  latter  improvement  being  to  absorb  a 
certain  quantity  of  power  at  the  beginning  of 
the  stroke  and  to  give  it  oft'  again  towards  the 
end — the  steam  working  expansively  in  the 
cylinder.  The  most  modern  direct-engines 
embodying  the  latest  improvements  in  the 
economical  use  of  steam  are  thus  amongst 
the  most  efficient  pumping  engines  employed. 

The  "beam  engine"  is  the  earliest  form 
of  crank-shaft  and  fly-wheel  engine,  many 
examples  of  which  are  still  in  use,  though 
this  type  is  gradually  being  superseded.  The 
advantage  of  the  modern  forms  of  crank-shaft 
pumping  engines  is  that  they  lend  themselves 
favourably  to  the  expansive  working  of  steam, 
and  various  ways  are  adopted  in  practice  of 
arranging  the  cylinders  and  cranks  in  the 
compound  and  triple-expansion  engines  of 
this  class.  The  best  form  is  that  in  which 
there  are  three  cylinders,  each  working  a 
pump  by  means  of  a  "  three-throw  "  crank — 
the  cranks  being  placed  at  angles  of  120°. 
From  such  a  pump  the  delivery  of  water  is 
quite  uniform,  which  is  an  important  con- 
sideration, especially  where  the  water  is 
delivered  direct  into  the  distributing  mains. 

When  the  reciprocating  motion  of  the 
piston  of  an  engine  does  work  simply  upon  a 
reciprocating  piece  the  engine  is  termed  non- 
rotative,  but  when  the  work  is  done  upon  a 
continuously  revolving  shaft,  as  is  more 
generally  the  case,  the  engine  is  then  of  the 
rotative  class.  Usually  the  crank  pin  of  the 
revolving  shaft  is  connected  directly  with 
the  piston-rod  by  a  connecting-rod,  and  the 
engine  is  said  to  be  direct-acting.  Engines 
are  also  sometimes  classified  according  to  the 
position  and  arrangement  of  the  cylinder,  and 
are  then  described  as  horizontal,  vertical,  or 
inclined  cylinder  engines  respectively.  If  the 
cylinder  is  above  the  connecting-rod  and 
crank,  as  in  many  vertical  engines,  the  engine 
is  described  as  of  the  inverted  cylinder  class. 


448 


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MUNICIPAL  AND   SANITARY  ENGINEERING. 


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The  duty  or  effective  work  of  a  pumping 
engine  is  expressed  by  stating  the  ratio  of 
the  product  in  foot-pounds  of  the  weight 
of  water  raised  into  the  height  it  has  to  be 
lifted  with  relation  to  1  cwt.  (112  Ibs.)  of 
coal  consumed  in  lifting  the  water.  In 
America  100  Ibs.  of  coal  is  adopted  as  the 
unit  of  measurement,  and  some  misunder- 
standing not  infrequently  arises  by  the 
comparison  of  results  reduced  to  these 
different  standards.  In  refined  experiments 
the  weight  of  ashes  and  clinkers  is  deducted 
and  the  unit  of  fuel  taken  on  the  combustible 
portion  of  the  coal  used.  According  to  the 
dynamic  theory  of  heat,  1  Ib.  of  average 
good  coal  contains  about  14,000  units  of  heat 
which  are  developed  into  a  force  capable  of 
doing  a  definite  amount  of  work  when  burned 
to  produce  steam.  In  actual  practice  a  very 
large  proportion  of  these  heat  units  are  lost 
in  various  ways,  such  as  by  escape  up  the 
chimne}7,  by  condensation  of  the  steam  in 
pipes  and  cylinders,  by  leakage  past  the  piston 
or  valves,  and  by  escape  with  the  exhaust 
steam  into  the  condenser,  so  that  in  the  end 
only  some  10  or  12°/0are  usually  transformed 
into  actual  useful  work.  Any  successful 
efforts,  therefore,  to  reduce  these  several 
sources  of  loss  to  a  minimum  will  result  in 
increased  efficiency  and  economy  of  working. 
The  efficiency  of  the  steam-engine  is  repre- 
sented by  the  ratio  which  the  power  developed 
in  the  cylinders  (stated  in  thermal  units) 
bears  to  the  heat  units  supplied  to  the 
engine. 

The  mechanical  efficiency  of  an  engine  is 
the  inverse  ratio  which  the  I.H.P.  bears 
to  the  power  given  off  at  the  crank-shaft 
or  fly-wheel  (B.H.P.).  The  efficiency  of  the 
pump  is  the  inverse  ratio  of  the  latter  to 
the  work  done.  The  work  done  is  stated  in 
foot-pounds,  and  is  represented  by  the  pro- 
duct of  the  weight  of  water  raised  (in  pounds) 
into  the  actual  lift  or  head  (in  feet). 

The  steam-engine  is  a  heat  engine,  and  the 
true  measure  of  its  efficiency  is  the  amount  of 
heat  consumed  in  the  performance  of  a  definite 
amount  of  useful  work ;  but  as  the  total  units 


of  heat  in  a  pound  of  dry 'steam  differs  but 
little  through  the  pressures  commonly  em- 
ployed,1 it  is  regarded  as  a  sufficiently 
approximate  and  convenient  means  of  com- 
paring the  efficiencies  of  engines  to  state  the 
pounds  of  dry  steam  used  in  the  cylinders  to 
generate  1  h.p.  of  work.  In  good  class 
engines  the  following  results  of  steam  con- 
sumption per  horse-power  hour  are  readily 
obtainable  : — 

Per  Hour. 

Non-condensing  engines  .  25  Ibs.  steam  per  I.H.P. 
Condensing  ,,  .  18  Ibs.  ,, 

Compound  „  .     14  to  16  Ibs.    ,, 

Triple-expansion      ,,  .     12  to  18  Ibs.    ,, 

It  will  also  be  convenient  here  to  state  what 
may  be  considered  good  results  in  coal 
consumption  per  horse-power  for  various 
classes  of  engines  : — 


Non-condensing  engines 
Condensing  ,, 

Compound  ,, 

Triple-expansion      ,, 


Per  Hour. 
3    Ibs.    coal  per   I.H.P. 
2   Ibs. 

H  to  1|  Ibs.     „ 
ijtolilbs.    „ 


A  small  coal  consumption  indicates  an 
economical  engine  and  boiler,  but  a  large 
consumption  does  not  necessarily  prove  the 
reverse,  so  that  the  rating  of  an  engine 
according  to  the  coal  burned  is  not  a  reliable 
method,  as  many  other  questions  are  also 
involved,  such,  for  example,  as  the  quality  of 
the  coal  and  the  manner  of  stoking.  In  any 
trials  for  efficiency  it  is  necessary  to  dis- 
tinguish that  of  the  steam-engine  from  the 
efficiency  of  the  boiler. 

For  further  information  see  also  articles  on 
"  CONDENSING,"  "  INDICATOE,"  "  STEAM  RAISING," 
"ECONOMISERS,"  "HOBSE-POWEE,"  "  BoiLEES," 
"  FUEL."  W.  H.  M. 

Steam  Raising. — In  modern  economical 
steam  raising  various  devices  are  employed 
with  the  object  of  producing  steam  with  a 
minimum  consumption  of  fuel  by  economising 
all  waste  heat  as  fully  as  possible,  and  of 
reducing  the  losses  due  to  condensation  of 
the  steam  during  its  use.  Some  of  the 

1  At  absolute  pressure  of  80  Ibs.  per  square  inch  the 
total  heat  in  1  Ib.  of  steam  from  water  at  32°  F.  is 
1,177  British  thermal  units ;  at  150  Ibs.  pressure  it  is 
1,191-2  units. 


M.S.E. 


449 


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ENCYCLOPAEDIA   OF 


STE 


methods  employed  are,  the  use  of  superheated 
steam,  of  economisers  or  feed-water  heaters, 
steam  dryers  and  purifiers,  and  steam  jacketing. 
SUPERHEATED  STEAM. — Steam  formed  in  an 
open  boiler  under  atmospheric  pressure  (14'7 
Ibs.  per  square  inch)  has  the  same  temperature 
as  the  boiling  water,  212°  F.  When  the  boiler 
is  closed,  as  with  a  weighted  valve,  steam  is 
formed  at  a  higher  temperature,  because  of 
the  greater  pressure.  The  vapour  of  water 
boiled  in  a  partial  vacuum  will  have  a  tem- 
perature below  212°  because  of  the  lower 
pressure.  Steam  formed  in  contact  with 
water,  as  in  an  ordinary  boiler,  and  containing 
watery  particles  is  called  wet  saturated  steam. 
When  all  the  water  has  just  boiled  away  and 
the  saturation  point  is  reached — all  the  latent 
heat  required  for  the  steam  having  been  taken 
up — we  have  dry  saturated  steam.  Saturated 
steam,  which  is  perfectly  dry,  contains  in  a 
given  volume,  and  at  a  given  temperature,  the 
maximum  weight  of  evaporated  water,  and  has 
the  maxima  pressure  and  density  attainable  at 
such  temperature.  Dry  saturated  steam  is 
only  approximated  to  in  practice  by  providing 
domes  to  boilers  in  order  to  remove  the  steam 
as  far  as  possible  from  the  water.  Applying 
heat  still  further,  after  having  removed  the 
steam  from  the  presence  of  water,  it  becomes 
surcharged  with  heat,  and  is  then  said  to  be 
superheated  steam,  that  is,  steam  which  has 
its  temperature  raised  above  formation  point. 
The  more  it  is  heated  the  more  nearly  will  its 
properties  approach  those  of  a  perfect  gas. 
Superheated  steam  cannot  exist  in  the  presence 
of  water,  as  the  latter  will  absorb  the  surplus 
of  superheat  and  the  steam  thus  reverts  to 
the  saturated  state.  The  advantages  to  be 
derived  from  the  use  of  superheated  steam  are 
the  prevention  of  condensation  and  consequent 
fall  in  steam  pressure  in  passing  from  the 
boiler  to  the  engine,  and,  in  the  engine,  the 
elimination  of  condensation  losses  within  the 
cylinder  due  to  exchange  of  heat  between  the 
steam  and  metal  cylinder  walls.  The  object 
to  be  achieved  therefore  is  to  deliver  the  steam 
into  the  cylinder  with  such  surplus  heat  as 
will  prevent  condensation,  thus  keeping  the 


steam  as  dry  as  possible  throughout  the 
stroke.  The  advantages  of  superheating  were 
demonstrated  by  Him  as  long  ago  as  1855, 
but  troubles  were  experienced  at  the  super- 
heater, and  the  cylinder  lubricants  were 
burned  up,  resulting  in  the  abandonment  of 
the  process  in  1870.  Upon  the  introduction 
of  safer  superheaters  and  heavy  mineral 
lubricating  oils  the  original  objections  were 
removed,  and  a  revival  of  superheating  has 
taken  place  since  1890,  producing  an  important 
improvement  in  the  thermodynamic  economy 
of  engines.  The  gain  from  superheating  may 
be  taken  at  an  average  of  about  25%,  but 
varies  from  10  to  50%  with  50°  to  100°  of 
superheat  according  to  the  efficiency  of  the 
engine.  Mr.  M.  Longridge  has  given  it  as  his 
opinion  that  400°  F.  of  superheat  in  the 
cylinder  is  sufficient  to  prevent  initial  con- 
densation, and  that  the  superheater,  to  be 
efficient,  should  have  a  head  of  about  400°  F. 
above  the  temperature  of  the  superheated 
steam.  In  practice,  the  steam  to  be  super- 
heated is  led  off  from  the  boiler  into  a  separate 
vessel  or  accessory  appliance  called  a  "  super- 
heater," and  in  which  it  is  subjected  to  the 
additional  heat.  Superheaters  are  either  of 
the  flue-fired  class  or  are  independently-fired. 
Flue-fired  superheaters  are  placed  in  the 
down-takes  of  Lancashire  and  Cornish  boilers, 
where  they  are  heated  by  the  gases  from  the 
furnace  flues,  thus  utilising  what  would  other- 
wise pass  away  as  waste  heat.  With  boilers 
of  the  water-tube  class  independently-fired 
superheaters  are  mostly  used.  Some  highly 
economical  results,  not  obtainable  from  steam 
in  any  other  way,  have  been  obtained  by  Mr. 
Schmidt,  whose  experiments  have  shown  it 
possible  to  employ  steam  superheated  by  as 
much  as  300°  F.  In  trials  of  the  Schmidt 
engine  and  superheater,  the  consumption  of 
steam  has  been  well  below  10  Ibs.  per  Indicated 
H.P.  hour,  and  the  consumption  of  coal  in 
boiler  and  superheater  together,  it  was  found, 
was  as  low  as  1'3  Ib.  per  Indicated  H.P.  even 
with  small  engines.  In  these  trials,  after  the 
hot  gases  had  passed  the  superheater,  as  much 
of  the  remaining  heat  was  utilised  as  possible 


450 


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MUNICIPAL  AND   SANITAEY  ENGINEERING. 


STE 


in  an  economise!'  or  feed  water-heater  for  the 
interception  and  return  of  the  heat  to  the 
boiler. 

STEAM:  EQUIVALENT  WEIGHT  OF  WATER  AS 
EVAPORATED  FROM  AND  AT  212°  F. — For  the 
purpose  of  comparing  evaporative  boiler  tests, 
the  results  obtained  must  be  reduced  to  a 
common  standard,  which  is  usually  reckoned 
from  and  at  212°  F.  The  method  of  calcu- 
lating these  results  will  be  best  understood  by 
the  following  example  : — 

From  the  tests  made,  suppose  that  1  Ib.  of 
the  coal  used  has  been  found  to  evaporate 
9'71  Ibs.  of  water,  with  boiler  feed  at  145°  F. 
and  steam  pressure  90  Ibs.  per  square  inch,  as 
shown  by  the  gauge.  Steam  at  90  Ibs.  gauge 
pressure  is  equivalent  to  90  -f-  15  Ibs.  (atmo- 
spheric pressure),  that  is,  105  Ibs.  absolute.  By 
reference  to  Regnault's  tables  of  the  properties 
of  saturated  steam  (to  be  found  in  the  majority 
of  engineering  pocket-books),  it  will  be  seen 
that  the  temperature  of  steam  at  105  Ibs. 
absolute  is  331*3°  F.,  and  also  that  the  total 
heat  in  1  Ib.  of  steam  at  that  pressure  from 
water  at  32°  F.  is  1,183  British  thermal  units. 

The  latent  heat  in  1  Ib.  of  steam  at  212°  F. 
is  966'6  British  thermal  units  (see  tables), 
and  the  equivalent  weight  of  water  evaporated 
per  pound  of  coal  from  and  at  212°  F.  is  there- 
fore represented  by  the  following  equation : — 


W  = 


H 


(t  -  32°) 

-   X  w, 


966-6 


in  which,  — 

W  =  the  equivalent  weight  of  water  evapo- 
rated from  and  at  212°  F.  ; 

H  =  total  heat  of  steam  (in  British  thermal 
units)  at  the  temperature  corresponding  to  the 
pressure,  from  water  at  32°  F.  ; 

t  =  temperature  of  boiler  feed  during  the 
test; 

w  =  weight  of  water  actually  evaporated 
per  pound  of  coal  from  temperature  (i)  of  feed. 

Substituting  the  numerical  values  in  the 
above  example,  we  have  — 


x  9.71 


W  = 


'b 


X  9-71  =  10-748  Ibs. 


Sterilisation  of  Water  can  be  effected  by 
(1)  heat,  (2)  filtration,  (3)  certain  chemical 
agents. 

(1)  HEAT.— Boiling  is  an  efficient  means  on 
a  small  scale,  but  the  expense  is  prohibitive 
when  large  quantities  have  to  be  regularly 
dealt  with,  and  the  resultant  liquid  is  de- 
aerated  and  less  palatable.  In  the  Eouart, 
Geneste-Herscher,  and  Vaillard-Desmaroux 
sterilisers  the  water  is  heated  for  a  short  time 
to  113-116°  C.  in  a  closed  vessel,  or  a  system 
of  coils,  whereby  the  outgoing  is  made  to  heat 
the  incoming  water,  at  the  same  time  being 
itself  cooled  to  near  the  ordinary  temperature. 
In  this  way  the  natural  gases  are  retained, 
very  little  earthy  deposit  occurs,  and  the 
sterilised  water  is  protected  from  air.  A 
deposit,  however,  does  accumulate,  and  the 
narrow  coils  sometimes  block,  and  are  difficult 
to  clean.  In  the  Forbes  apparatus,  used  in 
the  United  States  army,  the  water  is  only  boiled 
for  a  few  seconds,  so  that  it  preserves  most  of 
its  original  gas  and  taste  ;  it  then  passes  over 
a  weir  into  a  temperature  exchanger.  The 
working  is  regulated  by  a  valve.  Other  types 
used  in  America  are  the  Kny-Scheerer, 
Maignen,  and  Von  Siemens.  In  England  the 
Lawrence  steriliser  and  softener  has  been  in  use 
for  some  time  at  Guy's  Hospital  and  elsewhere. 
Its  boiler  is  a  vertical  cylinder  fitted  with 
depositing  trays  above  the  water  line  and 
plates  called  "  locators  "  below  it.  The  water 
boils  up  over  the  trays  and  deposits  its  lime 
and  magnesia  carbonates  on  the  trays  and 
locators  (which  are  removable  for  renewal  or 
cleaning),  and  passes  to  an  interchanger.  The 
writer's  results  with  different  heat  sterilisers 
showed  that  sterility,  even  with  very  varying 
rates  of  flow,  can  with  care  be  insured. 

FILTRATION. — Sand  and  mechanical  filters  in 
good  condition,  and  under  favourable  circum- 
stances, yield  a  sterile  effluent,  but  such  a 
result  can  only  be  depended  upon  with  a  much 
finer  medium.  The  only  filter  that  has  stood 
all  tests  is  the  Pasteur- Chamberland  "  candle  " 
filter  of  biscuit  porcelain,  in  which  the  water 
passes  from  the  outside  inwards,  under  pres- 
sure from  the  main,  a  force  pump,  or  exhaust. 


451 


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ENCYCLOPAEDIA  OF 


STO 


The  tube  is  very  carefully  cleaned,  and  should 
be  sterilised  by  boiling  at  intervals.  The 
average  yield  per  tube  is  estimated  at  £  gallon 
per  day  with  only  an  ordinary  head  of  water, 
and  8  gallons  per  day  with  pressure.  The  tubes 
can  be  arranged  in  "batteries  "  of  any  number, 
and  the  joints  must  be  carefully  attended  to. 

CHEMICAL  AGENTS. — For  chlorine,  ozone,  and 
permanganate,  see  respective  articles  and 
"  CONDY'S  FLUID."  It  has  long  been  known 
that  acids  generally,  and  many  metallic  salts, 
are  antagonistic  to  bacteria,  but  for  sterilisa- 
tion of  ordinary  water  an  agent  is  required 
which  is  not  costly  and  is  non-poisonous  to 
higher  life,  and  this  limits  the  application  to 
special  cases. 

0*072  °/0  of  sulphuric  acid  is  effective  against 
B.  typhosus  in  15  minutes,  and  62  grains  per 
gallon  is  sufficient  to  destroy  typhoid  organisms 
in  the  usual  drainage  from  an  isolation  hos- 
pital or  other  infected  area.  B.  enteritidis 
Sp.  cholera,  intestinal  worms  and  ova,1  are 
also  killed,  and  the  free  acidity  is  soon 
neutralised  on  mixture  with  ordinary  sewage. 
For  sterilising  water  in  campaigns  bisulphate 
of  soda,  15  grains  per  pint,  is  portable  and 
effectived 

With  the  same  object  Schumberg  in  the 
German  army  has  used  bromine,  6  parts  per 
100,000,  followed  by  a  tablet  of  sodium  sul- 
phite and  mannite,  but  among  the  objections 
have  been  the  difficulty  of  transporting  the 
bromine,  and  the  presence  of  bromides  in  the 
water.3  Allain  at  Marseilles  used  iodine,  and 
Nesfield  in  India  has  employed  a  tablet  con- 
taining iodide  and  iodate  and  another  contain- 
ing tartaric  or  citric  acid;  together,  when 
used  as  directed,  they  liberate  5  parts  of 
iodine  per  100,000  of  water;  after  2  to  5 
minutes  any  excess  of  iodine  is  removed  by  a 
tablet  of  sodium  sulphite.  The  writer  found 
that  the  sterilisation  was  satisfactory.4  (See 

1  Valerio,  "  Bull.  Soc.  Vaudoise  Sci.  Nat.,"  1902, 
No.  143. 

2  Parkes  and  Eideal,  "  Epidem.  Soc.,"  1901 ;  Lancet, 
Jan.  26th,  1901. 

8  Public  Health,  Sept.,  1902,  p.  709. 
*  J.  of  Prevent.  Medicine,  Oct.,  1905  ;  Indian  Med. 
Gaz.,  Aug.,  1905. 


IN  WATER  SUPPLIES  "  ;  "  FILTERS, 
DOMESTIC  "  ;  "  FILTRATION  " ;  "  WATER  SUPPLY, 
DOMESTIC.") 

Copper  salts  in  small  quantities  have  been 
repeatedly  tried.  One  in  8,500  of  the  sulphate, 
or  1  in  13,500  of  the  chloride,  kills  B.  coli 
in  3  hours ;  1  in  7,000  of  sulphate,  or  1  in 
10,000  of  chloride,  kills  Staph.  aureus  in  2 
hours.  One  in  1  to  10,000,000  prevents  the 
growth  of  algse,  and  in  this  small  quantity  it 
is  not  poisonous  to  man  or  to  fish,  and  is 
removed  after  a  time  by  natural  precipi- 
tation.1 S.  E. 

Storm-water. — The  quantity  of  storm- 
water  or  dilute  sewage  coming  down  to  the 
outfall  works  during  rainy  periods  is  a  very 
variable  quantity  in  different  districts.  The 
proportion  of  the  total  rainfall  reaching  the 
sewers  depends  largely  upon  the  character  of 
the  district ;  obviously,  a  much  greater  flow 
would  be  experienced  from  a  hilly  area  with  a 
clay  or  other  impervious  soil  than  would  be 
derived  from  a  flat  chalky  or  other  porous  and 
absorbent  area.  The  extent  to  which  the 
district  is  built  upon,  and  the  proportion  of 
paved  areas,  also  influences  the  total  of  storm- 
water  to  be  provided  for.  Another  feature  is 
the  condition  of  soundness,  or  otherwise,  of 
the  sewers  and  the  consequent  extent  to  which 
subsoil  water  may  be  able  to  gain  access 
thereto.  Where  the  sewers  are  old,  leaky,  of 
porous  or  defective  brickwork,  and  such  like, 
the  amount  of  subsoil  water  draining  away 
through  them  may  easily  be  far  in  excess  of 
the  sewage  proper.  The  ordinary  dry  weather 
flow  of  sewage  should  closely  approximate  to 
the  amount  of  the  water  supply  of  the  district. 
This  may  be  anything  from  about  25  gallons 
to  35  gallons  per  head  per  day.  All  sewage 
flow  beyond  this  amount  would,  therefore,  be 
due  to  rainfall  or  subsoil  soakage,  and,  to  a 
less  extent,  in  some  cases  to  manufacturers' 
wastes,  in  so  far  as  the  water  supply  for  such 

1  "  Bulletin  U.S.  Department  of  Agriculture,"  1903 ; 
"  Zeits.  f.  Hyg.,"  1903,  p.  495  ;  J.  B.  San.  Inst.,  1904, 
p.  591;  ibid.,  1906,  p.  556;  J.  Prevent.  Med.,  July, 
1904;  "  Chem.  Centralblatt,"  1900,  ii.,  203. 


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trades  was  derived  otherwise  than  from  the 
town  supply.  In  a  very  hilly  district  the 
storm-water  is  more  difficult  to  cope  with  than 
in  one  of  a  less  undulating  character,  because 
in  the  former  case  the  storm-flow  is  relatively 
larger  and  reaches  the  outfall  works  much 
more  suddenly.  In  other  words,  the  rate  of 
flow  is  more  rapid,  though  of  possibly  shorter 
duration,  and  the  provision  to  be  made  for 
the  reception  of  such  abnormal  discharges 
must  be  relatively  larger  and  more  complete 
than  in  cases  where  the  delivery  is  less  violent. 
One  inch  of  rainfall  in  an  hour  occurs  but 
seldom  in  this  country,  as  in  the  case  of  excep- 
tionally severe  storms,  so  that  a  provision  of 
sewer  capacity  to  remove  that  amount  should 
be  ample.  In  fact,  to  further  increase  the 
sizes  of  sewers  beyond  this  limit  would 
seriously  decrease  their  efficiency  under 
ordinary  working  conditions,  besides  greatly 
enhancing  the  cost  of  sewering  the  district 
without  any  proportionate  advantage.  The 
London  sewers  were  designed  to  remove  only 
*01  in.  of  rainfall  per  hour  in  addition  to  an 
allowance  of  5  cu.  ft.  of  sewage  per  head  per 
day.  It  was  estimated  that  only  five-eighths 
of  this  rainfall  would  reach  the  sewers — the 
remaining  three-eighths  being  evaporated  or 
absorbed.  Experience  has  shown  that  this 
allowance  is  too  small.  The  sewerage  system 
for  Edinburgh  gives  provision  for  42  gallons 
per  head  per  day,  one-half  of  this  to  flow  off  in  8 
hours.  Only  in  exceptional  cases  would  the 
flow  exceed  50  gallons  per  head  per  day.  In 
some  districts  small  natural  streams  find  their 
way  into  the  sewers,  and  these  in  rainy 
periods  become  quickly  swollen,  so  that  the 
ordinary  calculations  of  the  volume  of  storm- 
water  to  be  dealt  with  are  not  applicable  to 
such  cases.  There  is  no  doubt  that  the  first 
flush  of  storm -water  delivered  at  the  outfall 
is  very  foul  and  heavily  laden  with  suspended 
matter,  especially  where  the  main  sewers  are 
in  a  defective  condition.  Storm  overflows  or 
reliefs  should  therefore  not  come  into  action 
until  the  rate  of  flow  has  increased  to  several 
times  the  normal.  The  provision  of  such 
"  reliefs"  or  overflows  is  an  essential  part  of 


the  sewerage  system.  In  a  hilly  district  their 
absence  might  readily  lead  to  the  bursting  of 
a  main  sewer  owing  to  the  volume  of  water 
coming  down  from  the  higher  parts  of  the 
district  heading  up  for  the  want  of  a  free 
outlet,  and  so  unduly  increasing  the  pressure 
within  the  sewer.  The  flooding  of  premises 
in  the  lower  parts  along  the  line  of  sewer 
would  also  result. 

There  is  a  difficulty  in  fixing  storm  over- 
flows to  pass  sewage  at  any  fixed  or  uniform 
degree  of  dilution  because  the  ordinary 
flow  in  sewers  varies  throughout  the  24 
hours — the  sewage  coming  down  during 
the  morning  hours,  say  8  a.m.  to  12  noon, 
is  many  times  greater  than  the  night 
flow  from,  say,  8  p.m.  to  6  a.m.,  so  that 
if  the  overflow  is  fixed  for  a  dilution  of  six 
times  the  morning-flow,  the  night-flow,  owing 
to  its  smaller  volume,  will  necessarily  be 
diluted  to  a  much  larger  extent  before  any 
liquid  passes  the  storm-overflow,  and,  as  a 
result,  the  purification  works  will  be  saddled 
with  a  larger  quantity  of  weak  sewage  during 
the  night  than  is  necessary.  Purification  works 
are  much  relieved  by  the  provision  of  separate 
sewers  for  storm-water,  as  distinct  from  soil 
sewers,  but  in  cases  where  the  sewage  is 
discharged  into  the  sea  a  combined  system 
will  be  most  economical.  Dr.  Houston,  the 
expert  bacteriologist  engaged  by  the  Eoyal 
Commission  on  Sewage  Disposal,  upon  inves- 
tigations in  this  connection  regards  storm- 
waters  as  being  "  as  potentially  dangerous 
to  health  as  normal  crude  sewage,"  but 
recognises  the  impracticability  of  treating 
the  whole  flow  during  storms.  Where 
sewage  farms  are  in  use  for  dealing  with 
the  sewage  an  ample  area  of  pasture  land 
should  be  specially  reserved  for  the  overflow 
of  storm-water.  Such  storm-water  areas  should 
not  be  used  for  taking  part  of  the  ordinary 
flow  of  sewage,  but  should,  as  far  as  possible, 
be  reserved  in  a  condition  of  readiness  to 
receive  large  volumes  of  dilute  sewage  for 
short  periods.  The  treatment  should  be  one 
of  surface  irrigation  without  under-drainage.  0 

Where  land  is  not  available,  it  has  been  the 


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practice  of  late  years  to  provide  special  storm- 
water  filters  which  act  as  mechanical  strainers 
of  the  suspended  matters  from  storm- 
waters  and  pass  the  liquid  at  the  rate  of  about 
500  gallons  per  square  yard  per  day.  These 
have  frequently  been  simple  excavations  in 
the  earth,  filled  with  gravel,  broken  stone  or 
clinker,  but  they  have  not,  generally  speaking, 
proved  very  satisfactory,  and,  on  the  whole,  do 
not  justify  their  cost.  The  money  spent  in 
the  construction  of  storm-water  beds  would, 
in  most  cases,  be  more  advantageously  used 
in  the  provision  of  larger  permanent  filters 
upon  which  the  ordinary  flow  of  sewage  is 
treated.  By  this  means  the  whole  area  of 
beds  may  be  kept  in  a  mature  and  working 
condition,  and  a  better  average  effluent  pro- 
duced, as  the  filtration  can  be  done  at  a  slower 
rate  per  volume  of  material.  Special  storm- 
filters,  on  the  other  hand,  lie  idle  for  long 
periods,  and  the  money  spent  on  their  con- 
struction is  thus  not  continually  employed  to 
the  best  advantage.  The  filters,  too,  become 
dry,  and  their  oxidising  efficiency  is  much 
impaired. 

The  Eoyal  Commission  on  Sewage  Disposal 
(fifth  report,  1908)  report  unfavourably  upon 
storm-filters,  to  the  effect  that  they  "  are  not 
usually  efficient  and  should  not  be  provided," 
but  that  the  ordinary  dry  weather  flow  beds 
should  be  increased  by  1^  times  so  as  to  allow 
of  the  filtration  of  three  times  the  mean  dry 
weather  flow  by  working  at  a  permissible 
increased  rate  during  storms.  The  Com- 
missioners think  it  is  practicable  to  filter  this 
quantity — viz.,  three  times  the  mean  dry 
weather  flow — and  they  doubt  whether,  as  a 
general  rule,  the  filtration  of  any  larger 
amount  will  be  found  to  be  necessary  to 
prevent  nuisance. 

Dealing  with  the  past  practice  of  the  Local 
Government  Board  in  the  matter  of  storm- 
water,  the  Commissioners  observe  that  "  the 
usual  requirements  of  the  Local  Government 
Board  in  regard  to  the  treatment  of  storm- 
sewage  are  that  any  increase  in  flow  up  to 
,three  times  the  normal  dry  weather  rate 
should  be  fully  dealt  with  by  the  ordinary 


complete  plant,  and  that  a  certain  number  of 
additional  dilutions — up  to  a  total  of  six — 
should  be  treated  on  special  storm-filters.  These 
requirements  should,  we  think,  be  modified  ; 
they  are,  in  our  opinion,  not  sufficiently 
elastic,  and,  moreover,  experience  has  shown 
that  special  storm-filters,  which  are  kept  as 
stand-by  filters,  are  not  efficient.  We  find 
that  the  injury  done  to  rivers  by  the  discharge 
into  them  of  large  volumes  of  storm-sewage 
chiefly  arises  from  the  excessive  amount  of 
suspended  solids  which  such  sewage  contains, 
and  that  these  solids  can  be  very  rapidly 
removed  by  settlement.  We  therefore  recom- 
mend, as  a  general  rule,  that — (1)  Special 
stand-by  tanks  (two  or  more)  should  be  pro- 
vided at  the  works  and  kept  empty  for  the 
purpose  of  receiving  the  excess  of  storm-water 
which  cannot  properly  be  passed  through  the 
ordinary  tanks.  As  regards  the  amount 
which  may  be  properly  passed  through  the 
ordinary  tanks,  experience  shows  that  in 
storm  times  the  rate  of  flow  through  these 
tanks  may  usually  be  increased  up  to  about 
three  times  the  normal  dry  weather  rate  with- 
out serious  disadvantage ;  (2)  Any  over-flow 
at  the  works  should  only  be  made  from  these 
special  tanks,  and  this  overflow  should  be 
arranged  so  that  it  will  not  come  into  opera- 
tion until  the  tanks  are  full ;  (3)  No  special 
storm-filters  should  be  provided,  but  that  the 
ordinary  filters  should  be  enlarged  to  the 
extent  necessary  to  provide  for  the  filtration 
of  the  whole  of  the  sewage,  which,  according 
to  the  circumstances  of  the  particular  place, 
requires  treatment  by  filters." 

W.  H.  M. 

Street  Cleansing. — Necessity  and  Objects- 
Orderly  System — Mechanical  Sweepers — Disposal 
of  Refuse — Removal  of  Snow. 

NECESSITY  AND  OBJECTS. — It  is  important, 
in  order  to  maintain  a  high  standard  of 
public  health,  that  the  streets  of  all  towns  be 
cleansed.  Wet  and  muddy  streets  cause 
dampness  in  the  subsoil,  and  the  moisture 
arising  therefrom  contaminates  the  atmo- 
sphere. Over-dry  streets  and  roadways  wear 


454 


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MUNICIPAL  AND   SANITARY  ENGINEERING. 


STR 


badly,  the  surface  becomes  covered  with  gritty 
particles,  and  detritus  is  soon  ground  up  by 
the  traffic  into  fine  dust,  which  is  easily  blown 
about,  and  becomes  injurious  to  tradesmen's 
goods  and  to  the  public  health.  The  exist- 
ence of  mud  increases  the  difficulty  of 
traction,  renders  the  surfaces  of  pavements 
and  roads  slippery  and  dangerous,  especially 
when  paved  with  wood  and  asphalte.  These 
materials  become  exceedingly  slippery  when 
covered  by  a  thin  greasy  film  of  mud,  but 
if  kept  clean,  even  though  wet,  are  safe  to 
travel  on.  It  is  therefore  necessary  to  keep 
streets  clean  for  sanitary  reasons,  for  safety 
to  traffic,  for  personal  comfort,  and  also  for 
the  sake  of  appearance.  Colonel  Haywood 
ascertained  the  respective  quantities  of  dust 
arising  from  the  worn  road  surface  of  a  granite 
pavement,  and  the  amount  of  detritus  collected 
each  day.  The  wear  which  took  place  on 
3-in.  Aberdeen  Granite  setts  in  9  years  over 
an  area  of  3,950  super,  yds.  was  equal  to 
2  in.  measured  vertically.  This  amounted 
to  219f  cu.  yds.,  and  in  the  state  of  fine 
powder  would  probabty  amount  to  about  one- 
tenth  of  a  cubic  yard  per  day.  The  amount  of 
detritus,  however,  removed  daily  in  fine 
weather  was  30  times  that  quantity,  thus  illus- 
trating the  necessity  of  cleansing  paved  as 
well  as  macadam  surfaces.  Paved  surfaces 
produce  much  less  dust  from  ground-up 
materials,  as  compared  with  macadam,  but 
they  require  frequent  cleansing  to  keep  them 
from  becoming  slippery  and  unsightly,  and 
the  difference  in  cost  is  not  so  great  as  might 
at  first  sight  appear,  but  in  times  of  frost, 
falls  of  snow,  or  wet  weather,  there  is  a  decided 
saving  in  the  cleansing  of  paved  roads. 

To  ensure  success  in  street  cleansing  well 
organised  plans  must  be  thought  out  so  as  to 
systematically  cleanse  all  the  streets  in  the 
district  within  reasonable  spaces  of  time. 
Gangs  of  men  should  be  so  arranged  that  the 
main  roads  are  swept  first  and  the  side  roads 
after.  To  these  gangs  separate  and  distinct 
districts  should  be  given  and  the  work  so 
arranged  that  all  streets  within  each  district 
are  cleansed  at  least  once  a  \veek.  The  first 


part  of  the  work  (viz.,  cleansing  main  streets) 
should  be  commenced  in  the  early  morning 
by  the  mechanical  broom,  if  the  surfaces  and 
weather  are  suitable  for  its  use.  After  this 
has  swept  the  detritus  to  the  sides  of  the 
roads,  small  gangs  of  from  four  men  to  six  men 
should  follow  up  with  hand-brooms,  shovels 
and  carts,  and  pick  up  this  detritus  and  cart  it 
away  to  the  slop  shoot.  Main  streets  through 
busy  towns  should  be  cleansed  at  least  once  a 
day,  and  all  the  work  on  them  (except  the 
removal  of  horse-droppings)  done  by  6  A.M. 

ORDERLY  SYSTEM. — This  is  a  system  in 
which  men  or  boys  remove  the  horse-droppings 
and  other  detritus  on  the  surface  at  once. 
They  are  provided  with  either  small  scoops  and 
short-handled  brushes  only,  or  with  orderly 
trucks  and  the  scoop  and  brush.  In  the 
former  case,  the  droppings,  &c.,  collected  are 
deposited  into  orderly  bins  placed  at  the  side  of 
the  road,  and  which  are  emptied  at  night-time. 
These  bins  are  now  being  replaced  in  several 
towns  by  collecting  pits  sunk  beneath  the  foot- 
path, close  to  the  kerbs,  and  covered  over  by 
hinged  doors.  Openings  are  left  in  the  side 
facing  the  channel  through  which  the  droppings 
are  pushed.  These  pits  are  emptied  at  night 
and  can  then  be  used  as  store  places  for  orderly 
barrows,  brooms,  scrapers  and  squeegees.  In 
some  cities  and  towns  the  orderly  boys  place  the 
refuse  removed  from  the  roads  into  bags  pro- 
vided for  that  purpose,  and  which  are  suspended 
from  hooks  on  the  side  of  a  hand-cart.  This 
is  the  system  adopted  in  Paris,  where  the  bags 
are  usually  placed  inside  a  light  wrought-iron 
hand-cart,  some,  however,  being  suspended  on 
the  outside  in  certain  cases.  The  bag  system 
saves  considerable  time  in  the  collection  of  the 
refuse,  and  the  offensive  process  of  emptying 
the  orderly  bins  or  pits  is  done  away  with. 
The  bags  used  should  be  of  thick  canvas  and 
be  made  with  iron  framed  lips,  and  with 
handles  for  carrying  or  hanging  on  to  the  hooks 
on  the  hand-carts.  In  Paris  a  large  number 
of  women  and  boys,  as  well  as  men,  are 
employed  in  street  cleansing.  They  commence 
from  3  A.M.  to  4  A.M.,  according  to  the  season 
of  the  year,  and  finish  an  hour  before  midday. 


455 


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In  the  city  of  London  principally  men  and 
boys  are  employed  in  this  work.  The  men 
cleansers  commence  work  at  8  P.M.  and  con- 
tinue through  the  night  until  morning,  and 
the  orderly  boys  commence  work  an  hour 
before  the  scavengers  leave  work,  and  con- 
tinue during  the  day.  The  system  by  which 
men  are  employed  in  the  early  part  of  the 
night  from  9  P.M.  to  1  A.M.,  or  5  A.M.  to  9  A.M. 
in  the  main  thoroughfares,  and  the  adoption  of 
boys  during  the  day-time,  should  work  well  in 
provincial  towns.  The  men  who  cease  work 
on  the  main  thoroughfares  will  continue  during 
the  day  cleansing  the  minor  streets  and 
other  places. 

MECHANICAL  SWEEPERS. — These  were  first 
introduced  by  Sir  Joseph  Whitworth.  There 
are  many  makes  of  these  upon  the  market. 
The  general  principle  is  to  attach  a  series  of 
broad  brooms  of  varying  width  (about  30  in.) 
to  endless  chains  turning  upon  pulleys  attached 
to  a  wrought-iron  frame,  the  whole  apparatus 
being  attached  to  the  back  of  a  cart,  having  its 
body  near  the  ground.  The  pulleys  are 
attached  to  the  cart-wheels  and  revolve  with 
them.  The  sweepings  are  carried  up  an 
inclined  plate  and  drop  into  the  body  of  the 
cart.  The  brooms  can  be  raised  or  lowered  by 
hand.  Haulage  can  be  accomplished  either  by 
horse  or  motor-power.  When  the  mud  is  in  a 
stiff  condition,  a  water-cart  should  precede  the 
sweeper  to  convert  the  mud  into  slop,  when 
it  can  easily  be  swept  up.  The  brushes  last 
about  180  hours,  and  it  is  estimated  that  the 
machine  is  equal  to  the  work  of  10  men. 

DISPOSAL  OF  EEFUSE. — Many  methods  are 
adopted  for  the  disposal  of  street  sweepings. 
The  slop,  after  being  removed  from  the  streets, 
is  carted  to  waste  lands  or  special  slop  shoots 
where  quarries  or  disused  pits  are  to  be  filled 
up.  Street  sweepings  and  horse-droppings  are 
sold  or  given  to  farmers  as  manure.  On  no 
account  should  road  sweepings  be  sent  to 
building  sites  for  making  up  uneven  surfaces. 
Epidemics  of  disease  are  liable  to  be  caused 
by  this  system.  Where  cost  will  permit, 
the  best  method  undoubtedly  is  to  burn  all 
street  sweepings  (with  the  exception  of  horse- 


droppings,  which  can  often  be  disposed  of  for 
manure)  as  soon  as  possible  after  collection. 
If  this  is  impracticable,  H.  P.  Bulnois,  in  the 
"  Municipal  and  Sanitary  Engineers'  Hand- 
book," suggests  that  where  possible  they  should 
be  taken  out  and  dropped  into  the  sea  in  large 
hopper  barges  and  sunk  in  deep  water.  It 
may,  however,  be  possible  to  wash  them  at  a 
small  cost,  and  they  can  then  be  used  as  a 
matrix  for  mortar. 

REMOVAL  OF  SNOW. — This  is  always  a  diffi- 
cult and  costly  matter.  Snow  should  not  be 
removed  while  the  fall  continues,  but  directly 
it  ceases,  all  available  men  and  carts  should  be 
employed.  Snow-ploughs  are  used  for  clear- 
ing the  roadways,  these  being  usually  con- 
structed of  wood,  and  loaded  when  in  use  by 
being  filled  with  snow  or  stones.  Two  or  more 
rough-shod  horses  are  required  to  draw  an 
ordinary  plough,  and  great  care  must  be  taken 
in  using  it  that  damage  to  the  road  surface 
is  prevented.  Sand  should  be  sprinkled  on 
the  roads  and  footpaths  to  prevent  slipperiness 
in  frosty  weather  and  after  the  removal  of 
snow.  Receptacles  containing  sand  or  fine 
gravel  for  sprinkling  by  hand  labour  should 
be  placed  at  convenient  intervals  along  the 
streets,  especially  in  those  paved  with  wood 
or  asphalte.  Space  should  be  first  cleared 
in  the  main  thoroughfares,  to  allow  of  a 
double  line  of  traffic,  the  snow  being  heaped 
in  ridges  at  the  sides  of  the  road,  and  openings 
cut  at  frequent  intervals  for  pedestrian  traffic. 
The  channels  should  be  left  clear  in  the  case 
of  a  sudden  thaw.  Salt  has  been  used  of 
recent  years  to  assist  in  the  removal  of  snow 
from  the  carriage-ways,  with  good  results.  It 
should  be  spread  as  soon  as  any  considerable 
amount  of  snow  has  fallen,  as  the  traffic  hastens 
the  melting  process.  The  slush  formed  can 
be  easily  swept  to  the  sides  of  the  road  by  the 
machine-broom  and  carted  away,  water-carts 
following  up  this  process  to  wash  the  remain- 
ing slush  and  mixture  off  the  surface.  Salt 
has  no  detrimental  effect  on  wood,  granite, 
or  asphalte  carriage-ways,  but  causes  con- 
siderable damage  to  macadamised  carriage- 
ways, owing  to  the  quantity  of  mud  formed. 


456 


STR 


MUNICIPAL   AND   SANITAEY  ENGINEEEING. 


SUB 


The  amount  of  salt  necessary  depends  entirely 

upon  the  conditions   and   amount   of   traffic. 

Foot-paths   should    be  cleared  as  rapidly    as 

possible,   salt   being   used   for   this    purpose. 

The    slush    formed    by   the    salt   should   be 

removed    very     quickly 

owing  to   the    great  danger 

to  the  health  of  the  public, 

caused      by      the-     lowered 

temperature.       The     snow 

should  be  shovelled  into  carts 

and   deposited    upon    waste 

land  and  left  to  thaw.     The 

system  of  tipping  the  snow 

down  the  manholes  into  the 

sewers  is  adopted  in  many 

towns,    but    care    must    be 

taken    that    the    snow   does 

not  block  up  the  sewer,  as 

it  takes  a  considerable  time 

to  melt.     Where   a  town  is 

near  a  river  the  snow  should 

be  tipped  into  it. 

F.  L.  &  E.  H.  B. 

Streets.    (See  "  EOADS  AND 
STREETS.") 

Subsoil    Drainage,— 

Extensive   drainage  of  land 
renders  the  climate  drier  and 
more  healthy  by  lowering  the 
level    of   subsoil  water   and 
removing  the   miasmatic  or 
malarial    influences    which 
accompany    low-lying     clay 
and  water-logged,  or  marshy, 
soils.      The    land    itself    is 
rendered   more   pervious   to 
the  action  of  the  air,  so  that 
the   oxidation  of  waste  pro- 
ducts occurs  more  readily  and  germination  is 
promoted,  making  bogs  and  marshes  available 
for   cultivation.     The   flow   of    the   rivers   is 
improved  because  the  water  formerly  left  to 
soak  through  the  land  is  carried  at  once  to 
the  rivers  either  by  gravitation  or  pumping. 
The    fen    lands    of    Huntingdonshire,    Cam- 


bridgeshire, Lincolnshire,  and  elsewhere,  have 
by  draining  been  made  habitable  and  healthy, 
and  many  thousands  of  acres  have  been 
brought  into  cultivation.  The  natural  drain- 
age of  land  is  by  means  of  ridge-furrows, 


S 'pipes  may  be  La/a/  round  edge 
of  site    w/th    stoneware    bends  at 
arxyies 


/2'.€*  beLotY  surface 
or  excavated  site 


Drains  Co  be  Laid 
Cowards  Lowest  s/de. 
If  very  wet  Lay 
i'.O" 'deeper.  . 
Site  of  bu/Ldtnq 
Co  be  covered  w/th 
6" of  cement  concrete 


Pia/n    earthenware 
p/pes    '/z"  space 
between   ena/s 


-S/o  trees  to  be 
planted  on 
this   area 


<rface 


•41/2  brick    catchpit 

for  seof/menf 
brought  Co  -surface 
with   manhole  cover 


CaCchpit  for 
fntercept/ng      sed/menc 
Crap 


«—  4  socketed  cesnesiC 
jo/nted  p//oe 


Ditch     or   sewer     or    fire    reservoir 

Drainage    to   term/note  in  a  well-  and  purryo  /'f 
sto  o/itch    or  •sewer    or  -stsiCarble     outlet 

FlG.  1. — Plan  of  Drams. 

ditches,  watercourses,  streams  and  rivers ; 
this  is  effective  for  ordinary  soils  and  circum- 
stances, but  in  certain  situations  pipe-draining 
is  necessary.  Shallow  drains  for  clay  soils 
consist  of  2  in.  field  pipes,  from  18  in.  to 
2  ft.  deep,  and  10  to  20  ft.  apart,  laid  with  the 
fall  of  the  land,  or  about  1  in  150,  to  the 


457 


SUB 


ENCYCLOPEDIA   OF 


SUB 


nearest  ditch  or  watercourse,  or  to  dry  steined 
wells  or  to  "  soak-aways "  if  there  is  no 
natural  outlet.  A  soak-away  is  a  square  pit 
sunk  in  the  ground  and  filled  with  rubble  or 
brick-bats  to  admit  water  freely  and  let  it 


Upper   end   of 


PIG.  2. — Section  through  Upper  End 
of  Drain. 

soak  away  gradually.  For  light  and  porous 
soils  deep  drains  are  desirable,  say  from  3  in. 
to  4  in.  diameter,  3  ft.  6  in.  to  6  ft.  deep  and 
half  a  chain  to  a  chain  (33  ft.  to  66  ft.)  apart. 


FIG.  3. — Section  through  Lower  End 
of  Drain. 

In  the  heavy  lands  of  Norfolk  the  drains 
which  answer  best  are  2^  ft.  deep  and  one- 
third  of  a  chain  (22  ft.)  apart.  Land  planted 
with  trees  can  only  be  drained  by  open  cuts, 
as  the  roots  would  inevitably  choke  pipe 


drains.  Drain  pipes  should  not  be  less  than 
20  ft.  away  from  growing  timber.  When  a 
house  has  to  be  erected  on  a  wet  site  the  sub-- 
soil  should  be  drained  by  agricultural  pipes 
covered  with  brushwood  or  rubble  to  prevent 
the  clogging  of  the  pipes  by  the  soil  being 
carried  down.  Fig.  1  shows  the  plan  of  such 
drains,  Fig.  2  section  through  the  upper  end 


toot 


FIG.  4. — Trenching  Tool. 

of  drain,  Fig.  3  section  through  lower  end  of 
drain,  Fig.  4  a  trenching  tool  or  spade,  Fig.  5 
a  bent  iron  rod  for  laying  the  pipes  in 
position.  In  open  country,  if  the  ground  falls 
towards  the  house  and  brings  down  much 
water,  a  deep  trench  or  ditch  about  10  yds. 
away  from  it  on  the  upper  side  will  intercept 


FIG.  5. — Iron  Rod  for  Laying  Pipes. 

much  of  the  water,  and  the  cutting  may  if 
desired  be  filled  in  as  a  rubble  drain  or  pipe 
drain  with  a  deeper  soak-away  at  each  end. 
Where  it  is  practicable  it  is  often  better  to 
make  the  ditch  or  trench  all  round  the  house 
so  as  to  draw  away  the  moisture  from  beneath 
the  footings  and  leave  the  foundation  soil 
undisturbed.  H.  A. 


458 


sue 


MUNICIPAL  AND   SANITAEY  ENGINEEBING. 


SUR 


Suction  of  Pumps. — In  the  installation  of 
a  pumping  plant  every  effort  should  be  made 
to  keep  the  suction  of  the  pump  as  short  as 
possible.  All  pumps  work  most  smoothly  with 
the  water  almost  gravitating  into  the  pump. 
The  weight  of  the  atmosphere  (14'7  Ibs.  to  the 
square  inch)  will  balance  a  column  of  water 
34  ft.  in  height,  but  in  order  to  attain  this 
depth  of  suction  the  pump  must  be  absolutely 
perfect  and  capable  of  maintaining  a  complete 
vacuum.  Such  conditions  are  impossible  to 
attain  in  practice,  and,  as  mentioned  above, 
the  shorter  the  suction  lift  the  better  will  be 
the  working  of  the  pump.  Too  long  a  suction 
is  a  frequent  cause  of  trouble  in  the  working 
of  pumping  machinery.  It  often  happens 
that  such  a  pump  will  not  fill,  and,  upon  the 
return  stroke,  the  piston  meets  the  rising 
column  of  water  with  a  violent  blow  liable  to 
cause  considerable  damage.  Long  suctions 
are  especially  unsuited  for  high-speed  pumps, 
and  it  may  be  taken  as  a  rule  that  the  greater 
the  speed  of  the  pump,  the  shorter  should  be 
the  suction.  Horizontal  length  of  suction  is 
not  so  detrimental  to  the  action  of  a  pump  as 
is  excess  of  vertical  height,  but  it  should  be 
avoided  as  far  as  possible,  as  it  greatly 
increases  the  weight  of  water  to  be  set  in 
motion  and  stopped  at  each  stroke,  or  at  any 
rate  alternately  accelerated  and  retarded. 
With  a  vertical  engine  the  arrangement  of 
the  suction  is  conveniently  managed,  as  in 
this  case  the  pumps  are  usually  fixed  below 
the  engine-room  floor  level  and  within  easy 
reach  of  the  water  to  be  raised.  Correspond- 
ing facilities  do  not  apply  in  the  case  of 
the  horizontal  type  of  engine.  "  Three- 
throw"  pumps,  as  conveniently  worked  from 
a  crank-shaft  of  a  triple-cylinder  engine,  have 
the  advantage  that  the  flow  of  water  in  the 
suction,  and  also  of  course  in  the  delivery 
pipes,  is  more  uniformly  maintained  than  in 
other  forms.  All  suction  pipes  should  be  as 
straight  as  possible,  any  unavoidable  bends 
being  made  of  large  radius ;  the  suction 
should  also  be  perfectly  air-tight,  and  be 
provided  with  foot  or  retaining  valves, 
especially  in  long  suctions  or  heavy  lifts, 


so  as  to  keep  the  pump  ready  charged  with 
water.  The  suction  must  be  of  larger 
diameter  than  the  delivery,  and  additional 
diameter  allowed  if  of  great  length.  Strainers, 
with  ample  area  of  strainer-holes,  should 
be  fitted  at  the  end  of  the  suction  to  ex- 
clude foreign  matters.  At  any  unavoidable 
bends  or  possible  air  lodges  in  the  suction 
pipe,  air-cocks  should  be  provided  for  the 
purpose  of  discharging  the  air  and  preventing 
"air-locking."  W.  H.  M. 

Surface  Traps,    ("  See  GULLIES.") 

Surveying,  General   Principles    of.— 

Chain  Surveying — Angle  Measuring  Instru- 
ments —  Theodolite  —  Ordnance  Survey. — The 
fundamental  process  of  surveying  consists  in 
setting  out  upon  the  area  to  be  mapped  a 
series  of  lines  to  form  a  basis  of  measurement. 
CHAIN  SURVEYING. — In  "chain"  survey- 
ing, all  the  lines  are  measured,  and  as  the 
angles  of  a  three-sided  figure  can  be  deter- 
mined if  the  sides  are  known,  angle  measuring 
instruments  are  not  essential,  although  it  is 
often  convenient  to  employ  the  simpler  forms. 
A  simple  survey  of  open  accessible  country 
can  usually  be  made  with  a  chain,  a  tape,  10 
arrows,  1  doz.  ranging  poles,  some  pegs, 
&c.,  and  a  "  field-book  "  in  which  to  enter  the 
measurements  and  sketches  taken  on  the 
ground.  Extensive  and  more  complicated 
surveys  are  carried  out  upon  the  trigono- 
metrical principle  that  if  the  length  of  one 
side  of  a  triangle  and  the  angles  included 
between  this  side  and  the  others  are  known, 
the  lengths  of  the  remaining  sides  may  be 
calculated.  To  conduct  a  "trigonometrical" 
survey  a  theodolite  for  measuring  the  angles 
will  be  required  in  addition  to  the  apparatus 
used  in  chain  surveying.  The  chain  (Gunter's) 
generally  used  in  surveying  is  composed  of  100 
steel  wire  links,  each  measuring  7'92  in.  from 
centre  to  centre;  the  total  length  (including 
the  handles)  is,  therefore,  66  ft.  As  the 
statute  acre  contains  10  square  chains,  cal- 
culations of  area  are  simplified  by  adopting  a 
chain  of  this  length  and  division.  In  some 


459 


SUE 


ENCYCLOPEDIA  OF 


SUR 


cases,  however,  such  as  for  town  work  and 
levelling,  a  chain  with  100  divisions  of  a  foot 
is  more  convenient.  The  tape  is  of  linen  or 
steel ;  one  side  is  divided  into  links,  the  other 
into  feet  and  inches  ;  a  usual  length  is  66  ft. 
Before  commencing  each  day's  work  both 
chain  and  tape  should  be  tested  between 


FIG.  l. 

gauge  marks  set  out  upon  a  level  surface  ; 
this  is  imperative  when  the  survey  is  being 
made  for  legal  purposes.  Arrows  are  merely 
stout  steel  skewers  about  15  in.  long,  with 
a  small  piece  of  red  cloth  attached  to  each  to 
render  them  easily  distinguishable ;  they  are 
used  to  temporarily  mark  the  number  of  chain 
lengths.  The  ranging  poles  are  from  6  ft. 
to  10  ft.  long,  and  are  painted  in  alternate 
bands  of  black  or  red  and  white  ;  they  are  shod 
with  steel,  and  sometimes  have  small  flags 
tied  to  them.  A  10-link  "offset  staff"  is 
often  used  for  taking  measurements  on  either 
side  of  the  chain,  but  it  is  not  indispensable, 
as  this  can  be  done  with  a  ranging  pole.  The 
field-book  is  about  8  in.  by  4  in.  and  opens 
lengthwise ;  each  page  is  divided  in  the 
direction  of  its  length  by  a  central  line 
(sometimes  two  parallel  lines)  which  repre- 


sents the  chain  line  ;  upon  it  the  distances  on 
the  chain  are  recorded  and  also  the  points  at 
which  offsets  are  taken,  roads  crossed,  &c. 
To  either  side  of  this  line  (or  lines)  the  distances 
to  objects  on  the  right  or  left  of  the  chain 
line  ("  offsets ")  are  entered  and  sketches 
made  of  fences,  buildings,  &c.,  together  with 
any  other  notes  that  may  be  required.  Each 
chain  line  is  started  from  the  bottom  of  a  fresh 
page,  working  from  the  end  of  the  book.  At 
the  commencement  of  a  survey  a  reconnoitre 
of  the  ground  is  made  and  the  principal  lines 
ranged  out  with  the  poles.  These  lines  should 
lie  as  near  boundaries  and  other  main  features 
as  possible  in  order  that  the  offsets  may  not 
exceed  about  50  links.  Besides  these  lines, 
others,  known  as  "proof"  or  "tie"  lines, 
must  be  established  as  a  check.  The  survey 
lines  thus  set  out  should  be  marked  on  a 
rough  plan.  The  ends  of  the  lines  and  their 
junctions  with  others  constitute  "  stations  "; 
the  latter  are  marked  on  the  ground  with  pegs 
or  poles,  and  in  the  field-book  by  a  small  oval. 


FIG.  2. 

Fig.  1  represents  an  area  lined  out  in  the 
manner  aforesaid.  It  will  be  noticed  that  the 
lines  divide  it  into  a  series  of  triangles  ;  these 
are  purposely  made  as  nearly  equilateral  as 
possible.  The  actual  work  of  ranging  and 
chaining  cannot  well  be  explained  here ;  suffice 
it  to  say  that  the  line  must  lie  absolutely 
straight  between  the  stations.  The  arrows  are 


460 


SUR 


MUNICIPAL  AND   SANITAEY  ENGINEERING. 


SUR 


put  down  by  the  "  leader  "  and  withdrawn  by 
the  "follower";  thus  the  number  of  chain 
lengths  may  be  easily  counted.  When  the 
follower  has  acquired  the  10  arrows  an  entry 
is  made  in  the  field-book,  and  the  leader 
retakes  possession  of  them.  As  a  plan  is  the 
horizontal  delineation  of  the  ground  surface, 
all  measurements  taken  upon  an  incline  of, 


say,  more  than  5°  must  be  reduced  to  their 
horizontal  value.  If  the  slope  is  not  very 
steep  this  can  be  accomplished  by  holding  the 
chain,  or  a  portion  of  it,  horizontally  and 
marking  the  distance  with  a  pole  placed 
vertically,  or  preferably  a  plumb-bob ;  this  is 
known  as  "  stepping."  Another  method  is  to 
calculate  the  horizontal  distance  from  the 
angle  of  the  slope.  It  frequently  happens 
that  a  chain  line  is  interrupted  by  some 
obstacle  such  as  a  river  or  a  building.  In  the 
former  case,  if  A  B  (Fig.  2)  is  the  line,  and 
the  river  is  too  wide  to  chain  across,  but  the 
distance  B  C  is  required,  range  point  C  in  line 
with  A  B  and  set  out  perpendiculars  A  D,  B  E, 
range  E  with  C  D,  then : — 


B  C  = 


A  B  X  B  E 
AD  -  B  E' 


If  the  obstacle  interferes  with  the  line  of 
sight,  the  chain  line  may  be  continued  by 
setting  out  A  C,  B  D  (Fig.  3)  perpendicular 
to  A  B  and  equal  to  each  other,  and  ranging 
E  F  with  C  D  and  erecting  perpendiculars 
equal  to  A  C  and  B  D  at  E  G  and  F  H.  A 
perpendicular  is  best  set  out  with  some 
angular  instrument,  such  as  an  optical 
square,  but  it  may  be  done  with  80  links  of 
the  chain  by  placing  arrows  40  links  apart  on 
the  chain  line,  as  a  base,  and  forming  the 
hypotenuse  and  perpendicular  of  a  triangle 
with  50  and  30  links  respectively  (see  Fig.  4). 
Fig.  5  represents  a  chain  survey  of  a  small 
estate ;  the  pages  of  the  field-book  correspond- 


ing thereto  are  shown  by  figures.  In  plotting 
the  work  on  paper  the  chain  lines  and  stations 
are  first  laid  down  and  checked  by  the  tie 
lines,  the  detail  being  afterwards  added.  This 
drawing  would  be  kept  for  reference  and  a 
tracing  or  copy,  omitting  the  survey  lines, 
made  from  it.  The  compass  point,  corrected 
to  the  true  meridian,  is  always  inserted. 

ANGLE  MEASURING  INSTRUMENTS.  —  To 
adequately  describe  the  many  instruments 
used  in  surveying  would  need  a  treatise  ;  only 
the  more  important  ones  can  here  be  mentioned 
and  their  chief  uses  indicated. 

The  optical  square  has  already  been  alluded 
to  ;  it  is  an  inexpensive  pocket  instrument  by 
which  right  angles  may  be  set  out.  This  is 
sometimes  done,  but  not  so  reliably,  with  the 
cross  staff.  The  angle  of  a  line  with  the 
magnetic  meridian  may  be  observed  with  a 
prismatic  compass,  another  pocket  instrument. 
It  is  often  used  for  filling  in  the  detail  work  of 
a  large  survey.  The  box  sextant  is  equally 
portable,  but  capable  of  a  nicer  adjustment; 
angles  in  a  vertical,  as  weir" 
as  a  horizontal,  plane  can 
be  determined  by  it.  Of  all 
angular  measuring  instru- 
ments, the  theodolite  is  the 
most  important.  It  consists 
of  a  telescope  (similar  to 
that  of  a  "  dumpy  "  level, 
except  that  the  diaphragm 
markings  are  different) 
which  may  be  moved 
through  vertical  and  hori- 
zontal planes.  Means  are 
provided  for  closely 
measuring  the  angular 
movement  of  the  optical 
axis  of  the  telescope; 
spirit-levels  and  a  compass  are  also  fitted. 
The  bearings  of  two  lines  from  the  observer's 
station  to  two  distant  points,  one  with  the 
other,  either  in  a  vertical  or  horizontal 
plane,  may  therefore  be  taken  with  great 
exactitude.  The  relation  of  a  horizontal  line 
with  the  magnetic  meridian  can  also  be 
ascertained. 


FIG.  4. 


461 


SUR 


ENCYCLOPAEDIA  OF 


SUR 


SURVEYING  WITH  THE  THEODOLITE. — Many  ascertained  with  great  accuracy  by  the  use  of 
surveys  would  be  extremely  tedious  and  diffi-  the  theodolite,  the  number  of  check  lines  may 
cult,  and  even  impossible,  without  the  theodo-  be  reduced.  With  the  theodolite  the  principles 


1058 


Lin 


30     35 


Lin 


Un 


e  6 


6*5 
6<o 


170 


-i\o  6»6 


\o  6.  5 


10  60 


iQ.**-^!? 


45C25 


Lin 


L>r\e1 


o  4 


20 


FIG.  5. 


lite  or  its  equivalent.  The  long  lines  of  of  trigonometry  can  be  applied  to  determine 
extensive  surveys,  especially  when  over  undu-  the  position  and  distance  of  various  points  and 
lating  ground,  are  best  set  out  with  it.  As  the  height  of  inaccessible  objects.  In  trigo- 
the  angular  bearing  of  these  lines  can  be  nometrical  surveying  a  suitable  base  line  and 

462 


SUR 


MUNICIPAL  AND   SANITARY  ENGINEERING. 


TAP 


the  principal  stations  are  carefully  chosen  and 
the  ground  triangulated  as  in  chain  surveying. 
The  stations  at  the  extremities  of  the  base  line 
need  not  necessarily  be  visible  from  one 
another,  but  it  should  be  possible  to  observe 
them  easily  from  the  surrounding  country. 
As  the  system  of  triangulation  is  built  upon 
the  base  line,  it  is  necessary  to  measure  it 
with  the  greatest  care ;  in  important  surveys 
this  is  usually  done  twice.  If  required,  a  base 
line  can  be  extended  by  angular  measurement 
from  suitable  points.  Although  the  length  of 
the  sides  of  a  triangle  may  be  calculated  if  the 
base  and  the  angles  included  by  it  and  the 
sides  are  known,  it  is  necessary  to  measure  at 
least  one  of  the  distant  sides  of  the  triangula- 
tion as  a  check.  After  the  main  system  has 
been  established  it  is  subdivided  into  smaller 
triangles  and  the  details  worked  out  as  in 
chain  surveying.  Lakes,  marshes,  woods,  &c., 
may  be  surveyed  by  inclosing  them  in  a 
system  of  lines  and  observing  the  angles  that 
these  lines  make  with  each  other.  As  the 
sum  of  the  interior  angles  should  be  equal  to 
90°  multiplied  by  twice  the  number  of  sides 
that  the  figure  formed  by  the  lines  contains, 
less  360°,  a  proof  of  their  accuracy  may  be 
established.  If,  in  plotting  the  work,  the  first 
and  last  lines  do  not  meet,  there  is  an  error 
in  the  lineal  measurement.  This  method  of 
surveying  is  known  as  a  "  closed  traverse." 
If  done  with  a  chain  it  would  generally  be 
necessary,  owing  to  the  difficulty  in  taking 
diagonals,  to  prolong  the  lines  and  so  form 
exterior  angles,  checking  the  same  with  tie 
lines.  The  courses  of  winding  roads,  rivers, 
&c.,  are  also  "  traversed  " ;  this  again  can  be 
more  accurately  and  expeditiously  accom- 
plished with  the  theodolite  than  by  the  chain. 
The  line  of  traverse,  along  the  road  or  the 
bank  of  the  river,  is  usually  arranged  to  start 
from  a  definitely  fixed  point  in  the  general 
survey  and  finish  on  another.  In  some  cases 
the  angles  of  the  various  sections  of  the  line 
are  determined  in  relation  to  the  magnetic 
meridian.  When  extreme  accuracy  is  not 
essential  this  may  be  done  with  the  prismatic 
compass.  In  town  surveying  the  shape  of  the 


streets  precludes  triangulation,  so  that  the 
angles  of  the  survey  lines  must  be  measured. 
To  obtain  a  sufficiently  long  base  line  is  often 
a  matter  of  considerable  difficulty  ;  in  some 
cases  a  space  outside  the  town  is  selected  for 
this. 

THE  ORDNANCE  SURVEY. — The  whole  of 
Great  Britain  has  been  most  elaborately  sur- 
veyed, and  maps  to  the  following  scales  are 
published  by  the  Ordnance  Survey  Depart- 
ment. These  may  be  obtained  in  London 
through  the  appointed  agent,  Mr.  Edward 
Stanford,  of  12  to  14,  Long  Acre,  W.C. 


Natural 

Inches  to  One 

Natural 

Inches  to  One 

Scale. 

Mile. 

Scale. 

Mile. 

•500 

126-720 

2T&JO 

25-344 

~528 

120-0 

TCT5FO 

6-0 

TO51J 

60-0 

1 
6TJ36O 

1-0 

Besides  the  above,  four  smaller  scales  are 
also  used. 

^Joth  Scale. — Most  of  the  towns  of  Great 
Britain  have  been  published  to  this  scale, 
which  generally  shows  hydrants,  lamp-posts, 
manholes,  &c.,  besides  the  thickness  of  walls, 
spaces  between  buildings,  &c. 

TOLgth  Scale. — The  plans  of  London,  Dublin, 
Belfast,  and  some  small  towns  are  on  this 
scale. 

^ooth  Scale. — The  whole  of  the  cultivated 
districts  of  Great  Britain  (Ireland  is  in  pro- 
gress) are  obtainable  on  this  scale,  which 
shows  woods,  rough  pasture,  rocks,  &c.,  in 
character.  The  acreage  of  fields  and  levels  of 
bench  marks  are  included  in  the  later 
editions. 

loib^th  Scale. — Maps  to  this  scale  have 
generally  the  same  detail  as  the  ^ooth,  but 
they  do  not  give  areas  or  parcel  numbers. 

g-^goth  Scale. — This  is  the  general  road 
map  of  the  country.  In  addition  to  the  above, 
maps  of  the  Geological  Survey  of  England 
and  Wales  may  be  obtained.  (See  "  LEVELLING, 
GENERAL  PRINCIPLES  OF.")  E.  L.  B. 


Taps.     (See  "VALVES.") 


463 


TES 


ENCYCLOPEDIA  OF 


TES 


Testing  Apparatus. — DRAIN  PLUGS.— 
Made  of  various  patterns,  these  are  all  con- 
structed on  the  same  principle.  They  consist 
of  two  metal  discs — one  fixed  to  and  the  other 
passed  over  a  screwed  spindle — between  which 
rests  an  indiarubber  ring.  By  screwing  up  a 
fly-nut  on  the  spindle  the  two  plates  are 
pressed  together  and  the  rubber  ring  expanded 
and  forced  out  against  the  periphery  of  the 
drain,  which  is  thereby  plugged.  In  the 
majority  of  plugs  the  spindle  is  hollow  and 
fitted  with  a  cap.  This  allows  of  the  attach- 
ment of  the  nozzle  of  a  smoke  machine,  and 
is  useful  for  the  gradual  emptying  of  a  drain 
after  testing  with  water  when  the  pressure  is 
high. 

DRAIN  BAGS. — India-rubber  or  waterproofed 
canvas  bladders,  which,  when  inserted  in  a 
drain  to  be  plugged,  are  inflated  by  means  of 
a  small  air-pump.  They  adapt  themselves 
better  to  any  unevenness  in  the  shape  of  the 
drain  than  do  drain  plugs. 

SMOKE  MACHINES. — Utilised  for  the  genera- 
tion of  smoke  used  in  drain-testing.  They 
are  made  of  various  patterns,  but  consist 
generally  of  a  combustion  chamber  and  a 
pump,  fan,  or  bellows  for  forcing  the  smoke 
into  the  drains.  Smoke  is  produced  by  burn- 
ing oiled  cotton  waste  or  "  touch  paper," 
which  latter  is  specially  prepared  brown  paper. 
The  machines  are  provided  with  a  length  of 
tubing  for  connecting  up  to  the  drains. 

SMOKE  SOCKETS  OR  SMOKE  CASES. — Cylin- 
drical cardboard  cases  about  7  in.  long  and 
2  in.  in  diameter  filled  with  a  compound 
which  on  ignition  generates  dense  volumes  of 
smoke.  Two  strips  of  wood  are  attached, 
which,  when  spread  out,  keep  the  rocket  off 
the  invert  of  the  drain. 

SMELL  TESTERS. — Made  in  many  varieties. 
Consist  of  small  tubes  filled  with  assafcetida 
or  other  strong-smelling  compound,  closed  by 
caps  which  are  held  down  by  paper.  When 
passed  into  the  drains  the  paper  is  wetted  and 
thereby  softened  and  broken,  allowing  the 
contents  of  the  tubes  to  be  discharged  in  the 
drains.  Water  being  thrown  into  the  drainage 
system,  the  chemical  is  passed  to  all  parts  of 


the  drains,  which  it  charges  with  its  distinctive 
smell. 

Testing  Drains. — The  two  most  reliable 
tests  made  use  of  for  proving  the  soundness  of 
drains  are  the  hydraulic  or  "  water  "  test  and 
the  pneumatic  or  "  air  "  test.     The  former  is 
applied  by  securely  plugging  the  outlet  end  of 
the  drain  (or  system  of  drainage)  and  filling 
up  the  piping  with  water.     When  the  drain  is 
full,  the  water  level  is  carefully  marked  and 
watched  for,  say,  half  an  hour.     If  it  remains 
stationary,  the  drain  is  proved  sound,  in  the 
opposite  event  a  leakage  exists.     In  applying 
the  pneumatic  test,  all  openings  on  the  drain- 
age system  or  of  a  section  thereof — such  as 
gullies,  closets,  vent-pipes,  &c. — are  carefully 
sealed  and  air  pumped  into  the  drains.      The 
pressure   attained   is   indicated   on   a    gauge 
(which  may  simply  consist  of  a  U-shaped  glass 
tube  charged  with  water)  attached  to  a  plug 
closing  one  of  the  openings  in  the  drain.     The 
gauge  being  carefully  watched  after  the  desired 
pressure  has  been  obtained,  the  soundness  or 
leaking  conditions  of   the   drains  under   test 
will   be   indicated   by   the   constancy   or   the 
diminution   in    pressure    respectively.      The 
pneumatic  test  in  drainage  work  is  superior  to 
the   water   test  in   that,   in   the  former,  the 
pressure  applied  is  of  uniform  severity  on  each 
part  of  the  drainage  system,  whereas  it  varies 
greatly  in  intensity  in  the  case  of  the  water 
test ;  the  lower  portion  of  the  drain  having  to 
withstand    a    much    greater   pressure  under 
this   test  than   the   upper   end.      The   other 
tests  made  use  of  in  drainage   work  are  the 
"  smoke  "    test    and   the    "  olfactory  "    tests. 
The  former  is  valuable  in  that  the  positions  of 
leakages  are  at  once  made  apparent  by  the 
escape  of  smoke  from  the  drains  at  the  defec- 
tive  points.     If   the   test    is    applied    under 
pressure   it   is   as   valuable   as   the   air  test. 
Without  pressure,  the  results  are  unreliable, 
as  the  absence   of   escaping  smoke   does  not 
necessarily   imply  that    the   drain  is  sound, 
particularly  if  the  pipes  are  covered  by  earth. 
A   thin  coating  of   sewage  or   grease  over   a 
defect  will  also  prevent  the  escape  of  smoke  if 


464 


THE 


MUNICIPAL  AND   SANITAEY  ENGINEERING. 


THE 


little  or  no  pressure  is  used.  Under  the  smoke 
test,  smoke  generated  in  a  smoke-machine  is 
pumped  into  the  drain  through  a  manhole  or 
other  opening  in  the  drains.  After  the  drain- 
age system  has  been  fully  charged,  all  open- 
ings are  closed  and  pumping  continued  until 
the  test  has  been  completed.  For  convenience 
of  carriage,  "  smoke-rockets  "  are  frequently 
made  use  of  in  preference  to  the  cumbersome 
"  machine,"  but  as  neither  the  quantity  of 
smoke  applied  by  these,  nor  its  movement  in 
the  drains  can  be  controlled,  they  are  of  no 
practical  value  in  the  majority  of  cases. 

Olfactory  tests  consist  in  charging  the 
drains  with  some  pungent  or  otherwise  dis- 
tinctive smell,  that  should  be  detected  at 
points  at  which  defects  exist.  Oil  of  pepper- 
mint mixed  in  a  bucketful  of  hot  water  and 
poured  into  the  drains  is  frequently  made  use 
of;  while  many  proprietary  testers  similarly 
used  are  available.  These  latter  are  prefer- 
able in  that  the  smell  is  not  generated  until 
the  interior  of  the  drain  or  pipe  to  be  tested 
has  been  reached.  While  frequently  useful, 
smell  tests  are  unreliable  and  cannot  be  used 
for  proving  soundness.  G.  J.  G.  J. 

Thermometers. — An  ordinary  thermo- 
meter consists  of  a  fine  glass  tube  with  a  bulb 
blown  on  at  one  end,  and  is  partly  filled  with 
mercury  or  alcohol.  This  liquid  expands  on 
being  heated,  and  contracts  on  being  cooled. 
When  it  expands  it  passes  up  along  the  tube, 
and  by  the  amount  of  this  expansion  the 
temperature  is  measured  by  means  of  a  scale 
marked  off  on  the  tube.  In  this  country 
Fahrenheit's  scale  is  in  general  use.  In  this 
the  freezing  point  is  32°  and  the  boiling  point 
212°,  the  intermediate  part  of  the  scale  being 
divided  into  180  degrees.  In  most  foreign 
countries  the  Centigrade  scale  is  used,  in 
which  the  freezing  point  is  0°  and  the  boiling 
point  100°.  All  good  thermometers  have  the 
scale  etched  on  the  tube,  and  it  is  desirable 
that  they  should  be  verified  at  the  Kew 
Observatory,  so  that  their  errors  may  be 
known  and  allowed  for.  There  are  two 
patterns  of  maximum  thermometer,  viz., 


Negretti  &  Zambra's  and  Phillips's.  In 
Negretti  &  Zambra's  maximum  thermometer 
the  bore  of  the  tube  is  reduced  in  section  near 
the  bulb  in  such  a  way  that  whilst  the  expand- 
ing mercury  forces  itself  into  the  tube,  on 
contraction  the  column  of  mercury  in  the  tube 
breaks  off,  so  that  its  upper  extremity  shows 
the  highest  temperature  that  has  been 
attained.  In  Phillips's  maximum  thermo- 
meter the  index  is  formed  by  a  small  portion 
of  the  mercurial  column,  separated  from  the 
main  thread  by  a  minute  air-bubble;  this 
portion  is  pushed  on  before  the  column  when 
the  temperature  rises,  but  does  not  return 
with  it  when  it  falls.  The  detached  portion 
of  the  column  therefore  rests  at  the  extreme 
position  to  which  it  has  advanced,  and  the  end 
of  it  furthest  from  the  bulb  registers  the 
highest  temperature  which  has  been  attained. 
Both  instruments  are  set  by  holding  them 
bulb  downwards. 

In  the  minimum  thermometer  spirit  is 
employed  instead  of  mercury,  and  in  it  there 
is  immersed  a  pin  or  index.  When  the 
temperature  falls  the  surface  of  the  spirit 
draws  the  index  along  with  it,  but  on  rising 
again  the  spirit  passes  the  index,  leaving  it  at 
the  lowest  point  to  which  it  has  been  drawn, 
the  end  furthest  from  the  bulb  thus  registering 
the  minimum  temperature.  The  instrument 
is  set  by  raising  the  bulb  and  allowing  the 
index  to  slide  to  the  end  of  the  column  of 
spirit.  The  instruments  used  for  measuring 
the  amount  of  moisture  present  in  the  air  are 
the  dry-bulb  and  wet-bulb  thermometers. 
The  dry-bulb  is  an  ordinary  thermometer,  and 
shows  the  temperature  of  the  air ;  the  wet- 
bulb  is  a  precisely  similar  thermometer  only 
it  has  the  bulb  covered  with  a  piece  of  muslin, 
which  is  kept  wet  by  a  conducting  thread 
passing  into  a  vessel  of  water.  If  the  air  is 
dry  it  evaporates  the  moisture  from  the  damp 
muslin,  and  in  doing  so  lowers  the  tempera- 
ture, and  consequently  this  thermometer  reads 
lower  than  the  dry-bulb. 

For  meteorological  and  comparative  pur- 
poses the  dry-bulb,  wet-bulb,  maximum  and 
minimum  thermometers  should  be  mounted 


M.S.E. 


465 


H  H 


TID 


ENCYCLOPEDIA   OF 


TID 


in  a  Stevenson  screen,  which  is  a  louvre- 
boarded  box,  with  their  bulbs  4  ft.  above 
the  ground.  Other  thermometers  in  use  at 
meteorological  stations  are  earth  thermo- 
meters, for  ascertaining  the  temperature  of 
the  soil  (the  most  suitable  depths  are  1  ft., 
2  ft.,  and  4  ft.);  sensitive  minimum  ther- 
mometer on  grass,  for  determining  the 
intensity  of  terrestrial  radiation  at  night ; 
black-bulb  and  bright-bulb  maximum  ther- 
mometers in  vacua,  for  determining  the 
intensity  of  solar  radiation.  Much  interesting 
and  valuable  information  may  be  obtained 
from  a  self-recording  thermometer,  such  as 
the  Eichard  thermograph.  W.  M. 

Tidal  Valves. — Comparatively  heavy  metal 
flaps  fixed  on  the  outlet  ends  of  drains  dis- 
charging into  tidal  waters,  streams  liable  to 


Tidal  Valve. 

flooding,  and  in  similar  positions.  The  flaps 
are  hinged  to  the  crowns  of  the  pipes  in  such 
a  way  that  water  or  sewage  passing  through 
the  drains  will  raise  them  and  issue,  while  a 
reverse  movement  of  water  (caused  by  high 
tides,  &c.)  will  exert  a  pressure  on  the  valves 
and  close  them  tightly  against  the  mouths  of 
the  pipes  ;  thereby  preventing  the  backing-up 
of  water  into  the  drains. 

Tides   on   Sewer  Outfalls,  The  effect 

of. — The  majority  of  towns  situated  on 
the  sea-coast  are  sewered  with  one  or  more 
outfalls  into  the  sea.  In  selecting  the  positions 
for  these  outfalls,  due  attention  must  be  given 
to  tidal  currents,  and  experiments  and  obser- 
vations are  necessary  to  determine  the  direction 


of  flow,  the  effect  of  prevailing  and  other  winds, 
the  rise  and  fall  of  the  tide,  and  the  conditions 
of  the  sea  bed,  whether  suitable  or  otherwise 
for  outfall  purposes.     The  engineer  should  be 
acquainted  with  the  peculiarities  of  the  subject 
of  coast   work    and    conditions   appurtenant 
thereto.     The  question  of   tidal  rivers  must 
also  enter  into  the  category,  having  regard 
to    their   tendency   to   silt   up    the    adjacent 
sea  bed.     Tidal    rivers,  however,    frequently 
afford   an   advantage   in  discharging  sewage, 
as  the  tide  ebbs  for  a  longer  period  than  it 
flows.     Great  care  should  be  taken  to  avoid 
an  eddy  current,  which  is  common   in  some 
situations.      Those   tides   or   currents   which 
have  a  circular  movement  will  frequently  pre- 
vent the  effectual  removal  of  the  sewage,  and 
cause  it  to  be  deposited  on  the  shore.     Sea 
outfalls  should  not  be  constructed  to  discharge 
against  sea  currents  unless  unavoidable.    The 
chief  disadvantage  in  so  doing  is  that  the  dis- 
charge is  impeded,  whilst  by  adopting  direc- 
tions which  are  parallel  with  the  currents,  the 
flow  in  the  outfall  will  frequently  be  consider- 
ably accelerated.     Attention  should  be  paid  to 
the  relative  position  of   outfalls,  with  regard 
to  the  situation  of   towns,  care  being  taken 
that  the  sewage,  after  being  discharged  into 
the  sea,  does  not  flow  in  front  of  the  thickly 
inhabited  parts    of    the    district.     It    should 
rather  be  carried  directly  away  from  all  town 
beaches  and  seaside  attractions.     Inattention 
to  this  important  consideration  may  result  in 
destroying    the    chief    attractions    of    many 
places,    by  rendering  their   bathing   beaches 
insanitary.     One  of  the  most  important  ques- 
tions requiring  attention  is  that  of   the   rise 
and  fall  of  the  tide.     This  must  be  accurately 
ascertained,  and  taken  into  consideration,  in 
conjunction  with  the  survey  of  the  district  to 
be  drained.     It  will  then  be  seen  whether  or 
not  an  outfall  site  can  be  secured,  by  which 
the   sewage   will   all   flow   and   discharge  by 
gravitation,    or   whether    pumping    or  other 
means  will  have  to  be  resorted  to.     Although 
spring  tides  rise  to  a  higher  level  than  neap 
tides,  the  engineer  often  has  greater  difficulty 
in  effecting  a  good  outfall  on  the  neap  tides. 


466 


TID 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


TOW 


Spring  tides  present  not  only  the  highest,  but     outside.     In  constructing  outfalls,  particular 


also  the  lowest  tide  levels,  but  the  reverse 
obtains  in  the  case  of  neap  tides,  as  these 
neither  ebb  so  low  nor  flow  so  high,  and 
therefore  the  sewer  outfall  is  partially  ob- 
structed during  this  latter  period.  The  dis- 
charge chart  must  be  calculated  on  the 
difference  of  head  of  water  within  the  sewer 
and  over  it  during  neap  tides,  having  due 
regard  to  the  influences  of  prevailing  winds, 
which  will  in  some  situations  have  consider- 
able effect  in  checking  the  flow  of  the  tide.  In 
a  large  number  of  cases  where  a  gravitating  out- 
fall cannot  be  provided  on  account  of  insuffi- 
cient levels,  a  system  of  storage  can  be  adopted 
to  meet  the  requirements  of  the  district, 
avoiding  the  initial  and  working  costs  of  a 
pumping  plant.  If  it  can  be  so  arranged,  the 
outfall  should  be  placed  in  such  a  position  as 
will  allow  a  combined  system  of  storage  and 
gravitation  as  designed  and  carried  out  by  the 
writer  for  the  West  Penwith  District  Council. 
In  this  case  the  outfall  was  carried  diagonally 
under  the  foreshore,  to  a  discharging  point 
beyond  the  boundary,  and  in  the  favourable 
direction  of  the  currents  and  prevailing  winds. 
The  sewers  from  both  the  high  and  low  levels 
were  by  this  means  caused  to  converge  to- 
wards a  central  point,  and  whilst  the  sewage 
from  the  lower  district  was  impounded  at  cer- 
tain periods  of  the  tides,  that  from  the  higher 
levels  discharged  through  the  one  outfall  pipe, 
common  to  both  districts,  continuously.  It 
was  found  necessary  to  store  one-third  of  the 
combined  sewage  and  rainfall  from  the  low 
level  district  on  each  tide.  A  tank  sewer  was 
constructed  for  this  purpose,  having  a  pen- 
stock and  valve  chamber  with  midfeather,  at 
the  outfall  end.  The  main  sewer  for  the  high 
levels  was  terminated  in  the  outer  chamber, 
and,  on  account  of  its  greater  head,  discharged 
through  the  outfall  pipe  at  all  states  of  the 
tide,  whilst  the  low  level  remained  locked  back 
by  self-acthig  balance  valves,  fitted  on  the 
niidfeather  and  chamber,  for  the  purpose  of 
shutting  out  the  tides  until  such  times  as  the 
valves  were  freed  and  the  sewage  released 
by  the  inside  pressure  overcoming  that  on  the 


attention  should  be  directed  to  the  foundation 
upon  which  the  pipes  are  to  be  carried  to  pre- 
vent the  undermining  action  of  the  waves  and 
currents.  F.  L. 

Town  Planning.  —  General  Principles — 
Existing  Powers  —  Example  of  Germany — Zone 
System — Town  Planning  Act — Sweden — Holland 
— Houses  per  Acre — Town  Planning  in  England. 

— Parliament,  and  most  municipal  experts 
now  recognise  how  important  it  is  to  establish 
and  regulate  a  proper  system  of  town  develop- 
ment, which  shall  provide  for  the  organised 
dispersion  of  the  population  of  overcrowded 
centres  to  residential  suburbs,  industrial 
villages  detached  from  the  main  centre,  and 
to  an  agricultural  belt  on  the  outskirts.  The 
developments  that  are  taking  place  in  the 
transmission  of  electric  power  point  to  large 
movements  in  this  direction,  because  they  will 
make  it  possible  not  only  for  industries  to  be 
carried  on  at  distances  from  the  centre,  but 
also  for  such  a  cheapening  and  improvement 
of  the  means  of  transit  for  both  goods  and 
passengers  as  will  tend  to  minimise  the 
obstacles  of  time  and  distance,  which  at  pre- 
sent (though  to  a  less  extent  than  formerly) 
render  it  necessary  to  crowd  factories  and 
population  in  central  districts.  Cheap  tran- 
sit alone,  however,  has  inflicted  on  us  jerry- 
built  suburban  houses  of  the  wrong  type, 
overcrowded  on  area,  and  has  inflated  the 
price  of  land  for  the  benefit  of  the  speculators, 
who  too  often  absorb  the  difference  between 
the  old  rent  paid  on  the  dear  land  in  the  centre 
and  the  true  economic  ground-rent  that  should 
be  paid  for  the  agricultural  land  on  the  out- 
skirts. Hence  it  is  vitally  important  that  the 
control  and  ownership  of  suburban  land 
should  be  more  in  the  hands  of  the  community 
than  at  present,  and  that  one  and  the  same 
authority  should  have  powers  over  transit, 
land,  and  housing,  so  as  to  prevent  the  crea- 
tion of  new  slum  areas  and  excessive  increases 
in  the  cost  of  acquiring  land  for  housing  and 
other  public  purposes  as  well  as  to  provide 
for  open  spaces,  main  roads,  and  streets  of 


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adequate  width  in  the  proper  direction, 
and  in  sufficient  numbers  to  meet  future 
needs,  before  the  land  near  them  is  forced  up 
to  speculative  building  prices.  Town  plan- 
ning is  the  art  of  planning  towns  in  respect  of 
the  distribution  of  buildings  and  open  spaces 
and  the  provision  of  streets  and  roads  suitable 
to  each  area.  It  implies  a  public  authority, 
possessed  of  power  to  control,  guide  and 
regulate  the  growth  and  development  of  towns, 
•especially  as  regards  building  sites,  their 
approaches  and  surroundings. 

EXISTING  POWERS.  —  At  present,  in  the 
United  Kingdom,  the  majority  of  these  matters 
are  settled  by  the  owners  of  the  land,  subject 
to  local  by-laws  applying  practically  the  same 
methods  and  principles  to  all  parts  of  the 
town.  It  is  true  plans  of  "  new  streets  "  must 
be  submitted  to  the  local  authority  for 
approval,  but,  except  in  rare  instances,  no 
such  authority  can  insist  on  a  plan  of  the 
whole  of  a  building  estate  showing  the  rela- 
tions of  the  intended  "new  streets"  to  others 
adjoining.  In  most  towns  there  has  been  no 
power  to  vary  the  direction  or  position  of  the 
streets  shown  on  the  owner's  deposited  plan, 
but  Leeds,  Nottingham,  Barrow-in-Furness, 
Blackburn,  Bournemouth,  Bradford,  and 
Brighton  have  certain  powers  in  this  respect 
subject  to  a  compensation  clause.  The  Public 
Health  Act,  1907,  sections  17  and  22,  makes 
these  powers  general  wherever  the  Act  is 
adopted.  In  a  great  many  towns  the  corpor- 
ation has  obtained  power  by  means  of  a  local 
Act  to  prescribe  a  building  line  subject  to  a 
compensation  clause.  There  are  also  limited 
powers,  varying  considerably  as  between  one 
town  and  another,  for  regulating  the  area  of 
air  space  at  the  side  or  rear  of  dwellings,  from 
a  minimum  of  100  sq.  ft.  in  Bacup  to  a 
minimum  of  500  sq.  ft.  in  Croydon,  but 
the  most  generally  prescribed  area  is  about 
150  sq.  ft.  As  to  width,  streets  are  divided 
into  classes  in  respect  of  which  the  require- 
ments of  towns  vary  considerably.  The 
normal  width  prescribed  is  36  ft.,  but  by  means 
of  local  Acts,  streets  are  classified  in  some 
towns  such  as  Cardiff,  Nottingham,  Leicester, 


Bolton,  Huddersfield,  and  Sunderland,  in 
various  widths,  according  to  their  situation 
and  probable  uses.  Barrow-in-Furness'  local 
Act  prescribes  varying  widths  of  80,  60,  40, 
and  20  ft.,  and  gives  power  to  the  corporation 
at  their  discretion  to  reduce  the  width  of  the 
street  if  an  open  space  is  left  along  one  or 
both  sides  of  the  street,  in  front  of  the 
houses.  Even  when  used  to  their  fullest 
extent,  however,  these  powers  are  inadequate 
to  prevent  the  growth  of  ugly  suburbs  and 
mean  streets,  or  to  secure  for  the  inhabitants 
a  sufficient  supply  of  the  essentials  of  a 
healthy  life  viz.,  sunlight,  fresh  air,  and  vege- 
tation. There  are  at  present  no  statutory 
powers  capable  of  effectively  dealing  with  the 
question  of  town  planning  in  the  United 
Kingdom,  yet  consideration  of  this  subject 
dates  back  at  least  4,000  years,  and  there  are 
numerous  examples  of  what  was  done  in  this 
connection  by  the  Komans  and  Assyrians,  and 
even  in  this  country,  the  town  of  Winchelsea 
was  planned  by  Edward  I.  in  the  Middle  Ages. 
In  Continental  towns,  notably  in  Germany, 
matters  are  more  advanced,  and  although 
many  parts  of  these  towns  are  planned  on 
wrong  lines,  especially  as  regards  the  width 
and  nature  of  streets,  yet  many  of  the  evils 
from  which  our  towns  suffer  have  been 
avoided,  while  the  division  of  building  land 
near  towns  into  plots,  and  the  choice  of  the 
style  of  building  is  regarded  as  the  concern  of 
the  community,  and  one  coherent  official  plan 
is  supplied  by  the  town  councils  to  the  whole 
of  the  unbuilt-on  land  within  the  town  boun- 
daries, deciding  beforehand  the  general  char- 
acter of  building  to  be  allowed  in  the  various 
parts  of  the  area,  according  to  their  antici- 
pated needs.  Mr.  T.  C.  Horsfall  has  done 
much  to  familiarise  us  with  German  experience 
in  this  connection. 

THE  EXAMPLE  OF  GERMANY. — In  Germany, 
town  plans  are  generally  prepared  for  so  large 
an  area  that  "the  needs  of  the  near  future" 
are  provided  for,  and  this  phrase  is  generally 
taken  to  mean  about  25  years.  Dr.  Stubben, 
a  great  German  authority  on  the  subject,  says 
that  the  first  thing  to  be  settled  in  a  town 


468 


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plan  is  the  position,  direction,  and  width  of 
the   principal   streets,    and    this    should    be 
followed  by  a  general  indication  of  the  mode 
of  division  of  the  land  into  sites,  which  must 
be  so  arranged  with  regard  to  each  other  that 
the  demands   of    traffic,    health,   and  beauty 
may  be  complied  with  as  fully  as  possible. 
While   streets   and   open    squares    serve    for 
traffic  it  is  important  so  to  construct  them 
that   they   may   be   of    pleasant  appearance, 
and  this  can  be  gained  by  securing  a  variety 
of    street  forms  and  well    inclosed    squares, 
avoiding  in  all  cases  too  long  straight  lines. 
Principal  traffic  streets  ought  to  be  from  60 
to  120  ft.  wide,   secondary  traffic  streets  40 
to  60  ft.,  sometimes  with  front  gardens,  and 
streets  used  mainly  for  access  to  the  dwellings 
in  them,  25  to  40  ft.,  often  with  front  gardens. 
It  is  this  narrowing  of  the  macadamised  area, 
and  increase  of  the  open  garden  space  that  is 
so  much  needed  in  German  town  planning 
to-day.     Dr.  Mewes,  of  Dusseldorf,  in  laying 
down  the  elements  of  a  town  plan,  urges  that 
there  should  be    a    general  plan,    providing 
for  main  roads  and  transit  facilities,  careful 
grading   of    districts   in  zones  providing  for 
different  types  of  buildings  in  each,  but  with 
one   or   two    districts   for    mixed    buildings ; 
varied  streets  and  open  spaces  ;  reservation  of 
front  gardens  for  future  widening  of  streets  if 
necessary,  and,  as  in  Baden,  Hamburg,  and 
Frankfurt,  plots  belonging  to  different  owners 
should,  where  necessary,   be  pooled  and  re- 
apportioned.     The  law  under  which  this  last- 
named  operation  is  effected  in  Frankfurt  is 
known  as  the  "Lex  Ordickes."     Within  the 
area  covered  by  the  town  plan,  there  should 
be    varied    building    by-laws    providing    for 
restrictions   on   the    extensive    use    of    land 
according  to  its   position,    and   also    on  the 
height   of    buildings,    besides    providing    for 
cheaper  types  of  streets  in  purely  residential 
quarters,    and   relaxed   conditions   as   to  the 
construction  of  buildings. 

ZONE  SYSTEM.  —  An  important  feature  of 
town  planning  is  the  principle  of  dividing 
land  which  is  going  to  be  built  on  into 
different  districts,  each,  or  each  group,  of 


which  has  its  own  building  by-laws.  Under 
this  system  (known  as  the  "  Zone  System  ") 
some  districts  are  reserved  for  factories  and 
works,  other  districts  are  reserved  for  dwell- 
ings, to  the  exclusion  of  factories  and  works, 
while  yet  other  districts  permit  of  a  mixture 
of  the  two  classes  of  buildings.  In  districts 
given  up  to  buildings  near  the  centre  of  the 
town,  five-storey  houses  built  in  rows,  and 
covering  a  large  proportion  of  the  site,  are 
allowed ;  in  other  districts,  the  limit  is  four 
storeys,  and  the  unbuilt-on  area  of  the  site  is 
larger ;  in  other  districts,  no  houses  may  have 
more  than  three  storeys,  while  towards  the 
outskirts,  where  land  is  cheaper,  only  detached 
or  semi-detached  houses  of  two  storeys  are 
permitted,  and  with  a  good  deal  of  land  round 
them,  so  as  to  interfere  as  little  as  possible 
with  the  supply  of  air  passing  towards  the 
central  districts. 

In  Germany,  nearly  all  town  councils  of 
important  towns,  after  having  plans  prepared 
by  their  own  skilled  officials  under  the 
direction  of  a  committee  of  the  town  council 
specially  qualified  for  this  work,  submit  such 
plans  for  revision  to  experts  of  reputation  for 
their  skill  in  suggesting  how  to  make  towns 
convenient  for  traffic  as  well  as  healthy  and 
beautiful.-  When  the  plan  has  received  the 
alterations  that  these  experts  suggest,  it  is  sub- 
mitted to  public  examination,  and  any  citizen 
is  at  liberty  to  make  any  objection  he  likes  to 
any  of  the  proposals.  When  these  alterations 
or  suggestions  have  been  considered,  the  plan 
becomes  law,  with  or  without  the  necessary 
corrections,  and  all  land-owners,  in  developing 
their  estates,  have  to  comply  with  the  direc- 
tions laid  down. 

TOWN  PLANNING  ACT. — The  Town  Planning 
Act  of  1909  was  a  considerable  step  forward  in 
the  housing  legislation  of  the  United  Kingdom. 
By  it  future  developments  will  be  carried  out 
on  quite  a  different  system  to  that  prevailing 
in  the  past.  Town  planning  schemes  may  be 
prepared  by  either  a  local  authority  or  land- 
owners in  respect  to  "any  land  likely  to  be  used 
for  building  purposes  and  of  any  neighbouring 
land."  In  any  such  scheme  provision  shall 


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be  made  for  open  spaces,  roads,  streets,  parks, 
pleasure  or  recreation  grounds,  or  for  any 
work  incidental  to  a  town  planning  scheme, 
whether  in  the  nature  of  building  work  or  not. 
Provision  is  made  for  the  modification  or 
extension  of  any  original  proposals.  The 
approval  of  the  Local  Government  Board  is 
necessary,  and  this  shall  be  published  in  the 
London  Gazette.  Any  objections  must  be 
made  within  twenty-one  days  of  publication, 
and  if  this  is  done,  then  the  draft  order  con- 
firming the  scheme  must  be  laid  before  both 
Houses  of  Parliament  for  thirty  days.  Should 
either  House  present  an  address  against  the 
draft  no  further  proceedings  can  be  taken.  It 
is  important,  however,  not  to  confound  town 
planning  writh  site  planning.  The  former 
deals  with  towns  as  a  whole,  and  includes  all 
the  points  mentioned  in  the  preceding  para- 
graphs relating  to  Germany,  whereas  site 
planning  is  merely  the  planning  of  patches 
of  land  in  one  part  of  a  town,  without 
necessarily  considering  its  relations  to  the 
development  of  the  town  as  a  whole.  While 
eminently  desirable  in  itself,  this  latter  pro- 
cess would  not  meet  the  case  of  municipalities, 
who,  in  the  past,  have  had  to  spend  enormous 
sums  for  widening  streets,  and  may  have  to 
do  so  in  the  future.  In  order  to  ascertain 
how  to  apply  town  planning  to  England  it 
will  be  useful  to  study  the  principles  embodied 
in  the  town  planning  laws  of  other  countries. 
Some  of  the  most  recent  town  planning 
provisions  are  those  contained  in  the  General 
Building  Law  for  the  Kingdom  of  Saxony,  of 
July  1st,  1900,  as  follows  : — "  Local  authori- 
ties must  prepare  a  building  plan  for  all 
unbuilt-on  land,  and  may  prepare  a  plan  for 
a  district  already  built  on."  The  plan  may 
regulate  (1)  the  building  lines  upon  which  the 
sites  may  be  built  on,  and  by  which  the  areas 
intended  for  traffic  or  for  front  gardens  are  to 
be  divided ;  (2)  the  mode  of  building ;  (3)  the 
distance  of  buildings  from  the  street  lines  and, 
therefore,  the  boundaries  of  adjoining  sites ; 
(4)  the  height  and  depth  of  buildings;  (5) 
the  permissibleness  of  trade  buildings  in 
certain  districts ;  (6)  the  provision  of  a  suit- 


able supply  of  water  and  proper  drainage  ; 
(7)  the  prevention  of  disfigurement  of  streets 
or  squares ;  (8)  the  adaptation  of  street  and 
building  lines  to  the  configuration  of  the  land; 
(9)  the  securing  of  an  adequate  supply  of 
sunshine  in  the  dwellings ;  (10)  the  width  and 
nature  of  streets  and  foot-paths  according  to 
the  requirements  of  local  traffic. 

The  graduation  of  the  width  of  streets  is  as 
follows : — Private  back  roads,  20  ft. ;  macada- 
mised area  of  streets  used  only  for  dwellings, 
25  ft. ;  all  streets  with  continuous  buildings, 
40  ft. ;  those  with  much  business  or  through 
traffic,  56  ft.  wide,  at  least.  The  gradients 
in  streets  must  be  distributed  as  evenly  as 
possible,  and  long  straight  lines  avoided : — 
In  determining  the  directions  of  streets,  care 
must  be  taken  to  provide  short  and  convenient 
connection  between  streets  and  the  chief 
centres  of  traffic.  Open  spaces  and  public 
shrubberies  must  be  arranged  in  convenient 
and  accessible  positions.  Sites  for  churches, 
school  buildings,  and  public  playgrounds 
must  be  provided  in  sufficient  number. 
Continuous  lines  of  buildings  must  be  inter- 
rupted in  sufficient  measure  by  streets.  In 
the  outer  districts,  a  suitable  restriction  of 
the  density  of  building  and  population  must 
be  made.  Front  gardens  must,  as  a  rule, 
have  a  depth  of  at  least  15  ft.,  and  courts  and 
back  gardens  must  be  permanently  secured  as 
such  by  regulations  respecting  their  area  and 
position,  or  by  back  building  lines.  Every 
person  who  builds  must  supply,  at  his  own 
cost,  the  land  for  the  streets  indicated  in  the 
building  plan  along  his  building  plot  to  a 
width  of  84  ft.  in  the  case  of  streets  which 
will  have  buildings  on  both  sides,  and  he  must 
open  up  the  land,  and  make  it  over  to  the 
town ;  unless  the  town  itself  undertakes  this, 
he  must  make  it  into  part  of  the  street,  and 
sewer  it.  In  the  interests  of  traffic  or  of 
health,  existing  buildings  in  a  whole  district 
may  be  compulsorily  acquired  by  the  town 
council,  with  the  sanction  of  the  Ministry  of 
the  Interior,  while  power  is  given  to  purchase 
immediately,  by  compulsion  if  necessary,  any 
land  shown  on  the  building  plan  as  a  proposed 


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TOW 


open  space.  Local  by-laws  may  be  made, 
providing  whether  houses  must  be  detached 
or  semi-detached,  or  built  in  continuous  rows. 
Ugly  or  disfiguring  buildings  can  be  pro- 
hibited, and  by-laws  may  prescribe  higher 
demands  in  respect  of  architectural  character 
and  appearance  of  buildings  to  be  erected  in 
certain  streets  or  parts  of  streets. 

TOWN  PLANNING  IN  SWEDEN — The  Swedish 
Town  Planning  Law  of  1874,  Section  12,  lays 
down  some  of  the  main  points  to  be  aimed  at 
in  town  planning,  as  follows  : — 

(a)  That  streets  shall  be  wide  and  shall  run 
in  the  directions  most  suitable  for  traffic. 

(b)  That  large  and  suitable  sites  shall  be 
provided   for   markets,    harbours,  and   other 
places  where  there  will  be  much  traffic. 

(c)  That  wide   promenades  or   boulevards, 
with  shrubberies  in  the  middle,  and  roadways 
on  either  side,  or  with  other  suitable  arrange- 
ments, shall  traverse  the  town  if  possible  in 
various  places  and  in  different  directions. 

(d)  That  as  many  as  possible  other  public 
planted  open  spaces  shall  be  provided  in  the 
town. 

(e)  That   on  the  one  hand  the   residential 
districts  shall  not  be  so  large  nor  so  crowded 
with  houses  as  to  prevent  the  free  passage  of 
fresh  air,  or  to  interfere  with   the    work   of 
extinguishing  fires,  and,  on  the  other  hand, 
that  in  the  said  districts,  the  building  sites 
shall   be   of    sufficient   size   to  allow   of    the 
erection  of   commodious   dwellings,  and   the 
provision  of  open  and  well- ventilated  yards. 

Section  13  prescribes  widths  of  roads  as 
follows :  — 

Normal  width,  58^  ft.  Specially  exempted 
short  streets,  roads  at  sides  of  boulevards,  and 
streets  with  buildings  only  on  one  side,  may 
have  a  width  of  only  89  ft.  "  Streets  which 
have  front  gardens  on  one  side  or  on  both  sides 
of  them,  provided  that  the  distance  between 
the  two  rows  of  houses  is  at  least  59^  ft., 
may  also  have  a  width  of  not  less  than  39  ft." 

HOLLAND. — Under  the  Housing  Act  of  1901, 
Local  Authorities  in  Holland  have  large 
powers  of  land  purchase  in  connection  with 
town  planning  schemes.  Amsterdam  has 


purchased  4  square  miles  of  land,  and  its 
suburbs,  of  which  2  square  miles  were  taken 
compulsorily,  and  half  the  total  (2  square 
miles),  has  been  planned  as  follows  : — 

Streets,  canals,  and  squares,  420  acres,  or 
35  %  of  the  area. 

Sites  for  exhibitions,  recreation  ground  and 
parks,  300  acres,  or  25  %. 

Sites  for  dwellings  in  streets  or  terraces, 
280  acres. 

Sites  for  villas  and  separately-built  dwell- 
ings, 200  acres. 

No  street  can  be  built  without  the  consent 
of  the  Municipal  Council,  which  has  to 
approve  the  width,  level,  direction,  and 
method  of  construction. 

Local  authorities  are  also  empowered  to 
prohibit  building  or  re-building  on  sites  that 
have  been  reserved  for  streets,  canals,  or 
squares,  in  any  part  of  the  existing  towns. 

HOUSES  PER  ACRE. — In  considering  that  part 
of  town  planning  which  is  concerned  with  the 
proportion  of  building  sites  that  may  be 
covered  by  buildings,  the  following  table  may 
be  of  interest : — 


Country. 


Austria 
Belgium 
Germany     . 
Holland 


Italy    . 


Proportion  of  Building  Site  that  may  be 
covered  by  Buildings. 


85  %  in  majority  of  cases. 

80  %. 

33  to  66  %. 

75  %  in  most  cases,  varying,  how- 
ever, from  20  %  in  rural  districts 
to  80  %  in  urban  areas. 

The  working-class  houses  must 
occupy  not  more  than  80  %. 
(In  Turin  the  proportion  is 
66  %.) 


In  Belgium  the  height  of  buildings  is 
determined  by  the  width  of  streets,  so 
that,  generally  speaking,  the  building  may 
have  a  height  equal  to  the  width  of  the  street, 
plus  20  ft. ;  in  France,  the  free  space  opposite 
a  window  must  be  over  15  ft.,  and  in  some 
parts  of  Paris  30  ft. 

TOWN  PLANNING  IN  ENGLAND. — In  the 
application  of  town  planning  to  England  the 
following  requirements  are  desirable  :  (1)  pro- 
vision for  an  agricultural  belt,  which  should 


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be  kept  permanently  free  from  any  large 
number  of  buildings  ;  (2)  the  planning  of  the 
district  as  a  whole,  providing  for  "  reserves  " 
of  open  space  and  for  large  main  roads  for 
motor  traffic  and  trams,  with  side  roads  for 
shops,  factories,  dwelling-houses,  and  public 
buildings,  while  roads  little  used  for  thorough- 
fares should  be  of  quite  a  different  type ; 
(3)  the  development  of  separate  sites  by 
means  of  a  special  application  or  modification 
of  the  by-laws  limiting  the  number  of  rooms 
per  acre  according  to  circumstances.  Before 
preparing  a  town  plan  there  should  be  a  pre- 
liminary survey  and  inquiry  to  collect  detailed 
information,  historical,  recent  and  present,  as 
to  all  the  factors  affecting  the  growth  of  the 
town.  Maps  and  plans  should  be  prepared  ; 
drawings,  photographs,  pictures,  statistics,  and 
other  detailed  information  should  be  secured 
dealing  with  means  of  communication,  present 
and  anticipated  growth,  movement,  occupa- 
tions, and  distribution  of  population,  with 
anticipated  requirements ;  lines  of  growth 
and  expansion,  and  local  changes  affecting 
streets,  open  spaces,  and  amenities.  There 
should  also  be  collected  town  plans  from  other 
cities,  and  the  whole  of  the  material  so 
obtained  should  be  exhibited  in  order  that 
suggestions  could  be  offered  by  the  public  in 
the  Press,  and  by  experts,  in  addition  to  the 
proposals  drawn  up  by  the  municipal  autho- 
rities. Suggestions  and  designs  should  be 
invited  from  all  quarters,  and  utilised  or 
rejected  after  due  consideration.  Professor 
Geddes  offers  a  valuable  warning  when  he 
urges  that  the  essential  problem  is  to  dis- 
cern "  the  different  character  and  spirit  of 
each  town,  small  or  great,  Chelsea  or  West- 
minster, Dunfermline  or  Edinburgh,  Galway 
or  Dublin,  and  to  collaborate,  plan,  and  work 
towards  a  design  which  shall  increasingly 
express  and  develop  all  that  is  best  in  these, 
and  here  (as  in  individual  life)  we  may  best 
correct  faults  by  developing  qualities.  Town 
plans  which  omit  this  individual  point  of 
view,  which  has  nowhere  been  sufficiently 
considered,  are  not  even  adequate  as  '  town 
patches.'  Thus,  the  great  American  sea- 


port would  not  copy  the  modern  defects  of 
Berlin  if  it  knew  the  best,  say,  of  Hamburg 
and  Lubeck,  old  and  new."  He  also  does 
right  in  urging  us  to  "  avoid  a  too  crude  and 
hasty  adoption  of  city  plans,  inspired  not  by 
local  life,  by  love,  or  knowledge,  but  by  imita- 
tion of  the  costly  and  meretricious  pomposities 
of  great  Continental  capitals.  Haussmann's 
Paris,  the  Ecole  des  Beaux  Arts,  Modern  Ber- 
lin and  Vienna,  have,  in  this  respect,  a  widen- 
ing influence  upon  their  annually  increasing 
multitude  of  visitors  from  America  and 
Britain ;  and  already  the  visitors  to  almost 
any  important  city  of  these  islands,  must  see 
this  influence.  For  this  increasingly  threatens 
us  with  dreary  perspectives  and  conventional 
ornament,  relieved  only  by  occasional  extra- 
vagances, and  is  thus,  as  with  the  least  artistic 
sense  and  training  any  one  can  see  for  him- 
self, even  uglier  than  the,  as  yet,  prevalent 
industrial  squalor  and  garishness  of  our 
poorer  quarters,  or  even  than  the  featureless 
monotony  of  our  respectable  ones.  In  a  word, 
an  immediate  danger  in  America  (and  in 
Britain  also)  is  to  repeat  the  mistakes  of  the 
French  '  city  improvers  '  of  the  Second  Em- 
pire, and  the  corresponding  developments  of 
Berlin,  Strasburg,  &c."  W.  T. 

Trade  Effluents. — The  rapid  development 
of  industries  producing  effluents  containing 
waste  products  either  in  suspension  or  solu- 
tion has  greatly  increased  the  pollution  of 
rivers  in  manufacturing  centres.  The  puri- 
fication of  these  effluents  either  alone  or  when 
mixed  with  ordinary  sewage  forms  a  special 
problem  and  has  been  the  subject  of  consider- 
able special  legislation.  The  polluting  effect 
of  trade  effluents  may  be  due  to  the  presence 
of  :  (a)  an  excessive  quantity  of  suspended 
solids;  (l>)  substances  capable  of  fermentation 
or  putrefaction  and  consequent  production  of 
nuisance;  (c)  colouring  matters  such  as  vege- 
table or  artificial  dye-stuffs ;  (d)  substances 
poisonous  to  aquatic  vegetation  or  fish  life ; 
(e)  oily  matters,  fat  and  soap. 

The  detailed  description  of  these  various 
classes  of  effluents  and  their  respective 


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methods  of  treatment  is  briefly  indicated  in 
the  following  paragraphs,  it  being  understood 
that  one  effluent  may  fall  under  more  than 
one  head. 

(a)  Tannery  effluents  contain  large  quan- 
tities of  lime  in  suspension  ;  effluents  from 
plants  for  the  recovery  of  ammonia  from 
liquors  produced  in  the  distillation  of  coal  in 
gas-retorts  or  coke  ovens  contain  large  quan- 
tities of  lime  and  calcium  sulphide  and  sul- 
phate in  suspension ;  effluents  from  coal- 
washing  plants  contain  much  fine  coal  in 
suspension;  pottery  effluents  contain  clay; 
effluents  from  aniline  stills  may  contain  large 
quantities  of  magnetic  oxide  of  iron ;  effluents 
from  dye  and  bleach  works  may  contain  much 
flocculent  matter  from  waste  "filling"  or 
mordanting  substances  and  fibrous  material 
from  the  cloth  itself ;  paper-mill  effluents  may 
also  contain  fibre  and  "  filling."  Most  of 
these  can  be  clarified  by  simple  subsidence  in 
suitably  constructed  settling  tanks.  In  certain 
cases,  e.g.,  for  paper-mill  effluents,  mechanical 
filters  or  fine  screens  may  be  employed. 
(b)  Among  important  fermentative  or  putre- 
factive effluents  are  those  from  breweries  and 
distilleries,  from  tanneries  and  hide-dressing 
works,  from  beetroot  sugar  factories,  starch 
works,  wool-scouring  works,  bone  manure  and 
glue  factories.  All  of  these  can  be  purified 
by  suitably-arranged  biological  tanks  and 
filters,  either  at  the  actual  works  producing 
the  effluent,  or  mixed  with  sewage  at  the 
works  of  the  local  authority.  It  should  be 
noted  that  liquids  capable  of  undergoing  acid 
fermentation,  e.g.,  starchy  effluents  or  brewery 
effluents  are  not  well  suited  for  anaerobic  treat- 
ment, (c)  Colouring  matters  from  dye-works 
may  be  of  vegetable  origin,  such  as  indigo  or 
logwood,  or  belong  to  the  numberless  varieties 
of  so-called  "  aniline  "  or  artificial  dye-stuffs. 
The  former  and  certain  of  the  latter,  e.g., 
alizarine  derivatives,  which  are  fixed  by  mor- 
dants, can  be  precipitated  by  means  of  iron 
or  aluminium  salts.  A  large  proportion  of 
artificial  colouring  matters  are  not  capable  of 
removal  in  this  way.  They  are  generally 
destroyed  in  biological  filters  when  mixed  with 


sewage,  but  apart  from  their  colour  do  not 
constitute  a  dangerous  element  in  effluents. 
(d)  A  great  variety  of  injurious  substances 
maybe  discharged  under  this  head,  e.g.,  alkaline 
sulphides  from  alkali  waste  heaps,  from  the 
vulcanising  of  india-rubber,  from  dyeing  pro- 
cesses employing  sulphur  dye  stuffs,  and  in 
certain  cases  the  effluents  from  ammonia 
recovery  stills.  It  is  highly  important  that 
these  should  be  treated  either  with  excess  of 
lime  or  a  mixture  of  lime  and  ferrous  sulphate 
(copperas),  and  the  precipitated  sulphide 
settled  out  in  tanks,  before  the  effluent  is 
discharged  either  into  a  sewer  or  a  water- 
course, or  there  is  almost  a  certainty  of  seri- 
ous nuisance  or  even  fatal  accidents  arising 
from  the  evolution  of  sulphuretted  hydrogen, 
due  to  chance  contact  of  such  an  effluent  with 
free  acid. 

Acids  and  alkalis  unless  present  in  very 
minute  proportion  should  be  neutralised 
before  discharge  into  a  stream  or  sewer. 

Chlorine  either  in  the  free. state  or  as  hypo- 
chlorite  in  bleach  works  effluents,  unless 
present  in  very  large  quantities,  is  not  likely 
to  be  very  troublesome  when  discharged  into 
a  sewer,  but  it  is  important,  from  the  point  of 
view  of  fish  life  and  aquatic  vegetation,  that 
only  nominal  quantities  should  be  allowed  to 
pass  direct  into  a  stream.  Numerous  tarry 
products  such  as  benzol  and  naphthalene 
washings  containing  sulphuric  acids  of  ben- 
zene and  naphthalene,  various  phenolic  deriva- 
tives, &c.,  are  very  injurious  to  the  microscopic 
life  of  streams,  and  may  in  some  cases  quite 
upset  the  natural  balance  of  aquatic  life. 
When  sufficiently  diluted  and  mixed  with 
sewage,  they  are  amenable  in  general  to  bio- 
logical treatment.  The  same  applies  to  the 
very  troublesome  effluents  from  ammonia 
stills  treating  the  liquor  from  the  distillation 
of  coal  in  retorts  or  coke  ovens.  In  addition 
to  phenolic  derivatives  these  effluents  contain 
sulphocyanates,  thiosulphates,  and  sometimes 
sulphides.  The  effluents  from  paper  and 
cellulose  works  obtained  after  boiling  raw 
cellulose  material  with  alkaline  sulphites 
is  very  difficult  to  treat  and  is  generally 


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evaporated,  (e)  Free  particles  of  grease  and 
fat,  e.g.,  from  tripe-dressing  works,  &c.,  can 
usually  be  intercepted  by  specially  devised 
grease  traps,  of  which  there  are  several,  e.g., 
the  Kremer  apparatus  and  the  Eric  Mesten 
apparatus. 

Soaps,  e.g.,  such  as  are  produced  in  wool- 
scouring  works,  are  first  broken  up  by  acid, 
when  the  fatty  acids  rise  to  the  surface  and 
can  be  separated  and  purified.  In  the  case 
of  ordinary  laundries  it  is  often  simpler  to 
precipitate  the  soaps  with  lime. 

LAW  AS  TO  TKADE  EFFLUENTS. — The  general 
law  as  to  trade  effluents  is  to  be  found  in  the 
Public  Health  Act,  1875,  the  Rivers  Pollution 
Act,  1876,  The  Public  Health  Acts  Amend- 
ment Act,  1890.  The  difficulties  of  inter- 
pretation of  the  law  have  centred  round  the 
liability  of  local  authorities  to  take  trade 
effluents  into  sewers,  when  either  these  were 
insufficient  in  size  or  when,  the  sewers  being 
adequate,  the  purifying  works  were  over- 
burdened. A  further  difficulty  has  arisen  in 
regard  to  responsibility  for  pollution  of  a 
stream,  when  a  manufacturer  discharges  into 
a  sewer  belonging  to  a  local  authority. 
Typical  cases  illustrating  each  of  these  three 
difficulties  are,  respectively :  Peebles  v.  Oswald - 
twistle  Local  Board,  1898 ;  Brook,  Ltd.  v. 
Meltham  Urban  District  Council,  September, 
1908;  Rutlencorth  <£  Roberts  v.  West  Riding 
Rivers  Board,  November  26,  1908.  All  of 
these  have  been  decided  on  appeal  in  a  sense 
favourable  to  the  local  authority.  It  is 
generally  the  wish  of  the  local  authority  to 
encourage  manufacturers  as  far  as  possible, 
and  several  towns  have  special  by-laws  of 
their  own  obtained  generally  by  mutual  agree- 
ment with  manufacturers,  confirmed  in  some 
cases  by  special  Acts  of  Parliament.  Thus, 
the  towns  of  Bradford  and  Halifax  have  power 
to  impose  a  charge  upon  manufacturers, 
according  to  the  volume  and  quality  of  the 
effluents  sent  into  the  sewers ;  Manchester 
has  special  powers  regulating  the  composition 
of  the  effluents  discharged  into  the  sewers, 
but  does  not  make  any  charge  for  treatment. 
These  powers  are  based  on  similar  ones  pos- 


sessed by  the  London  County  Council.  The 
Eoyal  Commission  on  Sewage  Disposal  recom- 
mended in  their  third  report,  1903,  that  in 
general  local  authorities  should  receive  trade 
effluents  into  sewers,  but  that  either  prelimi- 
nary treatment  should  be  adopted  by  the 
manufacturer  or  he  should  pay  a  special 
charge  to  go  to  the  cost  of  treatment  of  his 
effluent.  Points  of  difference  likely  to  arise 
between  manufacturers  and  local  authorities, 
they  recommend,  should  be  referred  to  the 
central  authority  which  they  are  of  opinion 
should  be  appointed.  G.  J.  F. 

Tramways,  Municipal. — Overhead  Trolley 
System  —  Conduit  System  —  Surface  Contact 
System — Comparison  of  Tramway  Systems. — 
A  tramway  system  comprising  not  more  than 
twenty  or  thirty  cars  should  purchase  its 
electricity  from  some  large  electricity  supply 
station,  wherever  such  is  available.  The 
multiplication  of  small  stations  is  a  mistaken 
policy,  and  is  largely  responsible  for  the 
unsatisfactory  commercial  results  which  have 
been  obtained  in  the  case  of  a  large  percentage 
of  the  tramways  in  this  country. 

For  tramway  undertakings  of  any  consider- 
able extent,  the  electricity  should  first  be 
delivered  from,  the  supply  station  in  the  high 
pressure  three-phase  form.  In  this  form  it 
should  be  transmitted  through  three-core 
paper-insulated  lead-covered  cables  to  sub- 
stations located  at  appropriate  points  on  the 
tramway  route.  The  sub- stations  should  lie 
equipped  with  motor-generators,  by  means  of 
which  the  high  pressure  three-phase  elec- 
tricity is  transformed  into  continuous  electricity 
at  the  low  pressure  of  550  or  600  volts. 

This  low-pressure  electricity  is  transmitted 
from  the  sub-stations  to  the  tramcars  by  one 
or  other  of  the  following  three  systems  : 

1.  The  Overhead  Trolley  System. 

2.  The  Conduit  System. 

8.  The  Surface  Contact  System. 

1.  OVERHEAD  TROLLEY  SYSTEM. — A  copper 
conductor,  usually  between  2/0  and  4/0  S.W.G. 
is  supported  on  insulators  at  a  height  of 


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MUNICIPAL   AND    SANITAEY   ENGINEERING. 


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some  20  ft.  above  the  track,  by  means  of 
transverse  steel  span  wires  carried  by  poles. 
This  overhead  copper  trolley  wire  conducts 
the  electricity  from  the  sub-station  to  the 
tramcar.  The  tramcar  is  supplied  with  a 
trolley  pole  carrying  a  wheel  or  bow  at  its 
upper  end.  The  wheel  or  bow  travels  on  the 
lower  surface  of  the  overhead  wire,  collecting 
the  electricity,  which  is  then  conducted  to  the 
motors  and  controlling  apparatus  on  the  car. 
After  passing  through  this  apparatus,  the 
electricity  is  conducted  to  the  car  wheels,  and 
thence  to  the  rails.  The  rails  are  connected 
to  one  another  by  copper  bonds,  and  thus  con- 
stitute a  conductor  by  means  of  which  the 
electricity  is  conveyed  back  to  the  sub-station. 
Sometimes  the  rails  are  welded  together 
instead  of  being  bonded. 

2.  CONDUIT  SYSTEM. — The  most  modern 
example  of  tramway  construction  on  the 
conduit  system  is  that  laid  down  by  the 
London  County  Council  in  many  parts  of 
London  and  its  suburbs.  The  conductors  are 
located  in  a  conduit  situated  midway  between 
the  track  rails,  and  the  current  is  collected 
from  these  conductors  by  means  of  a  "  plough  " 
passing  through  a  slot  in  the  road  bed,  and 
suspended  from  the  car.  In  one  of  the  earlier 
forms  of  conduit  construction,  the  conduit 
was  made  a  component  part  of  one  of  the 
track  rails.  The  track  rails  were  formed  by 
two  bull-headed  rails,  placed  side  by  side,  with 
sufficient  space  between  to  allow  the  collector 
or  "  plough  "  to  pass  through.  The  advantage 
of  this  side-slot  construction  is  that  it  does 
not  require  keeping  gauged,  but  a  strong  dis- 
advantage is  the  impracticability  of  obtaining 
a  substantial  permanent-way  for  the  heavy 
cars.  The  London  County  Council  system 
has  the  slot  midway  between  the  track  rails, 
the  slot  being  formed  by  Z  section  rails, 
bolted  at  intervals  to  heavy  cast-iron  yokes, 
the  width  of  the  slot  being  maintained  as 
near  f  in.  as  possible.  The  slot  rail  is  of 
steel  weighing  60  Ibs.  per  yard,  and  is  7  in. 
in  height. 

Two  forms  of  yokes  are  used  in  the  system, 
one,  of  light  weight,  to  which  the  slot  rails  only 


are  bolted,  and  another,  the  full  width  of  the 
track,  to  which  both  the  slot  rails  and  the  track 
rails  are  bolted.  These  two  types  of  yoke  are,  in 
special  places,  such  as  at  curves,  &c.,  placed 
alternately,  but  in  straight  track  the  full-width 
yokes  are  placed  about  every  three  yokes,  the 
distance  between  each  yoke  being  5  ft.  The 
slot  rails  have  to  be  stiffened  by  means  of 
ties  fastened  to  the  track  rails  in  order  to 
prevent  the  slot  from  closing  under  the 
influence  of  the  crushing  effect  of  other  traffic 
upon  the  paving  between  the  slot  and  track 
rails.  The  conductors  are  two  in  number 
and  are  of  soft  steel  tees  weighing  22  Ibs.  to 
the  yard.  They  have  a  contact  surface  3|  in. 
in  depth,  and  are  supported  on  special 
insulators,  spaced  15  ft.  apart,  and  situated 
between  the  yokes. 

The  depth  from  the  top  of  the  slot  rail  to 
the  bottom  of  the  conduit  tube  is  1  ft.  9^  in., 
and  to  the  base  of  the  yokes,  where  the  latter 
bear  in  the  concrete  bed,  1  ft.  llin.  Thus, 
during  the  construction  of  a. conduit  system, 
all  gas,  water  and  other  pipes,  cables,  sewers, 
&c.,  must  be  sunk  at  least  23  in.  below  the 
surface  of  the  road,  before  the  conduit  can  be 
laid  down. 

The  "  plough  "  or  collecting  device  consists 
of  two  soft  cast-iron  shoes,  supported  by 
pieces  of  maple  wood,  which  are  stiffened  and 
supported  by  means  of  mild  steel  plates, 
passing  through  the  slot,  these  steel  plates 
being  flexibly  hung  from  the  under-frame  of 
the  car.  The  shoes  are  pressed  against  the 
face  of  the  tee  conductors  by  means  of  sub- 
stantial springs. 

To  allow  proper  draining  and  sanitation  of 
the  conduits,  they  are,  at  intervals  along  the 
route,  connected  to  the  main  sewers,  which 
generally  run  along  the  side  of  the  conduit. 

8.  SUEFACE  CONTACT  SYSTEM. — There  have 
been  many  surface  contact  systems  invented, 
but  few  have  actually  been  put  into  practice. 
These  latter  have,  moreover,  usually  proved 
utterly  unreliable.  The  surface  contact 
system  consists  essentially  of  contact  studs, 
located  at  intervals  of  about  15  ft.  apart, 
situated  midway  between  the  track  rails,  and 


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from  which  the  current  is  collected  by  means 
of  "  skates."  The  two  essential  conditions 
which  must  be  fulfilled  in  a  system  of  this 
kind  are : — 

(1)  The   contact   stud   must   not  be  alive 
when  the  car  is  not  over  it,  i.e.,  when  the  car 
is  not  drawing  energy  from  it,  and 

(2)  Some  arrangement  has  to  be  provided 
to  make  the  contact  stud  alive  when  the  car 
approaches  it.     Apparently  one  of  the  least 
unsuccessful  of  all  the  systems  on  these  prin- 
ciples is  that  commonly  known  as  the  "  G.  B. 
System."     In  this  system  the  current  from 
the  generating  station  is  conveyed  through  a 
bare  stranded  galvanised   iron  cable,  carried 
on    insulators    in     a    5  in.    stoneware  pipe 
which     serves    as  a    conduit.       Connection 
between  the  conductor  and  the  contact  stud  is 
effected  magnetically  by  means  of    powerful 
magnets    carried   on    the   car.     When   these 
car  magnets  come  over  the  contact  stud,  a 
plunger    switch,    having   a    carbon    contact, 
immediately  makes    contact    with   the    iron 
cable  conductor.     When  the  car    leaves  the 
stud,  the  plunger  switch  is  immediately  dis- 
connected by   means  of   a   powerful   spring. 
The   excavation   necessary  with  this  system 
does  not  exceed  19  in.,  and  this  can  be  con- 
siderably reduced  in  special  places  where  so 
great  a  depth  is  inexpedient. 

COMPARISON  OF  TRAMWAY  SYSTEMS.  —  The 
most  important  applications  of  the  overhead 
trolley  systems  are  in  country  districts  and  in 
towns  of  fairly  small  population.  In  some 
large  towns,  overhead  trolley  systems  are 
often  prohibited.  In  residential  districts, 
objections  based  on  aesthetic  grounds  are  often 
brought  up  against  the  system.  Nevertheless 
very  nearly  all  of  the  tramway  undertakings 
in  the  United  Kingdom  are  constructed  on 
this  system.  The  capital  cost  of  the  conduit 
system  precludes  its  use  in  purely  residential 
districts.  Conduit  systems  are  only  appro- 
priate in  large  towns  where  a  dense  service 
can  be  maintained,  and  where,  for  other 
reasons,  the  trolley  system  is  undesirable. 

Under  normal  conditions  the  cost  of  track- 
work  per  mile  (excluding  cables  and  other 


items  common  to  all  three  systems),  is 
somewhat  as  follows,  for  the  three  different 
systems : — 

Conduit  System         £17,000. 

"  G.B.  Surface  Contact  System  "  £11,000. 

Overhead  Trolley  System     ...     £10,000. 

From  these  figures  we  see  that  the  conduit 
system  involves  a  capital  outlay  approximately 
£7,000  greater  per  mile,  than  in  the  case  of 
the  overhead  trolley  system.  In  order  to 
understand  the  significance  of  this  difference 
let  a  simple  example  be  taken.  Suppose  a 
tramway  system  is  one  mile  in  length,  and  a 
service  of  two-and-a-half  minutes  for  16  hours 
per  day  is  maintained.  Then,  if  we  consider 
a  double  track  the  whole  length  of  the  system, 
the  car  miles  per  year  will  amount  to 

16  X  60  X  365 


2-5 


—  280000. 


Allowing  10  %  for  interest  and  depre- 
ciation, then  this  £7,000  difference  in  capital 
cost  between  the  two  systems  is  equivalent 
to  £700  expenditure  per  annum. 

Thus  the  difference  in  interest  and  depre- 
ciation per  car  mile  amounts  to  some 
700  X  240 


280000 

The  conduit  has  to  be  kept  clean,  both  for 
insulation  and  sanitary  purposes,  and  this 
maintenance  cost  is  certainly  at  least  0'3<i.  per 
car  mile  in  excess  of  the  trolley  system.  Thus 
the  total  difference  between  the  two  systems 
amounts  to  0'60  -f  0'30  =  O'QOd  per  car 
mile.  Assuming  an  average  operating  cost  of 
6'5d.  for  the  overhead  trolley  system,  this 
maintenance  and  capital  cost  will  represent 
an  extra  13  %,  or  a  total  operating  cost  of 
7'4d.  per  car  mile  for  the  conduit  system. 

In  the  conduit  system  there  are  no  electro- 
lytic actions  occurring  in  water  pipes  and 
elsewhere,  due  to  currents  leaking  from  the 
return  conductor,  because  an  insulated  con- 
ductor in  the  conduit  itself  serves  to  carry 
the  return  current,  whilst  in  the  trolley  system 
the  current  is  returned  through  the  track  rails. 
It  is  with  a  view  to  minimising  electrolytic 
damage  to  underground  pipes  and  structures 


476 


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MUNICIPAL   AND   SANITAEY   ENGINEERING. 


TRA 


that  the  Board  of  Trade  require  that,  with 
the  overhead  trolley  system,  the  drop  of 
pressure  in  the  rail  return  shall  never  exceed 
7  volts. 

From  the  point  of  view  of  the  safety  of  the 
public,  the  conduit  system  undoubtedly 
possesses  some  advantage.  There  are  no 
"  live "  wires  above  the  ground,  and  it  is 
impossible  to  touch  the  conductor  in  the 
conduit  by  any  ordinary  means,  through  the 
slot  opening.  With  overhead  construction, 
the  Board  of  Trade  require  protection  for 
telephone  wires  and  cables  which  may  happen 
to  cross  the  trolley  wire.  That  is  to  say,  if  a 
telephone  wire  breaks,  it  must  not  be  possible 
for  it  to  fall  across  the  "  live "  wires.  To 
prevent  this,  grounded  "  guard  "  wires  are 
suspended  above  the  trolley  wires. 

As  regards  durability,  the  steel  conductors 
of  the  conduit  system  have  a  longer  life  than 
the  ordinary  copper  trolley  wire.  The  latter 
in  ordinary  services  will  last  some  4  years. 

A  disadvantage  of  the  conduit  system  lies 
in  the  fact  that  the  slot  is  very  liable  to  close, 
due  to  the  pressure  of  the  wood  or  stone 
paving.  Thus  the  plough  is  liable  to  become 
wedged  in  the  slot  and  cause  delay  in  the 
traffic. 

The  serious  difficulty  with  the  surface  con- 
tact system  is  its  unreliability.  Experience 
has  proved  that  the  studs  are  sometimes  left 
alive,  in  spite  of  every  precaution  to  render 
such  occurrences  impossible.  In  view  of  this 
difficulty,  extra  skates  are  sometimes  pro- 
vided on  each  car.  These  trail  behind  the 
collecting  skate,  and  in  case  of  a  stud  being 
left  alive  the  trailing  skate  directly  short- 
circuits  the  stud  with  the  track  rail,  thus 
putting  the  stud  out  of  action  for  the  time 
being.  The  maintenance  costs  of  the  surface 
contact  system  are  certainly  not  less  and  are 
usually  far  higher  than  for  either  the  trolley 
or  conduit  systems,  and  this  will  occasion  no 
surprise  when  it  is  remembered  that  hundreds 
of  switches  per  mile  have  to  be  kept  in 
thorough  working  order. 

ACTS  OF  PARLIAMENT  AFFECTING  THE  OPERA- 
TION OF  MUNICIPAL  TRAMWAYS. — Provisional 


Orders  authorising  the  construction  of  tram- 
ways were  granted  under  the  powers  of  the 
Tramways  Act  of  1870.  It  was  stated,  how- 
ever, when  the  Bill  was  introduced,  that  power 
would  be  given  local  authorities  only  to  con- 
struct tramways,  but  not  to  work  them. 

The  "  Purchase  Clause  "  of  the  Act  of  1870 
imposed  upon  the  private  tramway  companies 
the  liability  of  compulsory  sale  to  the  local 
authority  of  the  district.  Under  this  clause 
the  local  authority  may,  within  6  months 
after  the  expiration  of  21  years  from 
the  granting  of  the  tramway  order,  and 
within  6  months  after  every  subsequent 
period  of  7  years,  require  the  promoters 
to  sell  their  undertaking.  It  is  now  possible 
under  the  present  rules,  for  municipalities  to 
operate  tramways,  as  well  as  to  construct 
them.  No  Act  of  Parliament,  however, 
authorises  them  to  do  so  without  special 
grants,  and  it  was  due,  among  other  reasons 
to  the  difficulty  of  coming  to  an  understand- 
ing as  regards  lease,  &c.,  with  the  companies, 
that  led  certain  municipalities  to  obtain  these 
special  grants. 

A  municipality  is  allowed  to  construct 
tramways  outside  its  own  area,  providing  the 
consent  of  the  local  authority  of  the  new  area 
is  obtained.  The  local  authority  of  the  new 
area  still,  however,  retains  its  power  of  com- 
pulsory purchase  under  the  conditions  given 
in  the  Purchase  Clause  of  the  1870  Act, 
given  above. 

The  local  authorities  must  obtain  the  con- 
sent of  the  Board  of  Trade  with  respect  to 
the  power  of  borrowing  capital. 

With  regard  to  constructional  obligations, 
the  1870  Act  contains  clauses  to  the  effect 
that  no  tramway  may  be  so  laid  that  for  a 
distance  of  30  ft.,  less  space  than  9  ft.  6  in. 
intervenes  between  the  foot-path  and  the  rail, 
if  one-third  of  the  occupiers  abutting  on  that 
part  of  the  road  dissent. 

The  tramway  constructors  are  bound  to 
keep  the  roadway  in  repair  to  the  extent  of 
18  in.  on  each  side  of  their  rails,  and  between 
double  lines. 

The  Light  Railways  Act  of  1896,  although 


477 


TRA 


ENCYCLOPAEDIA   OF 


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not  applying  strictly  to  tram- 
ways, has,  however,  been  applied 
to  a  large  extent  for  tramway 
purposes.  The  procedure  under 
this  Act  is  governed  In-  rules 
issued  by  the  Board  of  Trade. 

A  very  lucid  survey  of  the 
financial  aspects  of  the  muni- 
cipal tramway  situation  has 
been  published  by  Mr.  E. 
Garcke,  in  a  little  book  entitled 
"  The  Progress  of  Electrical 
Enterprise,"  Electrical  Press, 
Ltd.,  London,  1907.  Details 
of  tramway  construction  are 
ably  set  forth  in  Vol.  1,  of 
Wilson  &  Lydall's  "  Electrical 
Traction."  Excellent  descrip- 
tions of  various  systems,  accom- 
panied by  analyses  of  their 
finances  will  be  found  in  Prof. 
E.  H.  Smith's  "  Electric  Trac- 
tion," Harper  &  Bros.,  1905. 
Another  capital  treatise  on 
tramways  is  Ashe  &  Kelly's 
"  Electric  Railways,"  published 
in  two  volumes,  by  Messrs. 
Constable  &  Co.,  Ltd.,  London, 
1907. 

As  regards  applications  of 
electric  traction  on  a  larger 
scale  than  for  tramways,  and 
to  overhead,  underground,  urban 
and  suburban  railways,  Par- 
shall  &  Hobart's  ''  Electric 
Piailway  Engineering  "  may  be 
consulted. 

By  permission  of  the  pub- 
lishers of  the  "  Electrical 
Times,"  a  table,  giving  the 
summarised  records  of  electric 
tramway  undertakings  has  been 
added.  In  the  first  two  columns 
the  figures  are  for  private  com- 
panies for  the  financial  years 
of  1905  and  1906.  In  the 
second  two  columns  are  given 
equivalent  figures  for  tramway 


478 


TRA 


MUNICIPAL   AND   SANITARY   ENGINEERING. 


TUR 


undertakings  owned  and  worked  by  local 
authorities  for  the  financial  years  1906-7 
and  1905-6.  In  the  last  two  columns,  these 
separate  figures  for  companies  and  local 
authorities  are  added  under  their  equivalent 
financial  years. 

For  notes  with  regard  to  the  generation, 
transmission  and  transformation  of  the  elec- 
tricity required  for  the  propulsion  of  tramcars, 
see  article  on  "ELECTRICITY." 

Trap. — A  term  applied  to  the  dip  or  bend 
in  a  drain  or  pipe,  which,  by  retaining  water, 
serves  to  break  the  direct  line  of  connection 
between  the  air  contained  by  two  portions 
thereof.  The  water  retained  is  said  to  "seal" 
the  trap  ;  the  effective  seal  being  the  portion 
contained  between  the  standing  level  of  the 


A  - 


Trap. 

water  and  the  lowest  point  of  the  soffit  at  the 
dip  of  the  trap  (^4- — B  in  the  illustration).  It 
is  the  depth  of  this  portion  which  is  referred 
to  by  the  phrase  "  a  water-seal  of  so  many 
inches."  One-and-a-half  inches  is  considered 
the  minimum  seal  admissible,  and  2J  in.  the 
seal  generally  accepted  as  the  standard.  Traps 
may  be  subdivided  into  traps  of  fittings, 
gullies,  disconnecting  traps  and  grease  traps, 
as  to  which  see  under  respective  headings. 

Traps  for  Fittings  are  necessary  to 
exclude  from  the  house  foul  air  generated  in 
waste  pipes  and  surface  traps,  &c.  In  the 
case  of  water-closets  and  of  most  slop  hoppers 
the  trap  is  made  as  a  part  of  the  fitting  itself. 
With  lavatory  basins,  baths,  sinks  and  urinals 
the  trap  must  be  specially  provided,  and 
should  be  fixed  on  the  waste  pipe  close  up  to 
the  fitting.  Such  traps  must  be,  as  far  as 
possible,  self-cleansing,  and  should  provide  an 


efficient  seal  with  a  minimum  quantity  of 
water.  The  only  traps  at  present  available 
which  comply  with  these  requirements  are  the 
siphon  traps  drawn  from  lead  piping  and 
made  in  various  forms,  such  as  the  "  S," 
"  P,"  and  others.  All  other  traps — such  as 
the  "Bell"  trap,  "D"  trap,  "Bottle"  trap, 
and  the  "  Mechanical  "  traps  in  which  latter 
are  floating  balls  or  valves — are  either  ineffi- 
cient or  uncleanly.  The  traps  used  must  be 
of  the  same  or  of  a  smaller  sectional  area  than 
those  of  the  outlets  under  which  they  are 
fixed ;  due  allowance  being  made  for  the  space 
obstructed  by  the  outlet  gratings.  If  larger, 
they  will  not  be  properly  flushed  and  cleaned 
by  the  discharge  of  the  fittings. 

Turbines. — In  an  ordinary  water-wheel 
only  a  portion  of  the  periphery  is  acted  upon 
by  the  water,  but  in  turbines  it  is,  with  few 
exceptions,  directed  by  guide  blades  to  every 
vane  in  the  revolving  part ;  the  wheel  of  a 
turbine  thus  receives  the  pressure,  or  in  some 
cases  the  impulse,  of  the  water  throughout  its 
circumference.  For  this  reason  it  is  much 
smaller  and  revolves  at  a  far  higher  speed 
than  a  water-wheel  of  equal  power.  Both 
guides  and  vanes  are  curved  in  such  a  way 


FIG.  1. — Headrace  and  Supply  of  Water  to  Turbine. 

that  the  water  passes  from  one  to  the  other 
without  shock  or  break  of  continuity  and 
herein  lies  the  cause  of  the  high  efficiency, 
amounting,  under  favourable  circumstances, 
to  over  80%.  Turbines  may  be  of  the 
"pressure"  or  the  "impulse"  type.  The 
former  are  those  in  which  the  spaces  between 
the  vanes  are  full  and  under  the  pressure  of 
the  water.  In  impulse  turbines,  such  as  the 
"  Girard  "  the  water  acts  by  impulse,  leaving 
the  guides  with  a  velocity  proportionate  to 
the  head,  and  entering  the  wheel  to  glide  over 


479 


TUR 


ENCYCLOPAEDIA   OF 


TUR 


the  concave  surface  of  the  vanes  without 
filling  the  passages.  In  some  cases  the 
guides  of  impulse  turbines  are  only  applied  to 
a  portion  of  the  wheel — this  is  known  as 
"partial"  admission.  The  "  Pelton  wheel" 
belongs  to  this  class — in  this  case  one  or  more 


the  guide  blades,  which  are  then  made  mov- 
able for  that  purpose,  or  by  throttling  the 
supply  with  a  cylindrical  sluice  working 
between  the  guide  chamber  and  the  wheel ;  in 
a  few  cases,  however,  an  adjustable  gate  is 
placed  at  the  intake.  The  first  plan  gives  the 


FIG.  2. — General  Arrangement  of  Fixing  of  Turbine. 


tapering  nozzles  direct  a  jet  of  water  into 
double  cups  placed  around  the  rim  of  a  wheel. 
Turbines  may  be  classified  as  "  outward," 
"inward,"  "parallel"  or  "mixed"  flow, 
according  to  the  direction  in  which  the  water 
passes  through  them.  In  the  first  type, 
(Fourneyron's)  the  guides  form  the  central 
part  of  the  turbine,  the  wheel  containing  the 
vanes  being  placed  outside  it  and  in  the  same 
plane.  The  water  enters  the  inner  portion 
and  is  directed  by  the  guide  passages  to  the 
annulus  of  vanes  surrounding  it,  giving 
motion  to  that  part  by  pressure  and  reaction 
and  afterwards  escaping  at  its  periphery.  In 
the  second  type  ("  vortex  ")  the  water  enters 
through  guide  passages  on  the  outside  of  the 
wheel  and  discharges  at  the  centre.  With 
the  parallel  flow  turbine  ("  Jonval  "  type)  the 
guides  are  placed  above,  or  if  the  shaft  is 
horizontal  to  one  side  of  the  vanes,  and  the 
water  passes  through  in  a  direction  parallel 
with  the  axis.  The  mixed  type  is  a  combina- 
tion of  the  inward  and  parallel  flow,  and  is 
represented  by  the  "  Francis,"  "  Hercules," 
"  Little  Giant,"  and  others.  Turbines  are 
usually  regulated  by  varying  the  opening  of 


most  economical  regulation  under  varying 
loads,  but  it  is  more  complex  and  therefore 
higher  in  first  cost.  For  low  falls  where  the 
quantity  of  water  is  large,  pressure  turbines 
of  the  parallel  and  mixed  type  are  the  most 
suitable.  Under  these  circumstances  the 


FIG.  3. — "Double  Vortex"  Turbine. 

water  is  conveyed  to  the  turbine  by  a  "flume" 
of  timber  or  masonry,  the  general  arrange- 
ment being  usually  as  shown  in  Fig.  2 ;  the 
dotted  circle  indicates  how  a  breast  wheel 
might  be  replaced  by  a  turbine.  For  moderate 
falls  of  10  ft.  and  upwards  it  is  generally 
preferable  to  inclose  the  turbine  in  an  iron 


480 


TYP 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


TYP 


case  to  which  the  water  is  conducted  by  piping. 
By  causing  part  of  the  fall  to  act  by  suction, 
a  turbine  may  be  placed  well  above  the  tail 
race  and  the  machinery  driven  by  belting  or 
coupled  directly  to  its  shaft.  Fig.  8  shows  a 
"Double  Vortex"  installed  in  this  way,  but 
the  arrangement  would  apply  generally  to  any 
other,  incased  turbine  with  a  horizontal  shaft. 
Fig.  4  illustrates  the  mode  of  fixing  a  Little 
Giant  turbine ;  in  this  example  the  turbine 
replaced  an  overshot  wheel,  the  pentrough  of 
which  was  utilised  in  the  manner  shown.  A 
Girard  turbine  could  be  similarly  arranged 
except  that  it  would  be  placed  a  few  inches 
above  tail  wrater  to  insure  a  free  discharge. 
Suction  tubes  cannot  be  employed  in  an 
impulse  turbine  owing  to  the  passages  being 
only  partially  filled  ;  therefore, 
to  obtain  the  full  effect  of  the 
fall,  which  in  one  of  low  head 
is  important,  it  must  be  placed 
close  to  the  tail  water,  in  which 
position  it  is  liable  to  have  its 
efficiencyimpaired  duringfloods. 
WTith  high  falls  a  slight  sacrifice  of  head  is  not 
of  so  much  consequence,  and  to  them,  impulse 
turbines  of  the  Girard  type  are  specially  applic- 
able, as  partial  admission  can  be  adopted.  By 
this  means  the  diameter  of  the  wheel  may  be 
increased  and  its  rotative  speed,  which  in  very 
high  falls  would  tend  to  become  excessive, 
reduced  in  proportion.  Another  feature  of 
the  impulse  turbine  is  that  its  efficiency  is 
practically  constant  throughout  all  degrees  of 
admission.  When  the  last  consideration  is 
unimportant,  the  Pelton  wheel  is  very  suitable 
for  high  falls.  (See  "  WATEK  POWER,  WATER 
WHEELS.")  E.  L.  B. 

Typhoid  Fever. — This  disease  appears 
to  affect  all  communities,  and  is  especially 
prevalent  in  urban  districts  with  impure 
water  supplies  and  imperfect  sewerage  systems. 
Fewer  cases  occur,  in  proportion  to  the  popu- 
lation, in  rural  districts,  even  where  the  water 
is  notoriously  impure  and  where  sanitary 
conditions  generally  are  unsatisfactory.  The 
explanation  doubtless  is  that  amongst  the 


more  scattered  population  the  risks  of  per- 
sonal infection  are  far  less  than  in  the  more 
densely  populated  towns.  .  The  disease  has  a 
marked  tendency  to  increase  in  prevalency 
during  the  autumn,  and  if  for  any  reason 
several  cases  have  occurred  in  the  summer 
quite  an  outbreak  may  occur  later  when  the 
season  is  more  favourable  for  its  spread.  The 


FlG.  4. — Method  of  fixing  "  Little  Giant"  Turbine. 

cause  of  these  autumnal  outbreaks  has  not 
yet  been  discovered.  The  infecting  agent  is 
a  bacillus  which  can  be  cultivated  outside  the 
human  body,  but  which  is  somewhat  difficult 
to  recognise  and  exceedingly  difficult  to  isolate 
when  associated  with  the  bacteria  found  in 
sewage.  In  fact,  it  is  not  always  possible  to 
find  it  in  water  which  may  be  known  to  be 
causing  disease.  The  bacilli  can  frequently 
be  discovered  in  the  blood  of  persons  suffering 
from  typhoid  fever,  but  they  are  far  more 
numerous  in  the  urine  and  faeces  at  certain 
stages  of  the  disease.  Recent  researches  have 
shown  that  in  some  instances,  which  may  be 
far  more  numerous  than  we  surmise,  the  faeces 
may  retain  the  bacilli  many  years  after 
recovery  from  an  attack.  Such  persons 
are  called  typhoid  "  carriers,"  and  several 
epidemics  in  public  institutions  and  numerous 
isolated  cases  have  been  traced  to  these 
"carriers."  From  the  urine  or  faeces  the 
bacilli  reach  the  drains  and  the  sewers,  and 
the  most  recent  research  has  proved  that  if 
there  is  any  splashing  in  such  sewers,  or  any 


M.S.E. 


481 


1 1 


TYP 


ENCYCLOPEDIA   OF 


TYP 


stagnation   leading   to    putrefaction  and  the 
bursting  of    bubbles  of   gas,  bacilli  are  dis- 
charged into  the  air,  and  may  be  detected  at 
the  ventilating  openings.    No  doubt  also  when 
infected  slops  are  thrown  over  badly  paved 
gullies  the  bacilli  may  get  into  the  air   and 
infect   water,   milk,   or   articles   of   food.     A 
typhoid    carrier    of    uncleanly    habits    may 
spread   the   disease   wherever   he    goes,   but 
unless  some  article  of  food  or  drink  used  in 
common   by  a   large   number   of  persons   is 
infected   the    cases   will    not    be    numerous. 
When  such  infection  does  occur  an  epidemic 
may  follow.     Epidemics  are  generally  due  to 
infection   of   water,   milk,   or    shell-fish ;    but 
some  occur  which  cannot  be  definitely  attri- 
buted to  these  causes.    Such  outbreaks  usually 
commence  in  the  autumn  and  follow  a  series 
of    isolated    cases.     Usually  also  it  is  found 
that  they  are  associated  with  grossly  insani- 
tary conditions,  uncleanliness,  overcrowding, 
defective    privies   or   water-closets,    defective 
drains  and  sewers,  fixed  uncovered   ash-pits, 
filthy   badly-paved    yards,    &c.      Taking    77 
recorded    outbreaks  which    have  occurred  in 
this  country  since    1881,   13  were  definitely 
traced   to  water,  in   17  instances   the  water 
was  gravely  suspected,  but  absolute  proof  was 
wanting,  in  4  milk  was  the  cause,  in  3  oysters, 
in  1  cockles,  and  in  1  watercress.      In    the 
remaining  38  cases  the  cause  could  not  be 
ascertained,  but  almost  invariably  the  sanitary 
circumstances   of   the   districts  invaded  were 
bad  in  the  extreme.     Water  outbreaks  would 
probably   be    more    numerous   were    it    not 
that  the  typhoid  bacillus  rapidly  dies  out  in 
that   medium.     Several   bacteriologists   have 
demonstrated  that  99*9%  of   the  bacilli  die 
within  7  days.     Where  a  water  has  been  pur- 
posely   and    largely    impregnated    with    the 
bacilli,    an    odd    bacillus    may    possibly    be 
discovered   for    many   days    afterwards,    but 
whether  these  more  resistant  organisms  are 
dangerous  or  not  there  is  no  means  of  ascer- 
taining.     This    fact,    however,    is    of    great 
practical   importance   as    showing    the   great 
advantage   of    storage,   but   whether   storage 
beyond  7  to  10  days  is  of  any  great  utility 


from  this  point  of  view  is  very  doubtful. 
Water  and  milk  outbreaks,  and  outbreaks  due 
to  infection  of  other  articles  of  food  or  drink, 
may  occur  at  any  period  of  the  year  and 
attack  all  classes  indiscriminately,  whilst 
outbreaks  due  to  unknown  causes  or  to 
insanitary  conditions  usually,  if  not  invariably, 
occur  in  the  autumn  and  affect  the  uncleanly 
and  the  poor  in  an  excessive  proportion. 
When  a  town  has  a  common  water  supply 
naturally  all  the  persons  attacked  will  have 
partaken  of  the  water,  but  unless  the  disease 
is  fairly  uniformly  distributed  throughout  all 
classes  and  throughout  the  town,  or  through- 
out an  area  supplied  by  a  particular  main, 
the  water  supply  cannot  be  the  cause.  If 
the  outbreak  is  localised,  or  only  occurs 
amongst  certain  classes,  and  especially  if 
limited  to  the  more  insanitary  areas,  some 
other  cause  than  the  water  must  be  sus- 
pected. Milk  may  be  infected  at  the  farm, 
or  the  dairy,  or  even  during  distribution  ; 
and  in  the  first  instance  nearly  all  the  patients 
will  be  consumers  of  the  implicated  milk, 
though  at  a  later  date  personal  infection  will 
commence.  So  far  as  is  known,  animals  do 
not  suffer  from  typhoid  fever,  and  there  is  no 
record  of  any  outbreak  having  occurred  from 
the  contamination  of  water  or  milk  by  animal 
manure.  The  bacilli  may  live  for  considerable 
periods  in  sand  and  soil,  or  on  dirty  surfaces, 
but  most  contradictory  results  have  been 
obtained  by  different  observers.  There  are 
reasons  for  believing,  however,  that  under 
very  favourable  circumstances  it  may  survive 
for  many  months  in  surface  soil.  It  is 
destroyed  in  a  few  minutes  by  a  temperature 
of  70°  C.  In  infected  urine  and  stools  it  may 
be  killed  by  a  very  liberal  use  of  disinfectants, 
allowed  to  act  for,  say,  an  hour  to  penetrate 
the  more  solid  matter. 

Although  it  is  doubtful  whether  it  can 
survive  even  a  few  hours  in  sewage,  it  is  now 
usual  to  supply  each  typhoid  patient,  not 
removed  to  an  isolation  hospital,  with  a  special 
pail  containing  disinfectants  for  the  reception 
of  the  urine  and  faeces.  These  are  changed  at 
regular  intervals  by  the  scavenger,  and  fre- 


482 


TYP 


MUNICIPAL   AND   SANITAKY   ENGINEEBING. 


UND 


quently  the  contents  are  mixed  with  sawdust 
and  petroleum  and  burnt.  Experiments  made 
with  the  common  house-fly  show  that  it  can 
convey  the  bacilli  on  its  feet,  and  that  these 
may  live  for  some  days  in  the  intestine  of  the 
insect  and  be  afterwards  found  in  the  spots 
of  faecal  deposit.  It  is  probable,  therefore, 
that  they  can  convey  infection,  and  one 
outbreak  attributed  to  infection  of  water 
cisterns  by  this  means  has  been  recorded. 

J.  C.  T. 

Typhus  Fever. — This  fever  was  for  a  long 
period  the  scourge  of  Europe,  but  during  the  last 
century  it  nearly  disappeared  from'  England, 
Wales,  and  Scotland.     Many  outbreaks,  how- 
ever, occurred  in  Ireland  during   periods  of 
famine.     Cases  still  occur  occasionally  in  our 
crowded  cities,  and  invariably  where  the  poor 
are  densely  aggregated  together  amidst  squalid 
surroundings.    It  is  one  of  the  most  contagious 
of  diseases,  more  frequently  than  any  other 
attacking  the  medical  attendant  and  nurses, 
or  those  coming  into  close  contact  with  the 
patient.     We   are   unfortunately  ignorant   of 
the  specific  cause,  but  there  is  every  reason  to 
believe  it  is  a  "  germ  "  disease.     Its  practical 
disappearance   is  due  to    many  causes ;    the 
improved  housing  of  the  poor,  diminution  of 
overcrowding,  greater  general  cleanliness,  and 
the  higher  standard  of  living.     When  an  out- 
break occurs  the  patients  should  be  promptly 
removed  to  an  isolation  hospital  or  other  place 
where  they  can  have  an  abundance  of  fresh  air. 
Contacts  should  be  carefully  watched  to  detect 
the  earliest  symptom  of  infection.     The  pre- 
mises infected  should  be  thoroughly  cleaned 
and  disinfected,  and  every  article  of  bedding 
or  clothing  which  has  been  used  by  the  patient 
should  be  sterilised  by  steam  or,  if  of  com- 
paratively little  value,  destroyed  by  fire.     If 
there  is  overcrowding  of   persons  in  houses, 
or  of  houses  on  space,  these  matters  should 
receive  attention.     If  cases  tend  to  occur  in 
the  same  locality  it  will  probably  be  found  to 
be  an  insanitary  area  requiring  clearing  and 
the  consideration  of  a  housing  scheme. 

J.  C.  T. 


Under- drainage. — The  object  of  under- 
drainage   is   to   keep   down   the  level  of  the 
subsoil  water,  so  that  the  soil  and  the  upper 
layers  of  the  subsoil  may  be  properly  aerated 
and  afford  a  proper  feeding  ground  for  the 
roots   of    the   crops.     The   need    for   under- 
drainage   is   greatest   with   clays  and   heavy 
loams,  and  in  districts  with  heavy  rainfalls. 
Open  sands  and  gravels,  on  the  other  hand, 
rarely  require  under-drainage ;  but  when  such 
land  is  to  be  irrigated  with  sewage  or  sewage 
effluent  it  should  generally  be  drained.  Various 
materials  have  been  used  for  under-drains ; 
unglazed  earthenware  pipes  with  butt  joints 
being  by  far  the  best.     The  size  of  the  pipes 
and  their  depth  and  distance  apart  will  depend 
on  the  nature  of  the  subsoil  and  on  the  rain- 
fall.    For  stiff  clays  2  in.  pipes  may  be  laid 
at  a  depth  of  3  ft.  and  in  lines  20  ft.  apart, 
while  in  a    gravelly  subsoil  2^  in.  or  3  in. 
pipes  will    be    required  at  a  depth   of    5  or 
6  ft.,  and  at  distances  as  great  as  80  or  100  ft. 
In  irrigated  land  the  spacing  will  generally  be 
closer,  and  the  size  of  the  pipes  should  not  be 
less  than  3  in.  or  4  in.     Larger  pipes  should^ 
of  course,  be  used  for  the  mains.     The  pipes, 
should  be  butted  tight  together,  and  in  filling 
the  trenches,  especially  in  irrigated  land,  care 
should  be  taken  to  consolidate  the  material  so 
that   the   water   may   not    take   a  short  cut 
through   it   from    the   surface   down   to    the 
pipes.     The    neglect   of    this    precaution    in 
many  cases  has  done  much  to  bring  under- 
drainage  into  disrepute.  A.  J.  M. 

Underground  Water.— Many  towns  de- 
pend for  their  water  supplies  upon  subter- 
ranean sources  obtained  by  means  of  sunk 
wells  or  borings.  Such  waters  accumulate 
through  percolation  of  rainfall  into  the  "  out- 
crop "  of  porous  strata  and  often  travel  many 
miles  underground  until  the  lowest  subter- 
ranean basin  is  reached.  Almost  any  porous 
formation  containing  fissures  or  "vents  "is 
capable  of  holding  large  quantities  of  water, 
especially  when  impermeable  strata  occur 
below.  Good  supplies  are  frequently  derived 
from  the  chalk,  new  red  sandstone,  oolite,, 


483 


n2 


UND 


ENCYCLOPAEDIA  OF 


UND 


magnesian  limestone,  Ashdown  sands  of  the 
Hastings  series,  and  other  porous  formations. 
It  should,  however,  be  understood  that  the 
quantity  obtainable  from  any  given  strata 
varies  considerably  in  different  situations 
according  as  the  rock  into  which  the  boring 
or  well  is  sunk  proves  to  be  compact  or  much 
fissured.  Chalk,  for  example,  is  one  of  the 
most  favourable  sources  from  which  water 
may  be  obtained,  but  even  this  in  some  cases 
has  proved  to  be  so  compact  as  to  yield  little 
or  no  supply.  Briefly  stated,  the  main  con- 
ditions determining  the  quantity  of  water 
obtainable  from  subterranean  sources  are  : — 
•(1)  The  mean  annual  rainfall  occurring  over 
the  "  catchment  area "  feeding  the  under- 
.ground  basin,  and  the  proportion  thereof 


Impermeable 
Stra£a, 


FIG-  i, — Conservation  of  Underground  Water  Supplies. 
percolating   in   at   the  "outcrop"   and   ulti-     district. 


mately  finding  its  way  to  the  subterranean 
store ;  (2)  the  extent  of  the  outcrop  of  the 
water-bearing  strata  and  the  degree  to  which 
the  slope  of  adjoining  inpervious  areas  may 
contribute  by  conducting  the  rainfall  falling 
thereon  on  to  the  porous  outcrop;  (3)  the 
area  of  the  underground  contributing  area  or 
watershed ;  (4)  the  degree  of  porosity  or 
permeability  of  the  water-bearing  strata,  and 
the  percentage  of  the  total  percolation  which 
is  again  recoverable  by  means  of  pumping 
stations ;  (5)  the  extent  to  which  artificial 
works  may  have  been  carried  out  for  the 
purpose  of  retaining  the  rainfall  upon  the 
catchment  area,  and  so  preventing  its  rapid 
escape  to  streams  and  rivers,  and  the  means 
adopted  to  intercept  the  flow  of  underground 
water  into  the  sea  or  river-beds.  Notwith- 
standing the  fact  that  underground  water  is 
very  largely  used  for  purposes  of  public  supply, 
but  little  attention  has  been  given  to  the 


question  of  the  conservation  of  subterranean 
water,  probably  owing  to  the  fact  that,  in  this 
country  at  any  rate,  underground  storage  is 
fairly  regularly  replenished  by  natural  means 
before  any  very  alarming  depletion  arises. 
It  is  also  difficult  in  the  majority  of  cases  to 
locate,  with  a  sufficient  degree  of  precision, 
the  most  favourable  site  and  nature  of  works 
likely  to  be  effective.  Where  suitable  condi- 
tions are  known  to  exist,  however,  the  quantity 
of  water  recoverable  may  be  augmented  by 
methods  similar  in  principle  to  those  illus- 
trated in  Fig.  1.  Here  an  artificial  dam  or 
puddle  wall  is  employed  to  intercept  water 
flowing  through  permeable  beds  on  its  way  to 
the  sea  towards  which  the  water-bearing 
strata  "dips."  Water  is  also  conducted  on  to 
the  porous  outcrop  of  the  per- 
meable strata  by  means  of  a 
conduit  from  an  extensive  catch- 
ment area  or  adjoining  hillside. 
Much  information  as  to  the 
water-bearing  capacity  of  any 
given  locality  is  obtainable  from 
a  careful  study  of  the  detailed 
geology  of  the  surrounding 
The  most  practical  means  of  doing 
by  first  collecting  particulars  of 
all  local  borings  or  wells,  the  levels  of  the 
different  strata  passed  through,  and  the  rest 
and  pumping  levels  of  the  water  in  such 
borings.  These  data  should  be  utilised,  with 
the  assistance  of  reliable  geological  maps  of 
the  district,  for  the  purpose  of  building  up  an 
accurate  section  of  the  strata  in  the  manner 
illustrated  in  Fig.  2,  which  diagrammatically 
represents  a  case  investigated  by  the  present 
writer  for  public  water  supply  purposes.  The 
section  covers  a  stretch  of  country  about 
14  miles  in  length,  the  surface  levels  of 
which  were  obtained  from  ordnance  maps, 
whilst  the  levels  of  the  different  strata  shown 
were  derived  from  various  borings,  three  of 
which  are  given  in  the  figure.  Upon  care- 
fully plotting  to  scale  all  available  informa- 
tion and  reducing  all  levels  to  ordnance 
datum,  it  was  found  the  rest  levels  of  water 
in  all  the  borings  coincided  very  closely, 


this    is 


484 


UND 


MUNICIPAL   AND    SANITAKY  ENGINEEEING. 


URI 


showing  the  water-bearing  sand-rock  to  take 
the  form  of  a  wide  basin  some  12  miles 
across,  and  to  be  uniformly  saturated  up  to 
the  level  shown.  The  section  also  revealed 
the  fact  that  a  well  or  boring  placed  at  A 
would  be  favourably  situated  for  yielding  a 
strong  supply  of  water,  which,  on  being 
tapped  upon  reaching  the  sand-rock  at  the 
depth  of  200  ft.  from  the  surface  at  once  rose 
in  the  boring  under  an  artesian  head  of 
100  ft.  The  great  importance  of  the  study 
of  practical  economic  geology  has  long  been 
appreciated  by  the  Geological  Survey  Office 
which  has  given  much  attention  to  the  ques- 
tion of  underground  water  supply,  and  has 


Outcrop 
of  fissured  sandrock 


qualities  appropriate  means  must  be  adopted 
to  properly  prepare  the  water  for  the  ordinary 
requirements  of  domestic  and  trade  supply. 

W.  H.  M. 

Urinals,  Public,     (See  "  CONVENIENCES.") 

Urinals,  amongst  sanitary  fittings,  are  the 
most  difficult  to  keep  in  a  wholesome  condition 
owing  to  the  urea  contained  in  urine,  which 
decomposes  very  rapidly,  and  the  uric  acid 
which,  being  but  feebly  soluble  in  water,  is 
very  liable  to  adhere  to  all  surfaces  with 
which  it  comes  in  contact.  Even  the  best  of 
these  fittings  are  frequent  sources  of  nuisance, 


Outcrop 

of  fissured  sruidrcck 


FIG.  2. — Section  of  Water-bearing  Data,  ascertained  from  Data  on  various  Borings. 


accumulated  a  large  amount  of  information 
upon  the  subject.  The  data  so  collected  is 
now  being  made  accessible  to  the  public  by 
the  publication  of  a  series  of  "  memoirs " 
dealing  with  the  underground  water  supply 
and  well  borings  of  different  counties,  and  the 
approximate  yield  available.  Underground 
water  is  usually  of  great  organic  purity,  but 
its  composition  naturally  depends  very  largely 
upon  the  nature  of  the  strata  through  which 
it  has  percolated.  It  is  commonly  highly 
charged  with  mineral  constituents,  and  not 
infrequently  of  great  "  hardness,"  a  large  part 
of  the  latter  quality  oftentimes  being  "  per- 
manent." Very  "  soft"  waters  are  also  some- 
times met  with,  and  in  some  cases  the  supply 
will  be  highly  charged  with  iron  either  in 
solution  or  suspension.  For  all  these  varying 


and  for  this  reason  urinals  are  best  avoided 
within  dwelling-houses.  Nor  are  they  essen- 
tial in  such  positions,  as  their  place  may  well 
be  taken  by  the  water-closets.  Where  the 
necessity  exists,  only  the  most  efficient  fittings 
must  be  provided.  The  following  conditions 
are  essential  in  urinals  : — (1)  The  soiling  sur- 
faces with  which  the  urine  comes  in  contact 
must  be  as  small  as  possible  consistent  with 
convenience ;  (2)  there  must  be  an  entire 
absence  of  angles,  corners,  and  unevenness 
that  would  tend  to  retain  deposits  of  urine  or 
of  dirt ;  (3)  the  materials  of  which  the  fittings 
are  made  must  be  smooth,  impervious  and 
incapable  of  being  acted  on  by  uric  or  other 
acids;  (4)  an  abundant  supply  of  flushing 
water  applied  each  time  the  urinal  is  used ; 
(5)  thorough  ventilation,  abundant  light,  and 


485 


VAL 


ENCYCLOPEDIA   OF 


VEN 


a  cool   atmosphere  in  the  urinal  apartment. 
(See  also  "  CONVENIENCES,  PUBLIC.") 

Valves.     (See  "  PUMPS.") 

Valves  (Water  Supply). — Cocks  or  taps 
fitted  with  a  loose  valve  or  diaphragm  acted 
upon  by  a  screw  spindle  with  handle  or  wheel. 
In  screwing  down  the  spindle,  the  valve  is 
forced  down  upon  its  seating  and  the  water 
gradually  shut  off.  When  unscrewed,  the 
pressure  of  water  forces  the  valve  off  its  seat 
in  some  cases,  while  in  others  the  spindle  raises 
the  valve,  leaving  the  water  free  to  flow 
through  in  either  case. 

Valves  may  be  divided  into  "  stop  valves  " 
placed  on  a  pipe  to  regulate  or  shut  off  the 


Screw-down  Valve. 

supply  of  water  and  "draw-off  valves  "made 
use  of  over  sinks  and  other  fittings  for  drawing 
water.  A  subdivision  of  the  latter  are  "  spring 
valves  "  so  constructed  that  water  can  only 
be  drawn  when  the  valve  is  held  open  by 
pressure  of  the  hand.  When  released  the  tap 
is  closed  automatically  by  a  spring.  Of  these 
only  those  that  close  gradually  and  without 
concussion  should  be  made  use  of  when  the 
water  is  under  pressure.  The  spindles  of  all 
valves  should  be  made  of  gun-metal,  but  all 
other  parts  may  be  of  hard  brass.  The  valves 
themselves  must  be  fitted  with  washers  of  oil- 
dressed  leather  and  for  hot  water  with  vege- 
table fibre  of  the  best  quality,  unless  they  are 


metal-faced  as  in  the  case  of   Lord  Kelvin's 
tap. 

Varnish. — Considered  generally  varnish 
may  be  defined  as  being  made  from  a  fossil 
resin  dissolved  with  heat  in  linseed  oil  or 
turpentine,  but  such  a  definition  must  neces- 
sarily be  vague  and  there  is  no  possible 
manner  of  specifying  varnishes  except  by  the 
name  of  the  manufacturer  or  by  the  price.  There 
are  many  grades  of  varnishes  ranging  from 
"  white  Coburg  varnish  "  or  "  body  varnish," 
costing  from  24s.  to  32s.  per  gallon  down  to  the 
cheapest  varnishes  which  may  be  had  as  low 
as  8s.  per  gallon,  or  less.  The  classification 
of  varnishes  in  general  is  roughly  as  follows  :— 
"white  marble  varnish,"  "white  oil  varnish," 
"white Coburg  varnish,"  and  "body  varnish," 
"  French  oil  varnish,"  "  white  copal,"  and 
the  best  "  carriage  varnish,"  range  from 
18s.  to  24s.  per  gallon.  "Maple  varnish." 
"  extra  pale  copal  varnish,"  "flatting  varnish," 
and  "  second  grade  carriage  varnish,"  range 
from  12s.  to  16s.  per  gallon.  "  Copal  oak 
varnish"  can  be  had  at  10s.,  and  second  grade 
of  the  same  at  8s.  Also  may  be  added  black 
varnishes  or  "  Japans,"  as  they  are  sometimes 
called,  which  are  sold  at  from  10s.  to  20s.  per 
gallon,  and  are  specially  suitable  for  iron- 
work. Enamels  come  under  the  same  cate- 
gory of  varnish  and  vary  very  largely  in 
quality,  costing  from  10s.  or  less  to  £1  Is. 
per  gallon.  (See  "  ENAMELS.") 

Velocity  of  Flow.    (See  "FLOW  IN  PIPES.") 

Ventilation  of  Buildings. — Amount  of  Air 
Eequired — Natural  Ventilation — Artificial  Ven- 
tilation— Cottages — Public  Halls. — Pure  air  is  as 
essential  to  human  life  as  good  food,  although 
the  fact  is  not  fully  appreciated,  and  before 
proceeding  to  deal  with  ventilation  schemes  it 
will  be  as  well  to  study  briefly  the  composition 
of  the  air. 

The  following  table  gives  the  proportions  of 
an  average  sample  of  air  taken  by  Parkes  :— 


Oxygen 

Nitrogen 


209-6  per  1,000  volumes. 
790-0    , 


486 


YEN 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


YEN 


0'4  per  1,000  volumes. 
Varies  with  temperature. 
Trace. 


>•  Variable. 


Carbonic  acid 

Watery  vapour 

Ammonia 

Organic  matter  (in  vapour 
or  suspended,  organised, 
unorganised,  dead  or 
living) 

Ozone 

Salts  of  sodium 

Other  mineral  substances .  . 


OXYGEN  is  the  chief  constituent  of  air,  and 
the  great  purifier  of  air,  as  well  as  the  princi- 
pal aid  in  combustion.  It  is  upon  this  gas 
that  the  heat  and  energy  of  our  bodies 
depend. 

CARBONIC  ACID. — Among  the  impurities  in 
air  this  is  probably  the  greatest.  The  late  Sir 
Douglas  Galton  stated  that  1'5  parts  per  cent, 
produce  nausea,  depression,  and  headache  ; 
2*5  %  extinguishes  a  candle,  and  5  parts  per 
cent,  is  fatal.  It  will  be  evident  from  this  that 
systems  of  ventilation  must  be  such  as  will 
reduce  this  dangerous  element  to  a  minimum. 
The  amount  generally  allowed  as  a  safe  quan- 
tity is  '6  per  1,000  cu.  ft.  The  burning  of  gas 
in  houses  and  factories  is  a  great  defaulter  in 
polluting  the  air,  and  it  has  been  found  that 
1  cu.  ft.  of  gas  will  consume  the  entire  oxygen 
of  8  cu.  ft.  of  air,  in  addition  to  imparting 
impurities  in  the  form  of  compounds  of  sulphur 
and  carbon.  The  effect  of  impure  air  on  the 
system  is  very  detrimental,  producing  a 
lowering  of  the  vital  functions,  and  thus 
tends  to  the  contraction  of  disease  and  pro- 
longs the  period  of  recovery. 

QUANTITY  OF  AIR  REQUIRED. — It  has  been 
found  that  an  average  adult  gives  off  by  res- 
piration '6  cu.  ft.  of  carbonic  acid  (COa)  per 
hour.  By  referring  back  to  the  table  giving 
the  composition  of  the  air  we  find  air  contains 
•4  cu.  ft.  of  carbonic  acid  per  1,000  ft.  By 
adding  this  amount  to  that  given  off  by  respira- 
tion a  total  of  I'O  cu.  ft.  of  carbonic  acid 
per  1,000  cu.  ft.  of  air  is  obtained.  This 
is  more  than  has  been  laid  down  as  the 
standard,  viz.,  '6  cu.  ft.  per  1,000  cu.  ft.  of 
air.  The  amount  of  air  required  per  person 
per  hour  is  3,000  cu.  ft.,  and  the  air  of  rooms 


should  be  changed  with  sufficient  frequency, 
according  to  their  size,  to  maintain  that 
standard.  This  changing  of  the  air  is  a 
matter  requiring  careful  attention,  in  order 
not  to  give  rise  to  draughts.  Air  which  moves 
at  a  greater  velocity  than  2  ft.  per  second 
will  cause  draughts,  and  the  system  must  be 
so  arranged  that  this  velocity  will  not  be 
exceeded.  The  above  amount  of  3,000  cu.  ft. 
of  air  per  person  per  hour  is  an  ideal  state, 
and  in  practice  it  is  found  difficult  to  reach 
that  standard.  The  usual  amount  in  cottages 
is  about  250  cu.  ft.  per  person — e.g.,  if  we 
take  a  small  room  of  10  ft.  by  10  ft.  and  8  ft. 
high  we  get  800  cu.  ft.,  but  allowance  must  be 
made  for  furniture,  which  will  occupy  about 
100  cu.  ft.,  and  if  the  room  is  occupied  by 
three  persons  this  gives  230  cu.  ft.  per  person. 
The  following  table  extracted  from  different 
sources,  including  the  model  by-laws  of  the 
Local  Government  Board,  will  give  an  idea  as 
to  what  is  generally  required  : — 


Houses  let  in  lodgings . 


Dairies,  &c. 

Factories  and  workshops 


Schools    (Education 

Department) 
Public  Halls 

Hospitals  (ordinary)     .  . 
,,          (infectious)  . . 


150  cu.  ft.  per  person  under 
10  years  of  age. 

300  cu.  ft.  for  adults  for 
sleeping  only. 

200  and  400  cu.  ft.  respec- 
tively for  rooms  when  not 
used  for  sleeping  pur- 
poses. 

600  cu.  ft.  per  cow. 

250  cu.  ft.  per  person. 

400  cu.  ft.  per  person  for 
overtime. 

80  cu.  ft.  per  head.1 

1,200  -  1,500    cu.    ft.     per 

head.1 

1,200  cu.  ft.  per  head.1 
2,100  -  3,000    cu.    ft.     per 

head.1 


It  is  a  mistake  to  imagine  that  lofty  rooms 
take  the  place  of  air  space.  The  amount  of 
space  available  for  ventilation  purposes  should 
be  taken  at  a  height  of  not  less  than  12  ft. 
and  not  more  than  13  ft.  There  are  two 

1  "  Architectural  Hygiene,"  B.  F.  Fletcher,  p.  146 
(1902). 

487 


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ENCYCLOPEDIA   OF 


VEN 


methods  of  ventilation :  (1)  natural,  and 
(2)  artificial.  It  is  proposed  to  deal  with  the 
principles  and  different  appliances  that  are 
used  in  each  system.  It  is  impossible  to  carry 
out  an  efficient  system  of  ventilation  without 
having  due  regard  to  the  allied  questions  of 
heating  and  lighting,  and  the  reader  is  referred 
to  the  articles  dealing  with  these  subjects,  as 
it  is  important  to  know  how  to  utilise  these 
two  essential  factors  in  any  scheme  pf 
ventilation. 

The  forces  which  tend  to  move  the  air  in 
rooms  are  two  :  (1)  the  wind,  (2)  the  difference 
in  temperature  between  the  outside  air  and 
that  in  the  room.  The  wind  is  a  great  factor 
in  ventilation,  and  causes  the  air  to  move 
rapidly.  Cold  air  is  heavier  than  hot  and 
upon  entering  a  room  falls  to  the  bottom,  dis- 
placing the  hot  air  in  the  room.  If  the 
incoming  air  is  unwarmed  before  it  enters,  it 
causes  a  draught  and  the  inlet  is  closed  by  the 
occupants.  The  following  table  compiled  by 
Scott  &  Co.  gives  the  powers  of  fans  manu- 
factured by  them,  and  will  be  useful : — 


FOUL  AlR  EXTRACTED  UNDER  CERTAIN  HEADS  OF 

WATER. 
24  in.  fan. 

Water    pressure,     Ibs.     per 
sq.  in  ....... 

Air  per  min.,  approx.  cu.  ft. 
Revolutions  per  min.,  approx. 
Water  per  hour,  gallons  .  . 

|  in.  supply. 
18  in.  fan. 

Air  per  min.,  approx.  cu.  ft. 
Revolutions  per  min.,  approx. 
Water  per  hour,  gallons     .  . 
i  in.  supply. 


60       50  40        30 

4,000  3,000  2,000  1,000 

500      350  220      150 

120      100  60 
in.  drain. 


45 


2,000  1,500  1,000 
650   450   300 
90   60   50 
in.  drain. 


800 
200 
40 


For  many  purposes  water-driven  fans  would 
be  unsuitable  and  electricity  may  be  conveni- 
ently used.  Messrs.  Blackman  make  fans 
which  are  extensively  used  for  this  purpose, 
and  for  long  buildings  where  the  rooms  are 
scattered  and  numerous,  the  "  Guibal  "  type 
of  fan  appears  to  be  the  best. 

NATUKAL  VENTILATION. — This,  as  its  term 
implies,  means  the  conveyance  of  fresh  air 


into  the  buildings  by  natural  methods,  such  as 
ordinarily  occurs  through  doors,  windows, 
fireplaces,  &c.  As  previously  pointed  out  the 
forces  necessary  in  this  system  are  the  wind 
and  the  difference  in  temperature,  between 
the  outside  and  the  inside  air. 

INLET  AND  OUTLET  TUBES. — When  bringing 
in  the  air  by  tubes,  they  must  be  arranged  to 
have  as  few  sharp  bends  as  possible,  as  these 
greatly  diminish  the  carrying  power  of  the 
tube.  Allowances  must  also  be  made  for 
friction  when  calculating  the  size  of  the  tubes 
to  be  used  in  the  ventilation  of  rooms.  They 
must  be  large,  smooth  inside,  free  from  bends, 
and  vertical  and  short  as  far  as  possible,  and 
preferably  circular  in  shape.  The  joints  of 
the  tubes  must  be  thoroughly  air-tight.  The 
position  of  the  openings  must  be  carefully 
considered,  as  the  cold  air  should  not  be 
allowed  to  fall  directly  into  the  room  before 
it  is  slightly  warmed.  The  height  of  air 
inlets  above  floor  level  generally  adopted  in 
practice  is  from  5  to  6  ft.,  preferably  the 
latter. 

The  size  of  the  inlets  should  be  proportional 
to  the  number  of  persons  occupying  the  room, 
and  Dr.  Corfield  recommends  that  24  sq.  in. 
sectional  area  be  allowed  for  each  person.  In 
calculating  the  sizes,  the  net  opening  only 
must  be  taken,  and  due  allowance  made  for 
bars,  &c.,  obstructing  the  opening. 

Hood  has  given  the  following  table  for 
finding  the  sizes  of  the  opening,  taking  into 
consideration  the  number  of  persons  and 
lights,  and  size  of  the  room : — 


Size  of  Room. 

Number  of 
Occupants. 

Number  of 
(ias-burners. 

Net  Size  of 
Ventilator. 

10  ft.  by  10  ft. 
16  ft.  by  12  ft. 
20  ft.  by  16  ft. 

2  or  3 
3  or  4 
4  or  5 

2 
3 
4 

9  in.  by  3  in. 
9  in.  by  6  in. 
9  in.  by  9  in. 

The  outlet  must  be  in  a  high  position,  and 
as  the  warmest  and  foulest  air  is  always  at 
the  top  of  the  room,  near  the  ceiling,  the 
outlet  should  be  in  that  position.  The  aggre- 


488 


VEN 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


VEN 


gate  area  of  the  inlets  should  be  somewhat  in     Important  features  in  the  system  are  (1)  the 


excess  of  that  of  the  outlets,  and  the  inlets 
should  be  placed  as  far  away  as  possible  from 
the  outlets,  so  as  to  insure  a  thorough  cir- 
culation of  the  air  in  the  room. 

SYSTEM  OF  BOYLE'S  VENTILATION  FOE 
INFECTIOUS  HOSPITALS.  —  Boyle's  system  of 
Ventilation  for  Infectious  Hospitals,  as 
described  by  the  Building  News,  May  26th, 
1899,  is  as  follows  : — 

"  This  appliance,  which  Mr.  Boyle  has 
named  '  Bactolite,'  is  intended  to  be  employed 
in  small-pox  and  other  infectious-diseases 
hospitals  .  .  .  destroying  the  disease  germs 
contained  in  the  air  of  an  hospital,  as  it 
passes,  or  rather  is  drawn,  through  an 
asbestos  furnace  situated  in  the  roof,  and 
connected  with  an  '  air-pump  '  ventilator, 
effectually  consuming  the  poisonous  germs, 
and  preventing  them  from  passing  into  and 
contaminating  the  outer  air  and  spreading 
infection. 

"  With  the  '  Boyle'  system  of  ventilation,  as 
applied  to  small-pox  hospitals,  the  air  inlets 
communicate  direct  with  the  external  air 
through  specially-constructed  openings  made 
in  the  walls,  fitted  with  self-acting  valves  to 
prevent  the  air  of  the  hospital  passing  by  any 
chance  out  through  these  openings.  The 
incoming  air  is  warmed  in  cold  weather  to  an 
agreeable  and  healthy  temperature  by  means 
of  Boyle's  ventilating  radiators,  without  the 
deterioration  and  discomfort  which  result  from 
hot-air  heating. 

"Am  SCREENS. — In  warm  weather,  the  fresh- 
air  supply  is  cooled  in  its  passage  through 
adjustable  refrigerating  chambers  attached  to 
the  radiators,  and  is  washed  and  purified  by 
filtration  through  saturated  and  medicated 
screens.  The  outlets  and  inlets  are  accessible 
in  all  parts  for  cleansing  purposes.  It  would 
appear,  from  the  tests  which  have  been  made 
by  scientific  experts,  that  air-screens  are  more 
effective  when  the  air  is  drawn  through  at  a 
low  velocity  by  natural  extraction  than  with 
mechanical  propulsion.  Sir  Douglas  Galton 
says  :  '  If  air  is  forced  rapidly  through  a 
screen,  it  cannot  fail  to  carry  dust  with  it.' 


fresh  air  is  brought  directly  into  the  room 
from  the  external  air,  there  being  no  long, 
tortuous,  and  inaccessible  channels  to  harbour 
dust  and  dirt ;  (2)  the  air  supply  not  being 
overheated,  its  health-sustaining  properties 
are  unimpaired.' ' 

ARTIFICIAL  VENTILATION. — This  system 
depends  for  its  working  upon  mechanical 
means  for  propelling  air  into,  or  extracting 
foul  air  from  the  room  or  rooms.  It  is  divided 
into  two  systems,  plenum  and  vacuum.  The 
former  method  is  that  in  which  air  is  pro- 
pelled into  the  rooms  by  fans  or  air  pumps, 
thus  forcing  out  the  foul  air.  The  vacuum 
system  consists  of  extracting  the  foul  air  by 
means  of  furnaces,  gas  jets,  fans,  or  exhaust 
pumps,  and  allowing  the  fresh  air  to  enter  to 
take  its  place. 

With  regard  to  the  admission  of  the  cold 
air  from  the  outside,  this  should  be  brought 
in  at  a  point  above  the  people's  heads  and 
in  an  upward  direction.  It  then  becomes 
slightly  heated  before  descending,  but  not 
warm  enough  to  allow  the  already  heated  air 
to  stay  in  the  room. 

The  only  methods  which  appear  satisfactory 
in  large  buildings  are  those  involving  propul- 
sion or  extraction  by  fans.  The  air  thus  pro- 
pelled should  be  first  brought  through  a 
heating  chamber  if  only  for  one  room,  and  if 
for  a  number  of  rooms  should  be  brought  over 
a  series  of  heated  coils  (see  ARTIFICIAL  VENTILA- 
TION below). 

One  of  the  largest  installations  of  ventilation 
on  the  "plenum"  system  is  that  introduced 
into  the  Birmingham  General  Hospital,  by 
Mr.  Kenman,  F.R.I.B.A.,  and  is  described  in 
"  Architectural  Hygiene,"  by  B.  F.  and  H.  P. 
Fletcher  (1907),  p.  189,  as  follows  :— "  .... 
No  fireplaces  are  used,  the  air  being  forced  in 
by  fans,  cleansed,  and  brought  to  a  proper 
hygrostatic  condition  by  filtering  through 
moistened  screens,  warmed  when  required  by 
means  of  steam  coils,  and  propelled  through 
the  wards  into  extract  flues,  whence  it  passes 
into  the  open  through  flapped  and  louvred 
openings,  constructed  so  that  the  varying 


489 


YEN 


ENCYCLOPEDIA   OF 


VEN 


movements  of  the  outer  atmosphere  can  exert 

no  influence  upon  the  outflow The  air 

is  sucked  in  from  windows  in  the  basement 
(carefully  selected  so  as  to  be  out  of  the  way 
of  contaminated  air)  by  a  fan,  passing  first 
through  a  screen  of  strained  cocoanut  fibre, 
kept  automatically  wetted  every  quarter  of  an 
hour.  The  air  is  then  carried  through  a 
series  of  horizontal  steam  pipes,  heated  to  the 
required  temperature,  then  through  the  fan 
and  into  the  basement  tunnels.  These  tunnels 
(or  "  ducts "  as  they  are  called)  start  in 
sectional  area  11  ft.  by  8  ft.,  and  only  in  a 
few  cases  are  they  so  little  as  3  ft.  in  width  at 
the  extreme  ends  in  a  few  branch  ducts. 
From  these  ducts  are  taken  the  vertical  ducts 
to  the  rooms  above.  At  the  mouth  of  each  of 
these  vertical  ducts  is  a  separate  steam  radiator 
to  give  extra  warmth  if  required  for  different 
departments,  in  excess  of  that  supplied  by  the 
main  collection  of  steam  coils."  The  foul 
air  is  forced  into  the  outlet  flues  at  the  bottom 
of  the  room  near  the  floor  level.  In  the 
example  above  quoted,  to  insure  success  in 
the  working  of  the  scheme,  all  the  windows 
are  hermetically  sealed.  The  reader  may 
judge  for  himself  as  to  the  success  after  read- 
ing the  following  extract  from  an  article  in 
The  Hospital,  April  1st,  1899,  commenting  on 
a  visit  to  the  above  hospital : — "  ....  The 
visit  in  question  was  paid  with  an  open  mind, 
and  in  conjunction  with  others  anxious  to 
observe  in  practice  a  previously  carefully 
studied  theory.  .  .  .  The  point  most  generally 
commented  upon  was  the  apparently  unnatural 
stillness  of  the  atmosphere,  whereas  the  air 
was  being  much  more  rapidly  changed  than 
is  usual.  ...  It  seems  that  this  subjective 
sensation  is  almost  invariably  experienced  by 
newcomers  to  the  hospital,  though  both  nurses 
and  patients  gradually  become  accustomed  to 
what  scientists  assert  should  be  a  natural  (but 
which  to  most  of  us  at  present  appears  to  be 
a  somewhat  artificial)  atmosphere.  It  has 
been  stated  that  this  feeling  of  oppression 
does  not  meet  with  the  entire  approval  of  the 
visiting  staff,  as  exercising  upon  them  an 
indefinably  depressing  effect.  The  atmosphere 


of  those   wards   visited   struck  the  party  as 
somewhat  close,  lacking  in  freshness.  .  .  ." 

The  opinions  of  many  authorities  appear 
to  be  strongly  opposed  to  propulsion  of 
fresh  air  into  rooms,  and  the  following 
extract  from  a  report  laid  before  the  United 
States  Congress  by  the  Government  Com- 
mission on  Ventilation  will  be  of  interest. 
"  The  relative  merits  of  the  upward  versus 
the  downward  systems  of  ventilation  may  be 
estimated  from  the  following  considerations  :— 
(1)  The  direction  of  the  currents  of  air  from 
the  human  body  is,  under  ordinary  conditions, 
upwards,  owing  to  the  heat  of  the  body.  This 


FIG.  1. — Movement  of  Air  in  a  Room  with 
ordinary  Fireplace. 

current  is  an  assistance  to  upward,  and  an 
obstacle  to  downward,  ventilation.  (2)  The 
heat  from  all  gas  flames  used  for  lighting 
tends  to  assist  upward  ventilation,  but  elabo- 
rate arrangements  must  be  made  to  prevent 
contamination  of  the  air  by  the  lights  if  the 
downward  method  be  adopted.  (3)  In  large 
rooms  an  enormous  quantity  of  air  must  be 
introduced  in  the  downward  method  if  the 
occupants  are  to  breathe  pure  fresh  air,  or 
about  three  times  the  amount  which  is  found 
to  give  satisfactory  results  with  the  upward 
method.  (4)  In  halls  arranged  with  galleries, 
the  difficulty  of  so  arranging  downward 
currents  that,  on  the  one  hand,  the  air  rendered 
impure  in  the  galleries  shall  not  contaminate 


490 


VEN 


MUNICIPAL   AND    SANITARY   ENGINEERING. 


VEN 


that  which  is  descending  to  supply  the  main 
floor  below,  and,  on  the  other  hand,  the  supply 
for  the  floor  shall  not  be  drawn  aside  to  the 
galleries,  is  so  great  that  it  is  almost  an 
impossibility  to  effect  it.  Perfect  ventilation 
would  not  be  obtained,  for  this  would  only 
provide  for  the  dilution  of  the  impure  air, 
while  in  perfect  ventilation  the  impurities  are 
not  so  diluted,  but  completely  removed  as  fast 
as  formed,  so  that  no  man  can  inspire  any 
air  which  has  shortly  before  been  in  his  own 
lungs  or  in  those  of  his  neighbour.  For 
these  and  other  reasons  the  Board  are  of 
opinion  that  the  upward  method  should  be 
preferred." 


therefore  become  lurking  places  for  dust  and 
germs.      The  plan    is   quite   unsuitable    for 


FIG.  2. — Movement  of  Air  with  Dalton's  Fireplace. 

Dr.  John  Hayward,  in  a  paper  on  "  Hospital 
Construction,"  read  before  the  Liverpool 
Architectural  Society  on  November  7th,  1898, 
also  wrote  as  follows  :  —  "  To  the  plan  of 
abstracting  the  foul  air  near  the  floor,  there 
are  at  least  four  grave  objections :  (1)  It 
is  opposed  to  Nature's  laws  of  atmospheric 
pressure,  and  therefore  requires  the  use  of 
special  abstracting  power  by  means  of  furnaces 
for  its  accomplishment.  (2)  By  drawing  down 
the  foul  air  it  causes  it  to  be  breathed  over 
again,  which  recently  breathed  air  ought 
never  to  be.  (3)  The  fresh  air  supplied  is 
apt  to  be  forced  in  over-heated,  in  fact  burnt, 
and  so  made  unhealthy.  (4)  The  long 
tortuous  flues  cannot  be  kept  clean,  and  will 


FIG.  3.—  Sheringham  Valve. 

hospitals,  and  should  certainly  never  be  used 
where  there  is  likely  to  be 
infection.  Besides,  it  is  also 
open  to  the  same  objections  as 
ventilation  by  open  fires,  viz., 
that  it  tends  to  draw  away  the 
air  of  the  lower  part  of  the 
ward,  where  it  is  always  the 
least  impure." 

PRACTICAL  VENTILATION  OF 
VARIOUS  CLASSES  OF  BUILDINGS  : 
COTTAGES. — Fresh  air  is  gene- 
rally admitted  to  cottages 
either  by  air-bricks  or  per- 
forated gratings  or  other  patent 
ventilators.  These  should  be 
placed  high  up  in  the  room. 
A  flue  may  also  be  built  in 
the  chimney  to  admit  the  outside  air  and 
having  an  inlet  for  air  into  the  room  high  up 


FIG.  4. — The  "  Leather"  Inlet  Ventilator. 

in  the  chimney  breast,  the  cold  air  thus  being 
warmed  before  it  enters  into  the  room  (see 
Fig.  2). 


491 


VEN 


ENCYCLOPEDIA   OF 


VEN 


PUBLIC  HALLS.  —  The  inlets  for  air  may 
be  of  various  kinds  and  shapes.  Fig.  3  is  an 
illustration  •  of  the  Sheringham  valve,  and 
Figs.  4  and  5  are  illustrations  of  an  inlet 
valve  patented  by  Mr.  Leather,  of  Liverpool. 


FIG.  5. — Section.     Leather  Inlet  Valve. 

It  will  be  seen  that  the  adjustable  portion 
is  divided  into  four  compartments,  two 
of  which  are  covered  by  perforated  zinc. 
Fig.  6  is  an  illustration  of  an  inlet  tube 
of  the  "Tobin"  tube  type. 
These  are  formed  of  boarding 
and  lined  with  zinc,  or  made 
entirely  of  metal,  having  an 
adjustable  part  for  regulat- 
ing the  supply  of  air.  They 
are  in  some  cases  built 
in  chases  in  the  wall  (see 
Fig.  7).  Air  may  also  be 
brought  in  over  heating  coils 
or  radiators,  thus  being 
warmed  before  it  enters  the 
room  (see  Fig.  8).  Extrac- 
tion should  be  by  means  of 
a  fan  or  an  air-pump  venti- 
lator. 

FACTORIES  AND  WORKSHOPS. 
— Ventilation  in  these  build- 
ings is  comparatively  an  easy 
FIG.  6.  matter.    There  are,  however, 

several  important  points  to 
be  borne  in  mind,  and  different  methods 
must  be  adopted  for  different  trades.  Under 
the  Factory  and  Workshops  Act,  1901,  bake- 
houses are  classed  as  workrooms.  It  will 
be  impossible  to  deal  with  every  special  trade 
and  its  requirements  for  ventilation,  but  a  few 
will  be  touched  upon  briefly.  The  Factory 
and  Workshops  Act,  1901,  gives  the  following 


air-space  for  the  particular  factories  men- 
tioned :  —  General  Factories,  250  cu.  ft.  of 
fresh  air  per  person ;  400 
cu.  ft.  of  fresh  air  per 
person  (overtime). 

An  Order  gazetted 
February  llth,  1902, 
provides  for :  600  cu.  ft. 
of  fresh  air  per  person 
in  humid  textile  factories 
(other  than  cotton  cloth 
factories). 

An  Order  gazetted 
January  1st,  1904,  pro- 
vides for :  500  cu.  ft.  of 
fresh  air  per  person  in 
underground  bake- 
houses ;  400  cu.  ft.  in 
bakehouses  where  work 
is  carried  on  in  artificial 
light  other  than  electric 
light  between  9  P.M.  and 
6  A.M. 

For  cotton  cloth  fac- 
tories,      the       Factory 
and     Workshops      Act, 
1901,    s.    94,    states    that    ventilation    shall 
be    so    carried    out    that    during    working 


FIG.  8. 


hours    the   proportion    of    carbonic    acid    in 
the     air     shall     not     be     more     than    nine 


492 


VEN 


MUNICIPAL   AND   SANITAEY  ENGINEERING. 


VEN 


volumes  of  carbonic  acid  to  every  10,000 
volumes  of  air.  Strict  enforcements  are  laid 
down  for  these  and  other  humid  factories 
with  regard  to  temperature  and  moisture, 
and  architects  having  these  buildings  to 
design  and  superintend  should  refer  to  the 
1901  Act,  s.  90.  In  factories  where  dust  and 
other  fine  matter  is  produced  as  refuse  from 
manufactured  articles,  arrangements  must 
be  made  to  extract  it  by  means  of  exhaust 
fans,  so  that  the  fresh  air  coming  into  the 
workroom  or  factory  will  not  scatter  these 
particles  about.  All  windows  should  have 
some  portion  made  to  open.  Tobin  or 
similar  tubes  should  be  fitted  of  sufficient  size 
and  number  to  convey  the  required  quantity 
of  fresh  air  according  to  the  number  of  per- 
sons employed.  If  the  air  brought  in  must 
be  warmed  inlets  should  be  made  near  the 
floor  at  the  back  of  the  steam  warming  pipes. 
These  inlets  should  deliver  air  into  a  small 
closed-in  chamber  having  a  perforated  cover 
or  sides,  through  which  the  warm  air  will 
pass  into  the  room. 

Foul  air  may  be  extracted,  at  a  point  near 
the  ceilings,  either  by  means  of  an  exhaust 
fan,  or  by  openings  made  in  the  walls, 
covered  by  perforated  cast-iron  gratings,  of 
the  same  size  and  number  as  the  fresh  air 
inlets. 

E.  H.  B. 

Ventilation  (of  Sewers  and  Drains).— 

The  object  of  sewer  ventilation  is  to  regularly 
remove  the  gaseous  impurities  given  off  by 
the  decomposition  of  sewage  matters,  com- 
mencing immediately  upon  their  deposition, 
and  to  supply  fresh  atmospheric  air  from  the 
outside.  Sewer  air  ordinarily  contains  many 
impurities,  amongst  which  may  be  mentioned 
&  large  proportion  of  complex  hydro-carbon 
and  nitrogenous  vapours  derived  from  decom- 
posing animal  and  vegetable  matters,  consider- 
able carbonic  acid,  ammonia,  ammonium 
sulphide,  sulphuretted  hydrogen,  and  marsh 
.gas.  In  the  liquid  sewage  are  large  numbers 
of  bacteria  of  various  kinds,  and  these  break 
up  the  organic  matters  into  simple  chemical 


compounds,   and   gases   are    evolved    in   the 
process. 

The  bacteriological  contents  of  sewer  air  has 
been  the  subject  of  much  careful  investiga- 
tion. The  conclusions  arrived  at  in  1893  as 
the  result  of  an  investigation  on  behalf  of 
the  London  County  Council  were — (a)  that 
the  number  of  micro-organisms  in  sewer  air 
is  smaller  than  in  the  fresh  air  examined  at 
the  same  time ;  (b)  that  the  species  of  micro- 
organisms in  sewer  air  are  identical  with  those 
of  fresh  air,  and  not  with  those  of  sewage  ; 
(c)  that  moderate  splashing  does  not  influence 
the  bacterial  content  of  sewer  air,  even  within 
4  ft.  of  the  disburbance ;  and  (d)  that  stag- 
nant and  putrescent  sewage  does  not  influence 
the  organisms  in  sewer  air.  The  subject  was 
further  reported  upon  in  1894  by  Dr.  Andrewes 
and  Mr.  Laws,  when  they  were  unable,  by 
means  of  the  methods  of  research  then  avail- 
able, to  find  any  evidence  that  sewage  gives 
up  any  of  its  bacteria  to  the  air  in  contact 
with  it.  As  a  result  of  investigations  made 
up  to  that  period,  the  opinion  had  become 
general  that  under  ordinary  conditions  sewage 
does  not  contaminate  the  air  with  which  it  is 
in  contact  with  its  own  specific  bacteria,  but 
the  improvements  which  have  more  recently 
been  made  in  the  technique  appropriate  to 
an  inquiry  of  this  kind  has  now  warranted 
a  modification  of  these  opinions.  Dr.  F.  W 
Andrewes  in  his  "  Eeport  on  the  Micro- 
organisms present  in  Sewer  Air  and  the 
Air  of  Drains,"  which  appears  among  the 
appendices  of  the  report  of  the  medical  officer 
of  the  Local  Government  Board  for  1906 — 07, 
says,  "  Under  certain  circumstances,  at  all 
events,  sewage  gives  up  its  bacteria  to  sewer 
and  drain  air.  Such  bacteria  may  form  but  a 
small  proportion  of  those  present  in  sewer 
air  :  this  is  likely,  for  they  would  not  other- 
wise have  escaped  detection  by  previous 
observers.  But  it  is  probable  that  the  cir- 
cumstances under  which  sewage  gives  up  its 
bacteria  are  common  and  ordinary  circum- 
stances in  sewer  and  drain  construction,  for 
the  employment  of  selective  culture  media  has 
enabled  me  to  discover  them  wherever  so  far 


493 


VEN 


VEN 


looked  for  in  the  air  of  drains  and  sewers. 
.  .  .  The  importance  of  the  subject  is  plain, 
for  though  the  organisms  which  I  have  been 
able  to  detect  in  sewer  air  are  not  in  them- 
selves known  to  be  prejudicial  to  health,  being 
for  the  most  part  well-known  saprophytes  of 
the  normal  alimentary  tract,  yet  their  value 
is  evident  as  indices  of  the  possible  presence 
of  more  harmful  sewage-borne  microbes." 

The  typhoid  bacillus  does  not  thrive  well  in 
sewage,  and  their  death  is  probably  only  a 
matter  of  a  few  days,  or  at  most  one  or 
two  weeks.  Prolonged  inhalation  of  sewer 
air  may  prove  injurious  to  health  by  lowering 
the  vitality  of  the  human  system  and  so  pre- 
disposing to  disease ;  hence  the  importance  of 
keeping  the  air  from  sewers  and  drains  out  of 
inhabited  rooms,  both  by  adopting  sound 
sanitary  arrangements  and  also  by  thoroughly 
ventilating  dwellings  by  making  provision  for 
a  constant  circulation  and  .change  of  air. 

One  of  the  most  effectual  means  of  keeping 
the  air  of  sewers  as  pure  as  possible  consists 
in  laying  the  sewers  at  self-cleansing  velocities, 
and  in  maintaining  a  clean  and  smooth  bore. 
In  this  way  the  sewage  passing  through  them 
away  to  the  outfall  expeditiously  minimises  the 
opportunities  for  decomposition,  and  the  sewers 
are  kept  free  from  bad  air.  As  soon  as  septic 
action  sets  in  offensive  gases  are  evolved,  and 
the  air  of  sewers  becomes  very  foul. 

The  principal  methods  which  have  been 
adopted  for  the  ventilation  of  sewers  may  be 
shortly  summarised  as  follows : — 

(a)  Natural  ventilation  by  the  aid  of  open 
surface  gratings  at  the  road  level,  assisted  by 
iron  ventilating  columns  erected  along  the  line 
of  sewers,  or  by  carrying  ventilating  shafts 
up  the  flank  walls  of  buildings  and  other  avail- 
able places. 

(b)  Mechanical    ventilation,    by   means    of 
powerful  fans. 

(c)  Heat  extraction,  such  as  by — 

(1)  Connecting  sewers  with  chimney  shafts. 

(2)  Connecting  with  iron  on  other  shafts 
erected  along  the  lines  of  sewers,  each  of  such 
being   provided  with  heat   either  by  a   gas- 
burner  in  the  base  of  the  column  or  by  means 


of  a  gas  jet  at  the  top — the  object  being  to 
create  an  upward  draught. 

(d)  Deodorisation  of  the  sewage  and  sewer 
air  by  the  addition  of  disinfectants,  chemicals, 
&c. 

NATUEAL  VENTILATION  of  sewers  depends 
upon  the  same  laws  as  those  which  govern  the 
circulation  of  air  in  buildings,  and  is  the  system 
most  generally  relied  upon.  Movement  of  the 
air  depends  upon  the  differences  of  tempera- 
ture between  the  inside  and  outside  of  the 
sewers,  upon  the  outside  wind  currents  setting 
up  aspirating  or  extractive  effects  by  blowing 
across  the  tops  of  ventilating  columns,  man- 
holes, and  other  openings,  also  upon  the 
variations  of  flow  in  sewers  and  the  conse- 
quent displacement  of  air.  The  conditions  of 
the  atmosphere,  wind,  &c.,  largely  influence 
the  working  of  natural  systems  of  ventilation, 
hence  it  is  frequently  found  that  columns, 
unaided  by  heat  or  other  artificial  force,  are 
inoperative,  and  occasionally  observed  to  be 
passing  a  current  of  air  in  the  reverse  direc- 
tion to  that  intended.  Ventilation  shafts, 
when  sufficiently  numerous,  afford  useful 
points  of  relief  of  pressure  within  the  sewers, 
especially  in  hilly  districts  where  the  sewers 
become  rapidly  charged  and  either  force 
through  or  siphon  out  the  traps  on  house 
drainage  systems.  Street  columns  are  usually 
spaced  from  100  to  200  yards  apart  and 
especially  at  the  high  or  dead  ends  of  sewers 
where  they  give  the  best  effect.  The  shafts 
should  be  from  20  to  30  ft.  in  height,  and 
preferably  not  less  than  9  in.  in  diameter,  to 
prove  of  any  considerable  ventilating  efficiency. 
Shafts  placed  up  the  side  walls  of  houses  are 
usually  much  less  effective  owing  to  the  num- 
ber of  bends  occasioned  in  the  fixing,  and  to 
the  occasional  overshadowing  of  the  tops  of 
the  shafts  by  roofs  of  surrounding  properties. 
Every  right-angled  bend  reduces  the  venti- 
lating effect  by  about  one-fourth.  Kust  and 
dirt  also  accumulates  at  the  bends,  which  in 
time  seriously  reduces  the  efficiency  of  the 
ventilator.  The  thorough  ventilation  of  large 
mileages  of  sewers  is  a  matter  of  some  con- 
siderable difficulty,  and  whatever  system  is 


494 


YEN 


MUNICIPAL   AND    SANITARY  ENGINEERING. 


YEN 


adopted,  it  should  be  simple  and  free  from  all 
complicated  apparatus  and  independent,  as  far 
as  possible,  of  mechanical  aid.  This  simpli- 
fication is  necessary  in  order  that  the  cost  of 
installation  and  of  annual  maintenance  may 
be  confined  to  within  moderate  limits,  other- 
wise the  system  could  not  be  reasonably 
extended  over  large  areas.  The  direction  of 
sewer  air-currents  varies  with  the  position  and 
direction  of  the  lines  of  sewers  with  relation 
to  the  prevailing  winds.  In  hilly  districts  the 
sewer  gases  tend  to  accumulate  in  the  higher 
parts,  unless  checked  in  short  sections,  as  is 
sometimes  the  case,  by  means  of  ramps  or 
drop  pipes  fitted  with  flaps,  so  that  any  gases 
accumulating  in  each  section  may  be  separately 
dealt  with,  instead  of  traversing  the  whole 
length  and  rise  of  the  sewer.  The  accumu- 
lation of  sewer  gases  at  the  upper,  or  their 
fall  to  the  lower,  parts  of  a  se\verage  system 
necessarily  varies  from  time  to  time  according 
to  the  relative  specific  gravities  of  the  gases  or 
air  currents  which  obtain  at  any  given 
moment. 

HEAT  EXTRACTION  of  sewer  gases  is  a  good 
method  of  ventilation  if  employed  under 
proper  safeguards,  and  when  it  can  be  in- 
stalled without  involving  an  excessive  initial 
outlay  and  subsequent  heavy  maintenance 
costs.  The  use  of  gas-heated  ventilation 
columns  involves  a  heavy  annual  expense 
amounting,  very  usually,  to  from  £12  to  £15 
per  year,  and,  as  the  number  of  such  columns 
in  even  a  medium-sized  town  may  need  to  be 
over  a  hundred  it  will  be  seen  that  a  serious 
yearly  expense  is  entailed.  It  should  also  be 
remembered  that  accidents  occasionally  arise 
in  the  combustion  of  sewer  gases,  which  some- 
times contain  explosive  mixtures,  such,  for 
example,  as  when  a  leakage  of  coal  gas  gains 
access  to  the  sewers.  The  connection  of  sewer 
ventilation  pipes  to  tall  chimney  shafts  also 
involves  considerable  risk  of  dangerous  ex- 
plosions, and  so  is  now  seldom  adopted. 

MECHANICAL  VENTILATION  has  been  tried  in 
many  different  forms,  principally  by  the 
application  of  fans,  but  the  effect  of  these  is 
discernible  only  over  very  short  lengths  of 


sewer,  and,  moreover,  is  readily  overpowered 
and  counteracted  by  wind  currents  and  natural 
differences  of  temperature.  Heavy  initial 
outlay,  running,  and  maintenance  charges  are 
an  effectual  bar  to  the  wide  adoption  of  this 
means  of  ventilation. 

In  deep  sewers  it  is  frequently  necessary  to 
propel  air  into  the  sewer  at  one  end  and  to 
extract  vitiated  air  from  the  other  by  means 
of  large  fans  driven  by  motive  power. 

DEODORISATION  is  not  properly  speaking  a 
system  of  ventilation,  inasmuch  as  it  does  not 
remove  the  foul  and  introduce  fresh  air,  but 
simply  relies  upon  the  covering,  disinfection, 
and  deodorisation  of  offensive  gases  emanating 
from  sewage.  Care  is  required  as  to  the  kind  of 
deodorants  or  chemicals  used  as  their  employ- 
ment affects  the  final  treatment  of  the  sewage 
at  the  outfall  works.  The  cost  of  chemicals 
and  the  necessary  attention  to  their  applica- 
tion renders  the  process  too  expensive  for 
wide  application,  although  it  may  be  useful 
in  certain  special  cases. 

EXAMINATION  AND  ENTRY  OF  SEWERS. — The 
condition  of  the  air  in  sewers  requires  careful 
testing,  especially  in  the  case  of  deep  sewers, 
before  workmen  should  be  allowed  to  enter. 
This  is  most  conveniently  done  by  first  lowering 
a  lighted  candle ;  if  the  light  goes  out  or  burns 
dimly  the  sewers  should  not  be  entered  until 
thorough  ventilation  and  change  of  air  has 
been  effected,  and  the  conditions  of  the  atmos- 
phere of  the  sewer  again  tested  by  means  of  a 
light.  Should  there  be  any  sign  of  explosive 
gases,  "  safety  lamps  "  should  be  used.  In 
the  present  days  of  the  very  general  employ- 
ment of  motor-cars  and  the  consequent  ex- 
tended use  of  petrol,  it  is  found,  as  a  matter 
of  experience,  that  this  inflammable  liquid 
often  gains  access  to  the  sewers,  by  accident 
or  otherwise,  so  that  increased  care  of  entry 
and  the  use  of  covered  lights  is  essential. 

W.  H.  M. 

Venturi  Meter, — This  is  a  very  useful 
apparatus  for  the  measurement  of  large 
volumes  of  water,  such  as  are  passed  through 
a  rising  main,  leading  supply  pipe,  or  delivery 


495 


VIT 


ENCYCLOPEDIA  OF 


VIT 


pipe  from  filter  beds.  The  meter  consists  of 
two  parts,  the  tube  and  the  recording  appar- 
atus. The  tube  is  fixed  within  and  forms  a 
part  of  the  ordinary  pipe  line,  and  only  differs 
from  it  by  presenting  for  a  short  distance  a 
truncated  reducing  cone  coupled  by  a  throat- 
piece  to  a  similar  expanding  cone  (see  Figure). 
These  reducing  cones  form  the  Venturi  tube, 
and  there  are  thus  no  moving  parts  in  contact 
with  the  water.  The  measurement  is  obtained 
by  the  application  of  the  Venturi  law,  that 
water  flowing  through  a  pipe  of  diminishing 
area  loses  lateral  pressure  as  it  gains  in 
velocity.  The  difference  in  pressure  thus 
obtained  between  the  up-stream  end  of  the 
reducing  cone  and  the  "  throat  "  is  termed  the 
"  Venturi  head,"  and,  as  the  velocity  in  the 
pipe  is  proportional  to  the  square  root  of  this 
reduction  of  pressure,  the  velocity  and  thence 


Connections  with, 
^Recording  Apparatus 


Venturi  Meter. 

the  rate  at  which  the  water  is  delivered 
through  the  pipe  is  inferred  as  a  question  of 
hydrodynamics.  The  observed  reduction  of 
pressure  caused  by  the  contraction  of  the  pipe 
is  conveyed  by  two  small  tubes  (shown  in 
Figure)  to  the  recording  apparatus  which 
may  be  fixed  anywhere  within  1,000  ft.  of  the 
tube,  or,  if  so  desired,  the  registration 
may  be  conveyed  electrically  to  any  dis- 
tance. The  recorder  is  a  somewhat  com- 
plicated apparatus,  consisting  broadly  of  a 
mercurial  U  tube  receiving  and  embodying 
the  element  of  the  Venturi  head,  and  of 
appropriate  clockwork  and  gear  which  sup- 
plies the  element  of  time,  for  the  purpose 
of  automatically  recording  the  rate  of  flow 
upon  a  revolving  diagram  and  exhibiting  upon 
a  counter  the  total  quantity  of  water  passed. 


Vital  Statistics. — The  science  of  statistics 
involves  the   collection    of    individual    facts, 


with  the  view  of  grouping  them  into  different 
classes  according  to  certain  definite  characters 
they  possess.     These  dividing  characters  must 
be  constant,  and  must  be  definite.     The  uses 
of  vital  statistics  are  to   obtain   information 
as   to   the   health   of  the  people,  as   to   the 
various  diseases   from  which  they  suffer,  to 
assist  in  the  study  of  the  good  and  evil  con- 
ditions affecting  humanity,    and  to    furnish 
the  necessary  data  for  life  assurance.      For 
the  purposes  of  vital  statistics  it  is  necessary 
to  have  a  correct  enumeration  of  the  popu- 
lation   (see    "  POPULATION,    ENUMERATION  or), 
and  a  complete  and  accurate  registration  of 
births  and  deaths ;  and  when  conclusions  are 
formed  and  comparisons   made   it   must   be 
borne  in  mind  that  the  likelihood  of  accuracy 
increases  as  the  square  root  of  the  number  of 
units  dealt  with.     Annual  death-rates,  birth- 
rates, and    marriage-rates   are    gene- 
rally expressed   as   so   many   deaths, 
births,    or    marriages    among    every 
1,000  of  the  living  population;    they 
are,    therefore,    obtained    by    multi- 
plying the  number  of  births,  deaths, 
or    marriages    during    the    year,    by 
1,000,    and    then    dividing     by    the 
number   of    the   population.      If  the    period 
for    which   a   birth    or    death-rate    is   calcu- 
lated  is  less   than  a  year,  the  rate  then  in- 
dicates  the   number  of  births  or  deaths  per 
1,000    of    the    population    that    would    take 
place  in  the  year  if  the  proportion  of  births  or 
deaths  recorded  during  these  shorter  periods 
were  maintained  throughout  the  year.     Thus 
a  monthly  death-rate  would  be  calculated  by 
taking  the  deaths  registered  during  four  weeks, 
multiplying  these  by  the  thirteen  four- weekly 
periods   in   the   year,    and  then  multiplying 
by    1,000    and    dividing  by  the   number   of 
the    population.      Now   the    proportions    of 
children,  middle-aged  persons,  and  old  people 
to  the  total  population  may  vary  in  different 
communities,  and  as  the  death-rate  varies  at 
different  ages  of  life,  and  even  between  males 
and   females  at  the  same  ages,  a  correction 
must  be  made  for  any  differences  in  the  age 
and  sex  distribution  before  it  is  fair  to  com- 


496 


VIT 


MUNICIPAL   AND    SANITAEY   ENGINEERING. 


VIT 


pare  the  general  death-rates  of  two  towns. 
The  means  of  obtaining  the  factor  or  "  figure 
for  correction "  is  fully  described  in  the 
Annual  Summary  of  the  Registrar-General 
for  the  year  1883,  and  the  lengthy  procedure 
is  outlined  in  most  text-books  of  hygiene  and 
public  health.  The  multiplication  of  the 
recorded  death-rate  of  the  district  by  this 
factor  gives  the  death-rate  which  would 
obtain  in  that  district  if  the  sex  and  age  dis- 
tribution of  the  population  of  the  district 
were  in  the  same  proportion  as  it  is  in  the 
country  as  a  whole  —  thus  eliminating  the 
accidental  differences  due  to  sex  and  age,  and 
affording  a  fair  means  of  comparison  of  the 
healthiness  of  the  district.  It  is  obvious  that 
the  factor  for  correction  can  only  be  calcu- 
lated when  the  precise  age  and  sex  distribution 
of  the  population  has  been  recently  revealed 
by  a  census.  There  are  other  precautions 
which  must  be  taken  in  order  to  avoid  un- 
founded and  erroneous  statistical  deductions. 
The  number  of  deaths,  for  instance,  at  a  cer- 
tain age-period  must  be  expressed  as  the 
proportion  of  the  number  living  at  the  age 
in  question,  this  number  as  we  have  seen 
varying  considerably  in  different  communities  ; 
moreover,  a  special  disease  may  be  one 
mainly  affecting  certain  age-periods,  and  a 
like  error  will  be  involved  if  the  rate  is  not 
expressed  as  per  1,000  of  the  population 
living  at  the  same  ages,  and  of  the  same  sex, 
as  those  attacked.  Therefore  it  is  a  general 
rule  in  calculating  death-rates  that  when  the 
disease  affects  only  a  particular  section  of  the 
community  it  should  be  expressed  as  the  rate 
of  mortality  to  every  1,000  of  those  who 
are  liable  to  contract  the  disease.  A  good 
illustration  of  the  application  of  this  principle 
is  to  be  found  in  the  puerperal  fever  death- 
rate,  which  is  taken  as  the  ratio  of  the  deaths 
from  puerperal  fever  to  every  1,000  registered 
births,  since  only  those  females  who  have 
recently  been  delivered  of  a  child  are  liable 
to  die  from  this  complaint. 

Mild  winters  and  cool  summers  favour  a 
low  death-rate  from  the  lessened  mortality 
from  respiratory  diseases  and  certain 


intestinal  diseases.  The  best  statistical 
evidence  of  the  health  of  the  community  is 
furnished  by  the  corrected  death-rate,  although 
a  sick-rate,  were  it  available,  would  furnish 
still  better  evidence.  The  zymotic  death- 
rate  also  affords  valuable  evidence  of  the 
sanitary  circumstances  of  a  community.  The 
zymotic  death-rate  represents  the  proportion 
of  deaths  from  the  seven  principal  zymotic 
diseases  to  every  1,000  of  the  population. 
The  seven  zymotic  diseases  recognised  by  the 
Registrar-General  are:  —  Small-pox,  measles, 
scarlet  fever,  diphtheria,  whooping-cough, 
"fever"  (namely,  typhus,  enteric,  and  simple 
continued  fevers),  and  diarrhoea.  Of  these 
enteric  fever  and  diarrhoea  are  more  particu- 
larly associated  with  insanitary  surroundings. 
The  death-rate  from  consumption  is  also 
evidence  of  certain  insanitary  conditions  of 
housing  and  of  occupation  ;  and  the  rate  of 
infantile  mortality  also  ranks  high  as  evidence 
of  the  health  of  the  community.  With  refer- 
ence to  this  latter  rate  it  must,  be  pointed  out 
that  an  infant  is  taken  to  be  a  child  under  one 
year  of  age,  and  the  rate  is  therefore  expressed 
as  the  proportion  of  deaths  under  one  year 
of  age  to  every  1,000  registered  births. 
A  life-table  is  a  very  valuable  means  of 
comparing  the  vitality  of  a  community  at  one 
period  with  that  of  another  period  or  with 
that  of  another  community.  By  furnishing, 
by  the  law  of  probability,  the  expectation  of 
life  of  the  different  members  of  the  com- 
munity, it  supplies  a  valuable  comparative 
figure  for  statistical  purposes,  and  one  which, 
by  enabling  us  to  measure  the  probability  of 
life  and  death,  affords  a  scientific  basis  on 
which  the  calculations  for  life  assurance  are 
based.  A  life-table  represents  a  generation 
of  individuals  passing  through  life  to  extinc- 
tion ;  and  the  calculations  of  a  life-table  relate 
to  an  arbitrary  number  of  individuals  supposed 
to  be  born  simultaneously,  and  to  exist  under 
the  same  conditions  as  those  which  apply  to  a 
general  community.  Usually  the  population 
is  assumed  to  start  with  1,000,000  births,  and 
these  are  divided  into  males  and  females  in 
proportion  to  the  actual  number  of  births  of 


M.S.E. 


497 


K  K 


WAN 


ENCYCLOPEDIA   OF 


WAS 


either  sex  that  have  occurred  in  the  given  com- 
munity during  an  inter-censal  period  of  10 
years.  The  mathematical  probability  of 
survival  of  every  individual  for  each  year  of 
life  is  then  calculated  from  data  obtained  from 
the  actual  community,  and  thus  the  hypo- 
thetical life-table  population  becomes  the 
medium  for  the  record  of  facts  concerning  the 
vitality  of  a  given  population.  By  the  English 
table  for  1881 — 90  the  expectation  of  life  at 
birth,  for  males,  is  43*66  years ;  whereas 
amongst  females  the  expectation  of  life  is 
47*18.  For  the  purposes  of  comparing  occupa- 
tional mortality,  the  death-rates  amongst  those 
employed  in  different  occupations  must  be 
severally  compared  with  the  death-rate  for 
England  and  Wales  for  the  corresponding  age 
periods  and  sex.  In  that  way  "  a  comparative 
mortality  rate  "  can  be  obtained. 

THE   CHIEF  VITAL   STATISTICS   OF  ENGLAND  AND 
WALES  FOR  THE  YEAR  1907. 

The  general  death-rate  15*0*      per  1,000  per  annum. 

The  marriage-rate      .  .  15'8             ,,                 ,, 

The  birth-rate             .  .  26'3*           „                 „ 

The  phthisis  death-rate  1'14           ,,                 ,, 

The  zymotic  death-rate  T26*         ,,                 ,, 

The  scarlet  fever  death- 
rate   0-092*       „                 „ 

The  enteric  fever  death- 
rate    0-067*       „                 „ 

The  diphtheria   death- 
rate    0-164         „                 ., 

The  measles  death-rate  0-361         ,,                 ,, 

The    whooping  -  cough 

death-rate    .  .          . .  0'293         ,,                 „ 

Diarrhceal      diseases 

death-rate    .  .          . .  0-305*       „                 „ 

The  rate   of  infantile  mortality  was  118*  per  1,000 
registered  births. 

*  The  lowest  on  record. 

H.  R.  K. 

Wanklyn  &  Cooper's  System  of 
Sewage  Purification  was  proposed  in  1899, 
and  consists  of  a  system  of  aeration  with 
continuous  flow  through  a  series  of  tanks. 
The  aeration  is  aimed  at  by  the  application  of 
means  for  continually  removing  the  top  layer 
of  liquid  and  placing  that  layer  down  at  the 
bottom  of  the  next  tank  in  the  series.  The 


sewage  has  to  be  elevated  to  give  a  fall  of  7  ft., 
thus  providing  for  a  drop  of  about  4  in. 
between  each  of  the  series  of  tanks. 

Waring  System  of  Sewage  Treatment. 

— Colonel  George  Waring  obtained  permission 
in  1894  to  treat  a  portion  of  the  sewage  of 
Newport,  Rhode  Island,  and  there  conducted 
experiments  with  the  view  of  dealing  with  a 
large  volume  of  sewage  with  a  given  tank 
capacity  by  means  of  a  continuous  system  of 
working  assisted  by  forced  aeration.  The 
Waring  system  differs  from  Lowcock's  method 
(see  LOWCOCK'S  FILTERS)  principally  in  regard 
to  the  separate  treatment  of  the  sewage  sludge 
by  the  employment  of  aerators.  The  sewage 
first  passed  a  settling  chamber  for  the  removal 
of  road  grit,  thence  through  a  shallow  bed  of 
coarse  broken  stone  to  take  out  the  coarser 
solids,  and  following  this  through  "straining 
tanks  "  containing  stones  and  gravel  with  the 
object  of  effecting  a  mechanical  sedimentation. 
The  sludge  from  the  latter  when  requiring 
emptying  passed  into  a  separate  aerating  tank 
again  containing  stones  and  gravel,  where  air 
was  constantly  forced  through  the  material 
and  the  sludge  dissolved  by  bacterial  action. 
The  straining  tank  was  also  rendered  fit  for 
re-use  by  forcing  air  through.  Since  the  first 
experimental  work  there  have  been  alterations 
of  detail,  and  installations  have  been  carried 
out  at  Willow  Grove  Park,  Philadelphia,  East 
Cleveland,  Ohio,  and  many  other  places  in  the 
United  States. 

Wash-Houses,  Public. — ACTS  OF  PARLIA- 
MENT.— Power  to  erect  Public  Wash-houses  is 
contained  in  the  Baths  and  Wash-houses  Act, 
1846,  and  the  subsequent  Amendments  of 
1847  and  1882.  These  sections  also  provide 
that  the  proportion  of  second-class  washing 
accommodation  shall  be  equal  to  twice  the 
accommodation  of  the  first-class  (if  any),  and 
the  maximum  scale  of  charges  are  also  set 
forth. 

GENERAL  CONSIDERATION. — When  consider- 
ing the  question  of  a  Public  Wash-house, 
account  must  be  taken  of  the  neighbourhood, 


498 


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MUNICIPAL   AND    SANITAKY   ENGINEEEING. 


WAS 


whether  it  is  advisable  to  combine  this  pro- 
vision along  with  the  swimming  and  slipper 
baths.  Should  the  locality  where  the  swim- 
ming baths,  &c.,  are  to  be  provided  be  some- 
what of  a  superior  character  it  may  be  desir- 
able to  build  the  wash-house  separate  and 
erect  it  in  an  industrial  locality.  An  isolated 
building  will  be  much  more  expensive  to 
administer,  but  may  be  more  convenient  to  the 
users.  If  the  wash-house  is  erected  along 
with  the  whole  system  of  the  baths,  the 
entrance  should  be  set  in  a  side  or  back  street 
so  as  to  be  away  from  the  traffic  and  not 
interfere  with  the  main  entrance  to  the  swim- 
ming and  slipper  baths. 

ENTRANCES,  &c. — Immediately  inside  the 
entrance  door  there  should  be  a  way  into  a 
covered  forecourt  where  the  women  may  leave 
their  perambulators,  mailcarts,  &c.,  used  for 
carrying  their  washing,  until  they  return  home. 
Arrangements  should  then  be  made  for  the 
washers  to  pass  a  barrier  with  their  bundles, 
obtain  their  tickets  from  the  office,  and  await 
their  turn  in  a  waiting  room. 

TICKET  OFFICE. — This  should  be  so  arranged 
that  the  clerk  may  control  the  women's  second, 
(and  perhaps  the  first)  class  slipper  baths,  if 
possible,  at  the  same  time  as  the  wash-house. 
In  this  case  the  first-class  bathers  would  pass 
on  one  side  of  the  office  and  the  second-class 
and  the  women  washers  on  the  other.  This 
will  depend,  however,  on  the  amount  of  business 
done — should  the  number  of  washers  be  large 
it  may  result  in  a  ticket  office  being  required 
exclusively  for  the  wash-house. 

WAITING  EOOM. — The  waiting  room  should 
have  lockers  for  the  women,  and  a  table,  &c., 
for  partaking  of  refreshments,  as  well  as  an 
open  fireplace  where  water  may  be  boiled. 

WASHING  EOOM. — The  wrashing  compart- 
ments, which  generally  number  about  50, 
should  be  arranged  on  either  side  of  a  central 
division  with  the  supply  pipes  running  over 
the  partition.  All  iron  should  be  galvanised. 
There  should  be  three  troughs,  one  each  for 
boiling,  washing,  and  rinsing  or  blueing,  and  a 
shelf  on  top  for  soap,  &c.  The  troughs  are 
generally  of  iron,  but  occasionally  are  of 


porcelain.  In  the  former  case  they  are 
removable  for  cleansing  purposes.  If  the 
compartments  are  arranged  on  either  side  of 
a  central  division  and  the  washers  in  two 
rows  side  by  side,  each  compartment  will 
occupy  a  space  4  ft.  long  by  3  ft.  6  in.  deep. 
The  compartments  are,  however,  sometimes 
ranged  on  either  side  of  a  central  division, 
but  the  troughs  are  placed  in  pairs  at  right 
angles  to  the  partition.  This  is  a  much 
more  expensive  method,  but  it  allows  the 
drying  horse  to  be  arranged  parallel  to  the 
system,  and  permits  each  washer  to  see  her 
clothes  horse.  The  partitions  between  each 
compartment  are  about  5  ft.  high  and  are 
solid  only  down  to  within  2  ft.  of  the  ground. 
Ample  space  must  be  allowed  for  washing 
down  by  the  staff  and  the  free  use  of  a  broom. 
A  continuous  slatted  foot-board  should  be 
provided  for  the  women  to  stand  on  while 
washing.  Particular  attention  must  be  given 
to  the  question  of  drainage,  so  that  the  waste 
water  may  be  quickly  carried  off  and  any 
stoppage  readily  removed.  In  the  same 
room  and  in  close  proximity  to  the  drying 
horses  there  should  be  two  or  three  hydro 
extractors  which  answer  the  same  purpose  as 
a  wringing  machine.  Care  must  be  taken  to 
make  the  belting  safe  so  as  to  avoid  accident. 
There  should  be  a  folding  table  in  the  wash- 
house,  also  hat  and  coat  pegs  for  the  women. 
The  drying  horses  should  be  placed  at  right 
angles  to  the  troughs  so  that  each  woman 
may  be  able  to  stand  sideways  to  and  watch 
for  the  safety  of  her  clothes  when  they  are  in 
the  drying  horse.  There  should  be  at  least 
one  horse  for  every  washing  compartment, 
and,  if  possible,  one  or  two  to  spare  in  case 
of  a  breakdown.  The  horses  are  generally 
6  ft.  6  in.  long  by  6  ft.  6  in.  high  and  12  in. 
on  face,  hung  entirely  from  a  top  rail  so  as  to 
avoid  grooves  in  the  floor.  Each  horse 
should  have  four  or  five  pairs  of  clothes  rails, 
and  there  should  also  be  a  thin  sheet  iron 
plate  dividing  one  horse  from  another  as  it 
prevents  a  recently  wet  article  communicat- 
ing its  dampness  to  an  almost  dry  garment. 
It  also  prevents  theft  by  transferring  articles 


499 


KK2 


WAS 


ENCYCLOPAEDIA   OF 


WAT 


from  one  horse  to  another  when  one  of  the 
horses  is  partly  withdrawn.  The  heat  is 
conveyed  from  a  small  coil  chamber  and 
driven  forward  by  a  fan  along  a  1  ft.  6  in. 
by  9  in.  iron  duct,  having  an  outlet  hole 
over  each  compartment,  the  hole  being  auto- 
matically closed  when  the  horse  is  withdrawn. 
The  horse  has  also  a  door  at  the  back, 
corresponding  to  the  front  one,  to  close  the 
chamber  when  the  horses  are  out,  and  so 
prevent  the  hot  air  from  escaping.  There 
should  be  plenty  of  top  light  and  a  Blackman 
fan  in  the  gable  to  extract  the  steam  which 
usually  fills  the  room.  W.  C.  accommodation 
should  be  provided  immediately  out  of  the 
wash-house  room.  Adjoining  the  washing 
room  and  near  the  waiting  room  and  entrance 
there  should  be  placed  the  mangling  and 
ironing  room,  fitted  with  ironing  and  folding 
tables,  stove,  and  one  or  two  box  mangles, 
mechanically  and  continuously  worked. 
These  mangles  usually  measure  10  ft.  by 
4  ft. 

AETIFICIAL  LIGHTING. — The  artificial  light- 
ing of  the  premises  should  be  by  electricity, 
if  possible,  but  a  light  should  always  be 
placed  in  front  of  each  trough.  R.  J.  A. 

Waste-Pipes.     (See  "  PLUMBING.") 

Waste  Preventers. — Cisterns  for  flush- 
ing closets  and  other  sanitary  fittings,  arranged 
to  discharge  a  limited  quanity  of  water  at 
each  flush.  The  quantity  of  water  permitted 
to  be  used  by  the  majority  of  water  com- 
panies is  2  gallons  for  each  discharge. 
Where  no  such  restrictions  apply  a  3- 
gallon  flush  is  desirable.  Flushing  cisterns 
of  this  nature  are  generally  actuated  by  a 
chain,  which  when  pulled  either  admits  water 
to  the  long  leg  of  the  siphon  in  the  cistern  or 
forces  a  body  of  water  over  the  bend  of  the 
siphon  and  brings  about  the  discharge  of 
the  cistern.  The  details  of  construction  in 
the  working  parts  of  the  cisterns  vary  greatly, 
but  all  depend  upon  one  of  these  two 
principles ;  simplicity  of  mechanism  is  always 
an  advantage. 


Water  Analysis. — Microscopical  Examina- 
tion— Chemical  Examination — Chlorides — Hard- 
ness— Ammonia — Oxidised  Nitrogen — Nitrites — 
Poisonous  Metals — Phosphates — Organic  Matter 
— Interpretation  of  Analysis. — Water  is  usually 
analysed  to  ascertain  its  fitness  for  drinking 
and  other  domestic  purposes.  It  is  also 
examined  to  determine  its  suitability  for  use 
in  steam  boilers,  and  for  special  manufacturing 
purposes.  In  the  sanitary  analysis  of  water 
a  point  of  great  importance  frequently  lost 
sight  of  is  that  the  analyst  is,  except  in  the 
comparatively  rare  cases  where  the  water 
contains  a  poisonous  metal,  not  engaged  in 
seeking  for  the  actual  substance  that  may  do 
harm  to  the  consumer  of  the  water,  but  in 
estimating  small  quantities  of  substances  that 
are  found  by  experience  to  be  the  usual  con- 
comitants of  polluting  matter  which  may 
contain  harmful  bacteria.  Such  substances 
are  present  in  varying  amount  in  drinking 
water  from  most  sources,  and  if  an  analyst 
is  examining  a  water  for  the  first  time,  and 
without  any  knowledge  of  its  derivation  or 
surroundings  he  cannot  so  surely  certify  its 
purity  as  when  he  possesses  such  information. 

It  is  by  the  periodical  examination  of  a 
water  that  the  most  useful  information  can  be 
obtained,  as  any  influx  of  polluting  matter 
is  almost  sure  to  be  detected  by  a  careful 
microscopical,  chemical,  and  bacteriological 
examination.  Sometimes,  from  motives  of 
economy,  water  supplies,  whether  public  or 
private,  are  examined  very  seldom,  or  not  at 
all.  In  other  cases  periodical  examinations 
are  made  and  the  more  frequently  and 
minutely  this  is  done  the  sooner  any  varia- 
tion in  the  water  will  be  detected  and  the 
cause  ascertained.  It  is  highly  desirable  that 
all  waters  should  be  submitted  to  all  three 
methods  of  examination.  The  microscopical 
examination  possesses  the  advantage  of 
rapidity,  and  in  some  cases  the  actual  cause 
of  trouble  and  the  spot  where  it  takes  place 
can  be  ascertained  more  quickly  than  by  any 
other  means.  The  chemical  examination  has 
the  great  advantage  that  it  is  less  liable  to 
accidental  fluctuations  than  the  bacterial  con- 


500 


WAT 


MUNICIPAL   AND    SANITAEY   ENGINEEKING. 


WAT 


tents  of  a  water,  and  that  the  chemical  bodies 
that  accompany  or  are  generated  by  pollution 
remain  to  some  extent  in  the  water  and 
indicate  that  undesirable  matters  can  gain 
access  to  the  water,  even  if  the  bacteria 
which  accompanied  them  are  no  longer 
present.  The  chemical  data  yielded  by  a 
water  are  governed  by  the  strata  through 
which  or  over  which  the  water  flows,  whether 
the  gathering  ground  is  cultivated  or  not,  by 
the  rainfall  and  the  temperature.  Thus  water 
collected  from  chalk  or  limestone  will  contain 
carbonate  of  calcium  ;  water  from  a  ferru- 
ginous formation  may  contain  iron,  and 
waters  from  peaty  ground  vegetable  acids. 

The  bacteriological  examination  of  a  water 
has  the  advantage  of  affording  a  test  which  in 
many  cases  is  of  greater  delicacy  than 
chemical  analysis.  It  has  repeatedly  been 
shown  that  an  exceedingly  small  quantity  of 
polluting  material  (sewage  for  example)  may 
be  added  to  an  otherwise  pure  water,  which, 
though  incapable  of  detection  by  chemical 
means,  can  be  detected  with  ease  and  certainty 
by  a  bacteriological  examination.  The  fact 
that  it  is  not  often  possible  to  detect 
specific  bacteria,  such  as  the  bacillus  of 
typhoid  fever  in  an  actual  water  supply,  does 
not  detract  seriously  from  the  usefulness  of  a 
routine  bacteriological  examination,  when  we 
are  able  to  detect  variations  in  the  number  and 
character  of  the  bacterial  population,  which 
are  greater  than  can  be  accounted  for  by  any 
alterations  of  temperature  or  other  normal 
causes.  (See  also  "  WATER,  SAMPLING  OF.") 

THE  MICROSCOPICAL  EXAMINATION  OF  WATER. 
—It  is  necessary  in  the  first  place  to  draw  a 
distinction  between  waters  that  have  been 
filtered,  either  naturally  or  artificially,  and 
those  that  have  not.  For  instance,  an  upland 
water  that  has  been  artificially  filtered  through 
sand,  or  a  chalk  water  that  has  been  naturally 
filtered,  ought  both  to  be  almost  entirely  free 
from  visibly  suspended  matters,  while  an 
unfiltered  river  water  of  good  potable  charac- 
ter may  contain  a  considerable  number 
and  variety  of  organisms  and  other  sus- 
pended matters  without  any  suspicion  being 


thereby  caused.  The  various  organisms 
found  in  waters  are  usually  shown  in  text- 
books on  water  analysis.  Many  of  them  have 
no  hygienic  significance  at  all,  and  simply 
afford  evidence  that  the  water  has  been 
exposed  to  air  and  sunlight  and  are  found  in 
pure  mountain  streams — some  of  them  when 
present  in  quantity  may  produce  an  unpleasant 
smell  or  taste  in  the  water,  or  may  tend  to  act 
on  the  mains,  or  even  produce  such  prolific 
growth  as  to  diminish  their  capacity.  On  the 
other  hand,  microscopic  examination  may 
reveal  the  presence  of  starch  granules, 
undigested  muscular  fibre,  epithelial  scales, 
fibres  of  paper,  or  fibres  of  clothing.  The 
presence  of  these  would  naturally  require 
explanation,  and  would  cast  grave  suspicion 
on  the  water.  In  addition  to  the  above  the 
presence  of  such  organisms  as  the  sewage 
fungus  (Beggiatoa  alba),  rotifers,  or  paramcecia 
would  be  regarded  as  suspicious.  To  examine 
a  water  for  suspended  matter  it  is  usually 
customary  to  invert  the  bottle  containing  the 
sample  in  a  conical  medicine  glass  and  allow 
the  suspended  matter  to  settle  as  far  as 
possible  in  the  bottom  of  the  glass,  from  which 
it  is  subsequently  drawn  up  by  a  pipette  in  a 
few  drops  of  water  and  examined  on  a  slide 
under  the  microscope.  Most  of  the  objects 
likely  to  be  present  can  be  discerned  without 
staining ;  but  after  an  examination  it  is 
advisable  to  add  a  little  solution  of  iodine  in 
order  to  decide  whether  any  starch  granules 
are  present  or  not.  The  slide  or  slides  should 
be  examined  under  a  f  in.  and  also  under 
a  ^  in.  objectives.  With  the  latter  it  is 
frequently  possible  to  see  bacteria,  particularly 
the  motile  forms,  without  having  recourse 
to  staining.  Some  of  the  suspended  matters 
commonly  found  in  water  do  not  readily  settle 
to  the  bottom,  and  a  good  plan  is  to  employ 
a  method  of  filtration  such  as  that  proposed 
by  Dibdin,  or  the  original  method  of  Sedgwick 
and  Eafter,  or  its  modifications.  By  means 
such  as  these  it  is  possible  to  obtain  a  more  or 
less  accurate  idea  of  the  quantity  of  suspended 
matter  present,  as  well  as  to  ascertain  its 
character.  In  the  physical  examination  of  a 


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water,  particularly  when  periodical  examina- 
tions are  to  ba  made,  it  is  an  advantage  to 
record  its  colour.  This  can  be  conveniently 
judged  and  recorded  by  using  Lovibond's 
tintometer — an  apparatus  in  which  a  definite 
depth  of  the  water  is  examined  in  a  tube  and 
its  tint  imitated  by  comparing  it  with  slips  of 
colour-glass  of  standard  tints.  The  tinted 
glass  slips  are  numbered,  and  in  this  way  a 
definite  record  in  figures  of  the  tint  can  be 
obtained  for  future  comparison.  Since  any 
variation  in  the  composition  of  a  water  is  very 
likely  to  be  accompanied  by  a  change  of 
colour  capable  of  detection  by  this  apparatus, 
it  is  deserving  of  more  extended  use.  Such 
an  apparatus  if  regularly  employed  to  make  a 
daily  test  at  a  waterworks  would  be  a  useful 
means  of  giving  an  immediate  warning  of  a 
change  in  the  water  that  might  otherwise 
escape  notice.  Generally  speaking,  the  purest 
waters  possess  a  faint  blue  colour.  Eiver 
waters  and  upland  waters  may  have  a  greenish 
tint,  while  a  yellowish  colour  would  be  sus- 
picious, though  peaty  waters  may  have  a 
brownish  tint.  The  standard  glass  slips  of 
the  Lovibond  tintometer  are  coloured  red, 
blue,  and  yellow  and  hence  not  only  can  any 
tint  be  matched  by  the  use  of  the  various 
glasses,  but  the  degree  of  turbidity  can  also 
be  recorded.  The  smell  of  a  water  is  usually 
recorded  as  "  normal  "  or  "  abnormal."  In 
some  cases  the  growth  of  various  algae  may 
produce  a  noticeable  smell ;  but  it  is  very 
unusual  to  find  any  water  otherwise  fit  to  drink 
possessing  any  distinct  odour.  The  only 
exception  to  this  rule  is  the  case  of  some 
peaty  waters.  The  best  way  to  ascertain 
whether  a  water  has  smell  is  to  place  about 
200  c.c.  in  a  stoppered  bottle,  warm  up  to 
about  65°  C.,  shake,  and  then  remove  the 
stopper,  and  smell  immediately. 

CHEMICAL  EXAMINATION  OF  WATEK.  —  The 
general  method  of  procedure  adopted  by  most 
analysts  in  this  country  is  modified  to  suit 
individual  cases ;  but  the  ordinary  practice  is 
to  determine  the  following  items,  viz.,  the 
solid  residue  left  on  evaporation,  and  its  "  loss 
on  ignition,"  the  chlorine,  nitrates,  saline 


and  albuminoid  ammonias,  the  oxygen  con- 
suming power,  the  hardness,  temporary  and 
permanent,  and  the  presence  of  nitrites  and 
phosphates.  These  data  are  usually  sufficient 
in  the  case  of  a  potable  water.  In  the  case  of 
water  for  steam-raising,  it  is  necessary  to 
perform  a  mineral  analysis  of  the  solids 
because  on  the  amount  and  character  of 
these  will  depend  the  quantity  and  character 
of  the  "  scale "  likely  to  be  formed  in  the 
boilers.  The  total  solid  residue  is  estimated 
by  evaporating  a  known  quantity  of  water 
in  a  platinum  dish,  over  a  small  naked 
flame  to  a  low  bulk,  then  finishing  the 
evaporation  on  a  water-bath,  and  finally 
drying  till  constant  in  weight  in  an  air- 
oven  at  105°  C.  As  the  solids  absorb 
moisture  very  readily  they  must  be  dried  with 
care,  cooled  in  a  desiccator,  and  weighed 
quickly.  After  weighing,  it  is  customary  to 
ignite  the  solids  carefully  by  heating  them  in 
the  same  dish.  Very  useful  information  can 
often  be  obtained  by  the  appearance  and 
smell  of  these  solids  on  ignition.  Distinct 
odours  of  either  vegetable  or  animal  matters 
are  often  obvious,  or  a  perceptible  darkening 
owing  to  the  carbonising  of  organic  matter 
may  be  noticed.  The  ignition  should  be 
carried  to  such  a  point  that  all  organic  matter 
is  burnt  off,  but  at  a  sufficiently  low  tem- 
perature as  not  to  cause  the  volatilisation  of 
chlorides.  After  ignition  the  solids  are 
moistened  with  a  strong  solution  of  ammonium 
carbonate  and  again  very  gently  ignited.  This 
re-converts  the  calcium  carbonate  that  may 
have  been  rendered  caustic  by  the  first 
ignition  into  carbonate  again.  The  weight  of 
the  ignited  solids  subtracted  from  the  total 
solids  is  reported  as  "  loss  on  ignition."  The 
amount  of  total  solids  varies  from  a  grain  or 
two  per  gallon  in  rain-water  up  to  80  or  100 
grains  in  some  waters  which  are  fit  to  drink. 
Eiver  waters  may  contain  from  5  to  30  grains 
per  gallon ;  chalk  waters  from  20  to  40,  and 
upland  waters  from  10  to  20. 

CHLOKIDES. — A  very  low  figure  for  chlorides 
is  good  evidence  of  the  purity  of  a  water,  for 
the  reason  that  sewage  contains  urine  which 


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itself  contains  a  constant  amount  of  sodium 
chloride.     On  the  other  hand  a  water  may 
contain  several  grains  of  chlorine  per  gallon 
and    be   perfectly   free    from    pollution,   the 
chlorine  being   derived   from    the    geological 
formation.     As  might  be  expected,  wells  near 
the  sea   are  often  high  in  chlorides.     If  the 
figure  representing  chlorine  is  known  for  the 
particular  formation  from  which  a  water  under 
examination  is  derived,  then  any  increase  on 
this  would  be  highly  suspicions.     In  countries 
where  the  geological  structure  is  continuous 
over  wide  areas,  it  has  been  found  useful  to 
prepare  maps  indicating  the   distribution  of 
chlorine     (isocJilors)    and    though     in     small 
insular    countries    like    England    this    plan 
cannot  be   adopted    over   large   areas,    there 
are   districts   where   the   purest  waters   give 
a     constant     figure.       The     estimation     of 
chlorides     is     carried    out     by    titrating    a 
measured     quantity    of    the    water    with    a 
standard    solution    of    silver    nitrate,     using 
potassium  chromate  as  an  indicator.      It  is 
necessary  that  the  water  should  not  be  acid. 

THE  HARDNESS  of  a  water,  or  its  soap-destroy- 
ing power  is  due  principally  to  the  lime-salts  it 
carries  in  solution.  The  hardness  of  a  water 
is  composed  partially  of  salts  precipitated  by 
boiling  (temporary  hardness)  and  of  others 
which  are  not  so  removed  (permanent  hard- 
ness). The  temporary  hardness  is  due  to 
calcium  carbonate,  held  in  solution  by  dissolved 
carbon  dioxide,  and  is  nearly  all  removed  by 
boiling,  which  by  driving  off  the  carbon 
dioxide  causes  precipitation  of  nearly  all 
the  calcium  carbonate.  Water  derived  from 
chalk  and  limestone  naturally  contains  calcium 
carbonate,  while  in  water  from  the  green- 
sand  calcium  sulphate  predominates.  Water 
containing  calcium  carbonate  is  softened  on 
the  large  scale  by  adding  known  quantities  of 
milk  of  lime,  sufficient  to  neutralise  the  dis- 
solved carbon  dioxide.  This  produces  a 
precipitate  of  calcium  carbonate,  which  in 
many  cases  is  dried  and  sold  if  of  good  colour. 
The  precipitate  is  allowed  to  subside,  or  the 
treated  water  is  filtered  through  cloth  and 
comes  out  clear  and  brilliant.  Permanent 


hardness  is  not  affected  by  the  addition   of 
milk  of  lime,  or  may  be  slightly  increased  if 
the  lime  used  contains  any  sulphates.     There 
are  a  variety  of  patterns  of  self-acting  appara- 
tus sold  for  the  purpose  of  adding  regulated 
quantities  of  milk  of  lime  to  the  water  to  be 
softened.     The  milk  of  lime  must  not  be  in 
excess,  and  it  is  customary  to  test  the  purified 
water  with  a  solution  of  silver  nitrate,  which 
yields  a  brownish   tint  if   too  much  lime  has 
been  added.     The  hardness  of  a  water  may 
not  be  entirely  due  to  the  carbonate  or  sulphate 
of  calcium,  as  calcium  nitrate  or  magnesium 
salts  may  also  be  present.     In  the  laboratory 
the  hardness  of  a  water  is  usually  ascertained 
by  the  use  of  soap-solution.     This  is  prepared 
by   dissolving    10  grammes  of  Castile  soap  in 
methylated  spirit  and  making  up  to  1  litre. 
This  solution  is  then  standardised  against  a 
standard  solution  of  calcium  chloride  made  by 
dissolving  1  gramme  of  Iceland  spar  in  as  little 
hydrochloric   acid   as   possible   and  carefully 
evaporating    twice     to    dryness,     afterwards 
dissolving  in  distilled  water  "and  diluting  to 
1   litre.     The  soap  solution  is  either  diluted 
with  more  spirit  or  strengthened  (by  adding 
more  soap),  until  11   c.c.  of  soap  produce  a 
lather   lasting  about  2  minutes,  with  10  c.c. 
of  the  standard  calcium  solution,  when  diluted 
with  60  c.c.   of  distilled  water.     The  mode  of 
using  the  soap  solution  is  as  follows  : — 70  c.c. 
of  the  water  to  be  tested  is  placed  in  a  bottle 
capable   of  holding  about  200  c.c.  and  soap 
solution  is  run  in  from  a  burette  about  a  c.c. 
at  a  time,  with  occasional  shaking.     As  soon 
as  there  is  any  appearance  of  a  froth  forming, 
half  a  c.c.  is  added  at  a  time,  and  when  a  lather 
forms  that  lasts  about  2  minutes  the  volume 
of  soap  solution  used  is  noted,  and  1  c.c.  is 
deducted  for  the  amount  of  soap  that  would 
have  been  required  to  make  a  lather  if  there 
bad  been  no  hardness  at  all. 

AMMONIA. — In  all  natural  waters  a  certain 
amount  of  ammonia  is  found,  and  in  almost 
all  polluted  waters  the  amount  is  sufficient 
to  enable  it  to  be  estimated.  In  rain-water 
the  ammonia  is  derived  from  the  traces 
existing  in  the  atmosphere ;  in  upland  waters 


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it  is  due  also  to  the  decay  of  vegetation  or 
to  the  manuring  of  cultivated  ground,  or  to 
the  presence  of  animals.  Ammonia  exists  in 
water  in  two  conditions  which  are  known  as 
"  free  "  (or  saline)  and  "albuminoid  "  ammonia 
respectively.  These  are  both  estimated,  the 
estimations  being  performed  on  the  same 
quantity  of  water.  The  process  followed  is 
that  of  Wanklyn :  A  retort  or  flask  of  1  litre 
capacity  is  connected  to  a  condenser  and 
water  is  distilled  in  the  apparatus  until  the 
distillate  is  free  from  ammonia.  Then  into 
the  cleaned  flask  are  placed  500  c.c.  of  the 
sample,  a  few  pieces  of  ignited  pumice  to 
prevent  "  bumping,"  and  about  one-third 
gramme  of  ignited  sodium  carbonate.  The 
apparatus  being  connected,  the  distillation  is 
started  and  four  separate  lots  of  distillate,  each 
of  50  c.c.,  are  collected  in  Nessler  cylinders. 
To  each  of  these  cylinders  is  added  2  c.c.  of 
Nessler  solution,  when,  after  standing  for  a  few 
minutes,  those  containing  ammonia  show  a 
yellow  colour  the  depth  of  which  depends  on 
the  amount  present.  The  amount  of  ammonia 
present  in  each  Nessler  cylinder  is  found  by 
running  known  amounts  of  ammonium 
chloride  solution  (each  c.c.  =  O'Ol  milli- 
gramme ammonia)  into  other  cylinders,  filling 
to  the  50  c.c.  mark  with  ammonia-free  water, 
adding  2  c.c.  of  Nessler,  and,  after  waiting 
till  the  colour  has  properly  developed,  com- 
paring the  colours  with  those  obtained  as 
distillates.  When  correct  matches  have  thus 
been  made  the  total  of  c.c.  of  ammonium 
chloride  solution  used  multiplied  by  O'Ol  will 
give  the  amount  of  free  ammonia-in  milli- 
grammes in  500  c.c.  of  sample.  This,  when 
divided  by  500  and  multiplied  by  70,  will 
give  the  amount  in  grains  per  gallon.  To  the 
300  c.c.  of  water  left  in  the  distillate  flask 
40  c.c.  of  alkaline  permanganate  solution  is 
added,  and  the  distillation  continued  ;  four 
further  amounts  of  50  c.c.  each  are  collected 
which,  when  Nesslerised  andthe  tints  compared 
with  standard  ammonium  chloride  solution 
as  above  described,  will  give  the  amount  of 
albuminoid  ammonia.  Should  the  last  cylinder 
collected  show  signs  of  ammonia,  a  quantity 


of  ammonia-free  water  should  be  added  to  the 
distillation  flask,  and  the  distillation  continued 
until  all  the  albuminoid  ammonia  has  come 
over.  In  the  case  of  a  water  containing  a 
very  excessive  quantity  of  ammonia,  the  colour 
obtained  on  Nesslerisation  is  too  dense  to 
allow  of  accurate  comparison.  Such  a  water 
must  be  suitably  diluted  with  ammonia-free 
water  and  the  distillation  repeated.  It  is  not 
possible  to  lay  down  any  rules  as  to  the 
amounts  of  saline  and  albuminoid  ammonia 
which  should  not  be  exceeded  in  potable  waters, 
beyond  stating  that  most  pure  waters  contain 
but  little  of  either,  so  that  if  any  appreciable 
quantity  is  found,  more  especially  if  the 
amounts  present  exceed  what  has  previously 
been  found  in  the  same  water,  the  cause  should 
be  sought  for.  Saline  ammonia  is  sometimes 
found  in  perfectly  pure  chalk  waters  ;  albumi- 
noid ammonia  is  found  in  peaty  waters  (owing 
to  vegetation).  Where  there  are  a  number  of 
wells  sunk  in  similar  strata,  if  the  results  are 
compared,  it  will  be  found  that  any  which  are 
characterised  by  higher  figures  for  ammonia 
than  the  rest  will  be  found  to  show  other 
abnormal  figures,  and  an  examination  of  the 
surroundings  of  the  well  will  in  most  cases 
give  a  clue  to  the  cause  of  the  pollution.  Various 
causes  may  give  rise  to  the  presence  of  ammonia 
other  than  pollution.  A  water  containing 
nitrates  (as  many  pure  waters  do)  may,  on 
passing  through  a  galvanised  pipe,  have  some 
portion  of  the  nitrates  reduced  to  ammonia. 
Ammonia  has  also  been  found  in  waters 
owing  to  leakages  of  liquor  from  gas  works  ;  in 
this  case  it  is  probable  that  traces  of  sulpho- 
cyanides  would  also  be  detected. 

OXIDISED  NITROGEN. — This  exists  almost 
always  in  the  form  of  nitrates  (of  calcium  or 
sodium),  but  nitrites  are  also,  though  very 
rarely,  found.  Nitrates  are  characteristic  of 
chalk  waters,  but  are  generally  found  in  vary- 
ing amounts  in  most  waters.  Upland  waters, 
peaty  waters,  pure  lake  waters,  rain-water,  and 
pure  river  waters  contain  very  little,  while 
polluted  river  waters  and  polluted  wells  may 
contain  large  amounts.  Here  again  no  hard 
and  fast  rule  can  be  laid  down,  and  the  analyst 


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must  to  a  considerable  extent  be  guided  by 
comparisons.  If  a  shallow  well-water,  con- 
cerning the  surroundings  of  which  no 
information  can  be  obtained,  and  nothing  is 
known  as  to  the  nature  of  the  soil,  contains 
more  than  '5  of  a  grain  per  gallon  it  would  be 
regarded  as  suspicious,  and  if  the  chlorine 
figure  were  also  high  (i.e.,  above  3  grains  to 
the  gallon,  reckoned  as  chlorine)  these  figures 
would  lead  to  suspicion.  If  the  figure  for 
saline  ammonia  is  very  low,  it  would  show 
that  a  considerable  amount  of  oxidation  had 
taken  place,  which  is  more  or  less  correctly 
termed  "  past  pollution,"  while  if  it  is  also 
high,  present  or  recent  pollution  is  suggested. 
Nitrates  when  once  formed  are  not  very 
liable  to  further  alteration,  except  that  they 
may  be  withdrawn  by  the  various  organisms 
that  are  natural  to  some  waters,  or,  in  the 
case  of  surface  waters,  they  may  be  assimi- 
lated by  growing  plants.  They  therefore 
form  a  more  or  less  permanent  record  of 
pollution  in  those  cases  where  they  cannot  be 
produced  by  the  geological  conditions.  There 
are  three  or  four  methods  in  use  for  the 
estimation  of  nitrates,  the  two  most  generally 
employed  are  as  follows : — (1)  The  reduction 
of  the  nitrates  by  the  copper-couple  method, 
or  by  aluminium  foil  and  soda.  The  copper- 
couple  is  prepared  as  follows  :  take  a  piece  of 
thin  zinc  sheet  about  2  in.  by  4  in.,  clean  it 
with  hydrochloric  acid  and  immerse  it  for 
3  minutes  in  a  3  %  solution  of  copper 
sulphate.  Copper  will  be  deposited  on  the 
zinc  as  a  blackish  coating.  Wash  the  coated 
zinc  with  distilled  water,  place  it  in  a  wide- 
mouthed  bottle  holding  about  200  c.c.,  and 
rinse  it  with  the  water  to  be  tested  and  then 
fill  up  with  the  water  and  leave  in  the  dark 
for  24  hours.  At  the  end  of  this  time 
the  nitrates  (and  nitrites,  if  present)  will 
be  all  converted  into  ammonia.  When  the 
reaction  is  complete,  take  out  10  c.c.  by  a 
pippette  and,  after  diluting  with  ammonia- 
free  water,  distil  as  in  the  estimation  of  saline 
ammonia,  Nesslerising  as  previously  described. 
(2)  The  other  method  in  common  use  is 
the  phenyl-sulphate  method,  which,  though 


possibly  not  quite  so  accurate,  has  the  merit 
of  quickness.  Evaporate  70  c.c.  of  the  sample 
to  be  tested  in  a  porcelain  dish,  finishing  the 
evaporation  over  a  water-bath.  At  the  same 
time  evaporate  5  c.c.  of  a  standard  solu- 
tion of  potassium  nitrate,  made  by  dissolving 
"722  of  a  gramme  of  potassium  nitrate  in  a 
litre  of  distilled  water.  Each  c.c.  of  this 
standard  solution  will  be  equivalent  to  '0001 
gramme  of  nitrogen.  When  the  two  evapora- 
tions above-mentioned  are  complete,  2  c.c.  of 
phenyl-sulphate  is  added  to  the  dried  residue 
in  each  dish.  It  must  be  stirred  so  as  to  mix 
with  every  part  of  the  dried  residue  and  the 
dishes  should  be  warmed  (but  not  heated 
beyond  a  steam  heat)  for  3  minutes.  The 
phenyl-sulphate  is  made  by  mixing  18'5  c.c. 
of  strong  sulphuric  acid,  1*5  c.c.  of  water,  and 
3  grammes  of  phenol.  When  the  mixture  of 
phenyl-sulphate  and  residue  has  been  well 
mixed  and  warmed  it  is  diluted  with  10  or 
20  c.c.  of  distilled  water,  poured  into  a  Nessler 
cylinder,  made  distinctly  alkaline  with 
ammonia,  and  diluted  to  exactly  100  c.c.  in 
each  case.  It  will  be  found  that  the  standard, 
as  soon  as  it  has  been  made  distinctly  alkaline, 
assumes  a  clear  yellow  colour.  The  sample,  if 
nitrates  are  present,  will  also  show  a  yellowish 
tint  which  corresponds  to  the  amount  of 
nitrates  present.  If  the  liquid  is  clear,  nothing 
more  is  required  except  to  make  a  quantitative 
comparison  of  the  tint  with  that  of  the 
standard.  If  on  the  other  hand  it  is  cloudy, 
it  needs  filtering.  The  comparison  is  made  as 
follows : — Place  the  two  cylinders  side  by  side 
on  a  sheet  of  white  paper  by  the  window,  hold 
one  vertically  in  each  hand,  and  look  down 
through  the  liquids  at  the  paper.  If  the  two 
tints  are  the  same  colour,  the  sample  contains 
a  precisely  equal  amount  of  nitrates  to  the 
standard,  and  as  70  c.c.  were  taken,  the 
amount  would  in  this  case  be  '0005  gramme 
of  nitrogen  per  70  c.c.,  or  '5  grains  per  gallon. 
If  on  the  other  hand  the  tints  are  not  equal, 
pour  out  from  the  deeper  of  the  two  into  a 
graduated  (100  c.c.)  cylinder,  until  the  liquid 
left  in  the  Nessler  glass  matches  the  other. 
Then  reckon  how  many  c.c.  are  required  to  do 


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this,  by  subtracting  the  number  of  c.c.  poured 
out  from  100.  For  instance  if  the  sample 
was  the  deeper  and  the  tints  matched  after 
pouring  out  20  c.c.,  the  80  c.c.  left,  being 
equal  in  tint  to  the  standard,  the  sample 
must  contain  more  nitrogen  than  the  standard, 
the  calculation  being : 

Sample  =  —   -   X  "5  =  '62  grains 

oU 

per  gallon  of  nitrogen.  It  sometimes  (though 
very  rarely)  happens  that  an  impure  water 
will  produce  instead  of  a  pure  yellow  tint,  a 
greenish  or  brownish-yellow  ;  in  such  a  case 
this  process  cannot  be  relied  on,  as  unless  the 
tints  are  similar  in  character  it  is  impossible 
to  compare  them  with  accuracy. 

NITRITES.  —  As  mentioned  above,  nitrites 
are  very  seldom  found  in  potable  waters, 
but  as  their  presence  is  universally  regarded 
as  a  suspicious  sign,  it  is  customary  to  test 
for  them.  The  two  tests  usually  employed 
are  the  iodide  test  and  Gries's  test.  The 
iodide  test  is  performed  as  follows :  —  To 
20  c.c.  of  the  sample,  add  a  few  drops  of 
pure  sulphuric  acid,  a  crystal  of  potassium 
iodide  free  from  iodine,  and  a  few  drops  of 
chloroform.  Shake  up,  and  then  allow  the 
chloroform  globules  to  coalesce,  when  they 
will  have  a  pink  tint  if  nitrites  are  present. 
A  "  blank "  using  distilled  water  must  be 
made  and  should  show  no  pink  colour  what- 
ever. The  Gries's  test  is  performed  by  adding 
a  few  drops  of  sulphuric  acid  to  20  c.c.  of  the 
water  and  then  a  little  solution  of  metapheny- 
lene-diamine  hydrochloride.  If  nitrites  are 
present  an  orange -yellow  tint  will  appear. 
This  may  be  compared  against  a  standard 
made  from  nitrite  of  silver.  Standard  solu- 
tions cannot  be  accurately  prepared  from 
sodium  or  potassium  nitrites,  on  account  of 
the  instability  of  these  salts. 

POISONOUS  METALS.  —  The  chief  poisonous 
metal  to  be  sought  for  in  water  is  lead, 
though  it  is  customary  also  to  test  for 
copper  and  iron  and  sometimes  zinc.  Lead 
is  sometimes  found  in  water  owing  to  the  action 
of  soft  water  or  water  containing  vegetable  acid 
on  lead  pipes.  It  is  a  disputed  point  as  to 


what  quantity  of  lead  in  a  water  should  cause 
its  absolute  condemnation,  but  all  authorities 
are  agreed  that  even  very  small  quantities  are 
highly  objectionable.  As  lead  is  a  cumulative 
poison  there  should  not  be  more  than  one-fiftieth 
of  a  grain  per  gallon  in  drinking  water,  and 
it  is  believed  that  even  this  small  quantity 
may  have  prejudicial  results.  To  test  a 
drinking  water  for  lead  100  c.c.  may  be 
placed  in  a  Nessler  cylinder,  1  drop  of  acetic 
acid  added,  and  then  a  few  drops  of  a  clear, 
freshly  made  solution  of  sulphuretted  hydrogen. 
On  standing  for  a  few  minutes,  if  lead  is  present, 
a  darkening  corresponding  in  intensity  to  the 
amount  of  lead  present  will  be  seen  on  holding 
the  cylinder  above  a  sheet  of  white  paper.  A 
similar  tint  is  then  prepared  by  taking  various 
exact  amounts  of  a  dilute  standard  solution 
of  acetate  of  lead  and  treating  them  in  the 
same  way,  until  a  tint  is  obtained  which 
matches  the  sample.  As  copper  might  be 
present  (though  it  is  rarely  found)  it  is 
necessary  to  carry  out  a  confirmatory  test 
for  lead  which  may  be  done  by  placing  100  c.c. 
of  water  in  a  Nessler  glass  and  adding  two  or 
three  crystals  of  potassium  bichromate,  together 
with  a  drop  of  nitric  acid.  After  stirring 
up  and  allowing  to  stand  for  5  minutes  a 
yellowish  turbidity  will  make  its  appearance. 
This  turbidity  can  be  compared  more  or  less 
quantitatively,  but  if  a  large  quantity  of  the 
sample  water  is  available,  say  several  litres, 
it  may  be  evaporated  to  a  small  bulk  and  the 
precipitated  bichromate  of  lead  filtered  off  and 
weighed. 

PHOSPHATES. — Many  waters  may  be  tested 
for  phosphates  with  advantage.  If  they  are 
present  in  marked  quantity  they  must  be 
regarded  as  evidence  of  pollution,  more  par- 
ticularly if  they  occur  in  conjunction  with 
high  nitrates  and  high  chlorides.  On  the 
other  hand  their  absence  cannot  be  regarded 
as  any  proof  of  purity,  as  in  a  water  contain- 
ing much  calcium  carbonate  phosphates  might 
be  precipitated  and  filtered  out  by  the  strata 
from  which  the  water  is  being  derived.  In 
unpolluted  water  probably  only  traces  of 
phosphates  will  be  found,  but  in  polluted 


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waters  a  sufficient  quantity  is  often  obtainable 
from  2  litres  to  admit  of  weighing  the  pre- 
cipitate. Evaporate  2  litres  to  10  c.c.  Add 
a  few  drops  of  nitric  acid  until  faintly  acid, 
warm  to  80°  C.,  and  add  2  or  3  c.c.  of 
ammonium  molybdate  solution,  warm  and 
stir  for  5  minutes.  The  precipitate  (if  phos- 
phates are  present)  is  of  a  canary  yellow  colour. 
It  may  be  filtered  off  and  weighed.  The  weight 
multiplied  by  '0374  gives  the  amount  of  P2  05 
present  in  the  quantity  operated  on. 

OKGANIC  MATTER  IN  WATER. — In  addition  to 
the  various  suspended  solids  in  water  men- 
tioned under  the  microscopic  examination  of 
water,  there  is  always  a  certain  amount  of 
organic  matter  in  solution.  This  is  usually 
low  in  pure  water,  and  high  in  polluted 
waters.  The  organic  carbon  and  nitrogen 
were  formerly  ascertained  by  Frankland's 
combustion  process.  This  is  but  seldom 
performed  nowadays,  as  the  estimation  of 
the  free  and  albuminoid  ammonias  allow  an 
arrival  at  the  same  conclusion  in  a  more 
expeditious  fashion.  Organic  matter  (whether 
nitrogenous  or  otherwise)  is  determined  by 
one  or  other  of  the  "Moist  Combustion  "  pro- 
cesses. The  method  in  general  use  in  this 
country  consists  in  treating  the  water  to  be 
tested  with  an  acid  solution  of  potassium 
permanganate.  The  organic  matter  in  solution 
which  is  present  in  a  suitable  state  absorbs 
oxygen  from  the  permanganate,  and  the  excess 
of  permanganate  not  used  in  oxidation  is  esti- 
mated by  titration  at  the  end  of  a  stated  time. 
The  process,  originally  due  to  Forchammer, 
has  been  modified  in  various  ways,  so  that 
figures  by  different  observers  should  not  be 
expected  to  compare,  unless  they  employ  the 
same  details  of  procedure.  Different  workers 
also  perform  their  moist  combustion  tests  at 
different  temperatures,  causing  a  divergence 
of  results.  The  consequence  is  that  the  figure 
is  often  of  no  significance  to  any  one  besides 
the  analyst.  In  some  waters  much  of  the 
organic  matter  present  is  in  an  insoluble  con- 
dition, and  therefore  has  but  little  action  on 
the  permanganate.  The  following  method 
is  one  that  is  frequently  employed  : — Place 


250  c.c.  of  the  sample  of  water  in  an  absolutely 
clean  500  c.c.  flask  and  a  similar  quantity  of 
distilled  water  free  from  oxidisable  matter  in 
another  flask.  Warm  both  flasks  on  a  water- 
bath  to  80°  F.,  add  to  both  10  c.c.  of  standard 
permanganate  solution  (each  c.c.  of  which 
contains  0*1  milligramme  of  available  oxygen), 
and  10  c.c.  of  25  %  sulphuric  acid.  Keep  the 
flasks  warmed  to  80°  F.  If  the  colour  becomes 
sensibly  paler  in  the  sample,  add  10  c.c.  more 
of  the  permanganate  solution  to  both  flasks. 
At  the  end  of  15  minutes  (or  4  hours)  cool 
both  flasks,  and  add  to  each  one  or  two 
crystals  of  potassium  iodide.  The  pink  colour 
will  turn  to  a  yellow,  due  to  the  liberation  of 
iodine  by  the  reaction  of  the  permanganate 
with  the  iodide.  The  liberated  iodine  dissolves 
in  the  excess  of  potassium  iodide.  The  con- 
tents of  each  flask  are  then  titrated  with  a 
standard  solution  of  sodium  hyposulphite, 
finishing  the  titration  in  presence  of  a  few 
drops  of  starch  solution.  The  standard 
solution  of  permanganate  employed  contains 
"395  grammes  of  potassium  permanganate 
in  a  litre  of  water;  the  'hyposulphite  '  solution 
should  contain  about  1  gramme  to  the  litre ; 
and  the  special  sulphuric  acid  is  made  by 
adding  1  volume  of  acid  to  3  of  water  and 
then  adding  small  quantities  of  permanganate 
solution  until  a  very  faint  pink  colour  remains. 
Specimen  calculations  of  this  method  and  the 
others  mentioned  in  these  articles  will  be 
found  in  "  The  Chemical  and  Biological 
Examination  of  Water  "  (Pearmain  &  Moor). 
INTERPRETATION  OF  THE  RESULTS  YIELDED  BY 
ANALYSIS.  —  The  general  conclusions  to  be 
drawn  from  the  various  methods  that  are 
employed  in  water  analysis  have  been  dealt 
with  under  each  individual  process.  It  remains 
only  to  add  that  it  is  impossible  to  generalise 
to  the  extent  of  laying  down  hard  and  fast 
figures  for  the  purpose  of  designating  "  pure 
or  impure  "  waters.  All  the  different  features 
must  be  considered,  and  while  it  is  often 
possible  to  class  one  water  as  pure  and 
another  as  certainly  polluted,  there  remain  a 
considerable  proportion  which  must  be  regarded 
as  falling  into  an  intermediate  class,  namely, 


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doubtful,  or  only  to  be  used  with  caution.     In     continues  the  content  of  bacteria  in  the  rain 


some  cases  a  doubtful  water  is  the  only  avail- 
able one,  and  as  it  is  quite  useless  to  prescribe 
boiling  because  it  will  not  be  effectively  or 
continuously  carried  out,  the  only  alternative 
is  to  provide  efficient  filter  beds  for  large 
supplies,  and  an  efficient  filter  as  well  in  the 
consumers'  houses  (see  "DOMESTIC  FILTERS"). 

C.  G.  M. 

Water,  Bacteriology  of. — Origin  of  Bacteria 
in  Water  and  Influences  Affecting  them — Bacterial 
Indicators  of  Pollution — Enumeration  of  Bacteria 
— Detection  and  Estimation  of  B.  Coli  Communis 
—The    Streptococci — B.   Welchii — The   Typhoid 
Bacillus — The  Comma  Bacillus — The  Preparation 
of  Media. — The  nature  and  number  of  bacteria 
in  water  vary  enormously.     From  a  sanitary 
standpoint  the  actual  number  of  organisms  is 
secondary  in  importance  to  their  origin.  While 
some  bacteria  may  be  regarded  as  natural  to 
water,  others  are  washed  in  from  the  soil,  and 
in   a   sewage   polluted    water    organisms    of 
excretal  origin  will  be  found.     Provided  the 
soil  be  unpolluted  the  bacteria  derived  from 
it  do  not  affect  the  purity  of  a  water.    Should, 
however,  the  soil  be  contaminated  with  excre- 
ment, the   purification   of    water    percolating 
through   it   is   materially  dependent  on  two 
factors.     The    bacteria  natural   to   soil  have 
a   strong   antagonism    for    foreign    bacteria, 
with  the  result  that  organisms  of  facal  origin 
more   or  less   rapidly  disappear,  which    dis- 
appearance is   hastened  by  the  temperature 
and   medium   not   being   conducive    to  their 
multiplication.     In  the  absence  of  fissures  the 
soil  has  a  pronounced  filtering  property  which 
precludes   the   passage   of    bacteria   through 
more   than  a  certain  thickness.     The  depth 
necessary  to  prevent  pollution  varies  with  the 
nature  of  the   soil,   the   amount  of  polluted 
matter,  the  rate  of  flow  of  water,  and  the  exist- 
ence of  defects  allowing  freer  passage  of  water. 
The   variation  in  the   number  of  organisms 
present  in  a  water  is  governed  by  conditions 
which  operate  by  either  increasing  or  decreas- 
ing  them.    During  a  shower  the  rain-drops 
carry  down  the  aerial  bacteria ;  as  the  shower 


diminishes.      This  number   of   organisms   is 
generally  small,  and  pollution  from  this  source 
can  be  regarded  as  immaterial.     After  a  heavy 
rain,  however,  the  bacteria  in  bodies  of  water 
may    be     decreased    owing    to    dilution,    or 
increased   through    the    washing    in    of   soil 
organisms.      The   lowering   of   the   plane   of 
saturation  by  excessive  pumping  from  a  well, 
through  draining  a  larger  area,  may  bring  a 
polluted  soil  within  the  drainage  area.     An 
open  well  will  cceteris  paribus    contain  more 
organisms  than  a  closed  one  (Savage).     When 
flowing  at  a  slow  rate,  or  when  stationary,  the 
mineral  and  vegetable  particles  to  which  some 
of  the   organisms   adhere    subside,    and   the 
bacteria    may    also    congregate    together   to 
form  zoogloaa,  in  which  case  they  will  settle 
more  rapidly  than  when  isolated.    This  "  sedi- 
mentation "  constitutes  the    most  important 
factor  in  the  self-purification  of  water.    In  the 
clarification  of  water  with  alum,  &c.,  and  in 
softening  by  the  addition  of  lime  water,   as 
in  Clark's  process,  bacteria  are  mechanically 
carried  down. 

BACTEEIAL  INDICATORS  OF  POLLUTION. — The 
pollution  of  water  with  sewage  naturally 
increases  the  content  of  bacteria,  and  a  large 
number  of  organisms  would  appear  suspicious. 
This  presumption  is  strengthened  if  a  large 
proportion  of  the  bacteria  will  grow  at  blood 
heat,  and  if  the  count  on  gelatine  (grown  at 
18°  to  22°  C.)  contains  an  excessive  proportion 
of  organisms  liquefying  gelatine.  Some  of  the 
bacteria  found  in  pure  waters,  however,  liquefy 
gelatine,  others  grow  at  blood  heat,  while  the 
mere  enumeration  of  organisms  often  does  not 
give  positive  evidence  of  the  purity.  It  is,  there- 
fore, necessary  to  search  for  certain  bacteria 
which  are  normal  to  fffices,  and  which,  for  a 
time  at  any  rate,  are  capable  of  leading  a 
saprophytic  existence  in  water.  Should  these 
be  found  in  appreciable  numbers  a  conclusion 
is  generally  justified  that  the  water  is  unfit  for 
use.  The  organisms  generally  sought  for  are 
the  Bacillus  coli  communis,  streptococci  and 
Bacillus  Welchii  (Bacillus  enteritidissporn//*  nt  *}. 
These  exist  in  large  numbers  in  human  faeces, 


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but  they,  or  organisms  possessing  very  similar 
characters  which  do  not  admit  of  ready  diffe- 
rentiation, are  also  found  in  the  excreta  of 
animals  and  birds,  and  thus  do  not  necessarily 
indicate  alvine  pollution  of  human  origin. 
Pollution  with  animal  matter  of  any  kind, 
however,  seriously  discounts  the  suitability  of 
a  water  for  drinking  purposes. 

BACTEKIOLOGICAL  EXAMINATION  OF  WATER. — 
A  committee  of  the  Royal  Institute  of  Public 
Health  formulated  a  scheme  for  the  bacterio- 
logical examination  of  water  to  which  English 
workers  generally  adhere.  The  committee 
give  as  the  minimal  number  of  procedures  : 
(a)  Enumeration  of  the  bacteria  present  on 
a  medium  incubated  at  room  temperature 
(18°  to  22°  C.) ;  (b)  Search  for  Bacillus  coli 
and  identification  and  enumeration  of  the 
organism  if  present.  In  addition  the  majority 
of  the  committee  recommend  :  (c)  Enumera- 
tion of  the  bacteria  present  on  a  medium 
incubated  at  blood  heat  (36°  to  38°  C.) ; 
(d)  Search  for  and  enumeration  of  streptococci. 
As  a  routine  procedure  the  search  for  B.  Welchii 
is  considered  unnecessary.  Unless  the  neces- 
sary inoculations  into  media  can  be  made 
within  3  hours  of  collection,  the  sample 
must  be  packed  in  ice,  but  even  then  the 
examination  should  be  commenced  as  soon  as 
possible,  as  even  ice  packing  does  not  prevent 
an  alteration  in  the  bacterial  character  of 
a  water.  The  recommendations  of  the  Royal 
Institute  of  Public  Health  committee  are 
mainly  followed  in  the  following  analytical 
scheme,  and  the  composition  of  the  media 
used  are  given  at  the  end. 

ENUMERATION. — For  organisms  developing 
at  room  temperature  nutrient  gelatine  or  dis- 
tilled water  gelatine  may  be  used.  With  a 
polluted  water  the  former  allows  more 
organisms  to  grow  than  the  latter,  while 
with  a  pure  water  a  larger  count  is  generally 
obtained  with  distilled  water  gelatine.  The 
use  of  both  media,  therefore,  affords  useful 
information  ;  but  when  only  one  gelatine  is 
used  the  "  nutrient "  form  should  be  employed. 
With  a  pure  water  the  number  of  organisms 
developing  on  gelatine  is  generally  more  than 


ten  times  the  number  of   those  growing  on 
agar  at  blood  heat.     In  the  case  of  a  polluted 
water  this  ratio  of  organisms  developing  on 
gelatine   to    those  developing   on   agar   may 
become  10 :  2,  or  even  less.     With  a  polluted 
water    the    colonies    liquefying   gelatine  may 
increase  to  more    than   one-tenth    the    total 
number    on    gelatine.       For    the   counts  on 
gelatine  three  tubes  of  nutrient  gelatine  are 
melted  in  a  water  bath  at  40°  C.     Then  three 
sterile  Petri  dishes  are  inoculated  respectively 
with  0'5    c.c.,    0*3    c.c.,   and    0'2    c.c.   of   the 
sample  run  in  from  a  sterile  graduated  pipette. 
The    tubes   of    gelatine  are   taken  from   the 
water  bath  one  by  one,   the  plugs   removed, 
the  mouths  singed  in  a  Bunsen  flame,  and 
poured  one  into  each  dish.       By  tilting  the 
Petri  dishes  several  times  the  water  is  mixed 
with  the  liquefied  gelatine.     The  Petri  dishes 
are  placed  on  a  flat  surface  to  solidify,   and 
then  incubated  at  from  18°  to  22°  C.     The 
number  of  organisms  on  the  gelatine  plates  is 
counted  with  the  naked   eye    at  the    end  of 
72  hours,  any  doubtful  colony  being  deter- 
mined with  the  aid  of   a  lens.     It  is,  how- 
ever, necessary  to  inspect  the  plates  daily,  as 
sometimes  the  number  of  liquefying  colonies 
renders    an    earlier   count    necessary.       The 
counting  is  best  done  against  a  black  back- 
ground, and    when   the   colonies  on   a  plate 
are  very  numerous  a  Pakes's  disc  may  be  used 
to  lessen  the  labour  of  counting.     The  total 
number   on    the  three   plates  will    give    the 
number   in  1   c.c.     For   the  enumeration    of 
organisms  growing  at  blood  heat,  two  tubes  of 
agar  are  melted  in  a  water  bath  at  100°  C., 
cooled  to  40°  or  45°  C.,  and  the  contents  run, 
with  the  usual  precautions,  into  separate  sterile 
Petri  dishes  containing  TO  and  O'l  c.c.  of  the 
sample.     Expedition  is  necessary,  or  the  pre- 
paration will  go  "  lumpy."     The  plates  are  put 
in    the   blood-heat    incubator     and    counted 
at  the  end  of    40  to    48   hours.      For    con- 
taminated waters  it  may  be  necessary  to  dilute 
the  water  ten  or  one-hundredfold  in  order  to 
render    the    individual    colonies    sufficiently 
discrete  to  be  counted.      All    the    foregoing 
experiments   should    be    done    in    duplicate. 


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The  organisms  developing  aerobically  on 
gelatine  at  room  temperature  may  be  as 
few  as  five  or  ten  per  c.c.  in  a  water  from 
a  deep  well  or  spring,  and  do  not  usually 
exceed  100  to  150  in  a  good  water.  A 
count  of  500  per  c.c.  is  sometimes  obtained 
in  surface  waters  free  from  pollution,  but 
anything  over  this  should  raise  suspicions. 
A  thousand  organisms  per  c.c.  will  generally 
condemn  a  sample. 

DETECTION  AND  ESTIMATION  OF  BACILLUS 
COLI  COMMUNIS. — Two  single-strength  tubes  of 
MacConkey's  medium,  preferably  made  with 
lactose  instead  of  glucose,  are  inoculated  with 
O'l  c.c.  and  I'O  c.c.  of  the  water.  One 
double -strength  tube  is  inoculated  with  10  c.c. 
of  the  water,  and  two  (in  the  case  of  a  deep 
well  water,  five)  other  double-strength  tubes 
with  quantities  of  20  c.c.  each.  (The  tubes 
for  the  reception  of  the  quantities  of  20 
c.c.'s  should  contain  20  c.c.  of  the  double 
strength  medium,  so  that  it  is  not  diluted  with 
more  than  its  own  bulk  of  water.)  The  tubes 
are  incubated  at  37°  C.  (or  better  at  42°  C.) 
for  2  days.  The  reddening  of  the  medium 
showing  the  production  of  acid  and  the  col- 
lection of  gas  in  the  inner  tube  afford  pre- 
sumptive evidence  of  B.  coli.  Other  organisms, 
chiefly  of  alvine  origin,  however,  ferment 
MacConkey's  medium  with  the  production  of 
acid  and  gas,  and  it  is,  therefore,  necessary  to 
isolate  and  identify  the  colon  bacillus.  For 
this  purpose  the  tube  containing  the  smallest 
quantity  of  the  sample  which  shows  the 
reaction  is  used  to  inoculate  solid  media  for 
the  isolation  of  individual  organisms.  To 
effect  this  isolation  two  good  loopfuls  of  the 
reddened  MacConkey  medium  are  inoculated 
into  a  suitable  quantity  of  sterile  water  for 
dilution,  and  some  of  this  is  smeared  over  the 
surface  of  several  sloped  gelatine  tubes.  Or 
the  suspected  medium  may  be  smeared  over 
plates  of  Conradi-Drigalski  agar.  After 
pouring  the  Conradi-Drigalsk  agari  into  the 
sterile  Petri  dishes,  these  should  be  placed  in 
the  blood-heat  incubator,  with  the  lids  tilted 
to  allow  escape  of  moisture,  for  2  hours. 
This  partial  drying  is  necessary  to  prevent 


colonies  running  together.  (These  can  be 
incubated  at  blood  heat,  and  thus  save  time.) 
Any  colon  bacilli  will  appear  as  large  red 
colonies.  Several  suspicious  colonies  are 
inoculated  into  separate  broth  tubes,  incu- 
bated for  12  to  24  hours  at  blood  heat, 
and  then  examined  in  the  fresh  condition  to 
ascertain  motility,  while  a  cover-glass  prepara- 
tion of  the  broth  is  made  and  stained  by 
Gram's  method.1  B.  coli  is  Gram-negative, 
and  feebly  motile.  Occasionally  the  motility 
is  not  apparent.  Its  presence  is,  however,  a 
guide  as  to  the  best  tube  to  select  for  further 
work.  Subsequent  procedure  depends  on  what 
attributes  are  regarded  as  typical  of  the  colon 
bacillus.  Houston  considers  that  the  term 
should  only  be  applied  to  "  flaginac  "  organ- 
isms, i.e.,  those  producing  fluorescence  in 
neutral  red  glucose-peptone  water,  acid  and 
gas  in  MacConkey's  glucose  medium,  indole 
in  peptone  water,  and  acid  and  curd  in  milk. 
The  Eoyal  Institute  of  Public  Health  com- 
mittee give  the  following  as  characteristic 
of  typical  B.  coli:  A  small,  motile,  non- 
sporing  bacillus,  growing  at  37°  C.,  as  well  as 
at  room  temperature,  which  is  decolourised  by 
Gram's  method,  does  not  liquefy  gelatine,  and 
in  a  gelatine  stab  grows  well  to  the  bottom 
of  the  stab  (facultative  anaerobe).  It  pro- 
duces permanent  acidity  in  milk,  curdling 
the  same  within  7  days  at  blood  heat, 
ferments  glucose  and  lactose  with  production 
of  both  acid  and  gas.  It  is  also  desirable 
to  show  the  production  of  indole,  the  change 

1  GRAM'S  METHOD. — Some  of  the  culture  is  smeared 
over  a  cover-glass,  dried,  fixed,  and  stained  with 
anilin  gentian  violet  solution  (saturated  alcoholic 
solution  of  gentian  violet,  30  c.c.  ;  anilin  water, 
100  c.c.)  for  5  minutes  ;  then  immersed  in  iodine 
solution  (iodine,  1  part ;  potassium  iodide,  2  parts ; 
distilled  water,  300  parts)  for  one  half  to  2  minutes, 
when  the  film  should  have  the  colour  of  a  used  tea- 
leaf.  The  cover-glass  is  removed  from  the  iodine 
solution,  drained,  and  immersed  in  methylated  spirit 
until  the  gentian  violet  colour  no  longer  comes  aw;iy 
from  the  preparation.  The  preparation  may  be 
washed  and  counter-stained  with  eosin,  or  after  wash- 
ing it  may  be  dried,  mounted,  and  examined  straight 
away.  (N.B. — Anilin  gentian  violet  solution  does  not 
keep  for  long.) 


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in  Griibler's  neutral  red,  and  the  yellowish 
brown  growth  on  potato.  Both  Savage  and 
Hewlett  agree  in  the  main  with  these 
characters.  Therefore  the  pure  culture  in 
a  broth  tube  which  is  Gram-negative  and 
feebly  motile  should  be  inoculated  into  the 
following  media  :  (a)  gelatine,  both  in  stab 
and  surface  cultures ;  this  can  conveniently 
be  done  in  the  same  tube.  A  pearly  white 
growth  appears  along  the  streak,  which  does 
not  liquefy  the  gelatine.  This  tube  should  be 
observed  for  10  days  to  exclude  a  liquefying 
organism.  If  a  gelatine  shake  culture  be  also 
made,  bubbles  of  gas  will  be  produced  in  the 
medium.  Gas  bubbles  may  also  be  observed 
along  the  stab  in  the  stab  culture,  (b)  Litmus 
milk  incubated  at  blood  heat  will  be  reddened 
and  curdled,  (c)  Neutral  red  glucose  peptone 
water — a  yellow  colour  with  green  fluorescence 
— is  produced,  (d)  Peptone  water.  Indole  is 
produced  in  2  days.1  (e)  Various  sugar 
media,  especially  lactose  and  glucose  media, 
both  of  which  are  fermented  with  production 
of  acid  and  gas. 

Organisms  differing  from  the  typical  colon 
bacillus  in  one  or  more  respects  are  fre- 
quently met  with,  which  are  known  as 
"  atypical."  The  precise  significance  to  be 
attached  to  them  is  uncertain;  but  at  the 
same  time  the  probability  that  they  were 
originally  derived  from  excreta  must  not  be 
overlooked.  Savage  is  of  opinion  that  "the 
nearer  these  glucose  fermenting  coli-like  bacilli 
approach  typical  B.  coli  in  their  characters, 
the  more  nearly  are  our  numerical  standards 
for  that  organism  applicable  to  them,  while 
if  they  lack  essential  characters  a  propor- 

1  The  Indole  Reaction  is  obtained  by  adding  to 
10  c.c.  of  the  peptone  water  culture  of  the  organism 
1  c.c.  of  aO'l  %  solution  of  sodium  nitrite,  and  then 
allowing  a  few  drops  of  concentrated  sulphuric  acid 
to  trickle  slowly  down  the  side  of  the  test  tube.  It  is 
placed  in  the  incubator  for  half  an  hour  to  render 
the  pink  or  deep  red  colour  more  plain.  A  blank 
should  be  performed  and  the  suitability  of  the 
peptone  for  the  purpose  proved.  (N.B. — The  cholera 
spirillum  produces  a  nitrite  in  the  culture  medium 
and  gives  the  reaction  on  the  addition  of  acid 
alone.) 

511 


tionately  greater  number  must  be  present  to 
justify  an  adverse  opinion." 

Should  typical  B.  coli  be  isolated  in  this 
way,  it  was  obviously  present  in  the  amount 
of  water  inoculated  into  the  original 
MacConkey  tube  from  which  the  subcultures 
were  made,  and  is  duly  reported  as  present  in 
this  quantity.  This  particular  datum  is  by 
far  the  most  important  of  the  whole  of  the 
ordinary  examination ;  but,  like  the  other 
data,  requires  a  very  wide  and  comprehensive 
experience  for  its  correct  interpretation. 
Several  "  working  standards  "  have  been  pro- 
posed for  B.  coli.  Savage  considers  that  its 
presence  in  100  c.c.,  or  less,  of  deep  well  or 
spring  water,  or  in  10  c.c.,  or  less,  of  shallow 
well  water  justifies  an  attitude  of  great  sus- 
picion. Pakes  suggests  the  condemnation  of 
water  containing  the  organism  in  20  c.c.,  or 
less.  In  upland  surface  waters  the  signifi- 
cance of  the  colon  bacillus  is  less  certain 
owing  to  the  probability  of  its  derivation 
from  the  excreta  of  grazing  animals,  and 
Savage  is  of  opinion  that  its  presence  in  even 
2  or  1  c.c.  "  means  contamination,  but  not 
necessarily  a  contamination  which  it  is 
essential  to  prevent." 

STREPTOCOCCI. — Proof  of  the  presence  of 
these  organisms  affords  a  valuable  confirma- 
tion of  other  results  pointing  to  pollution, 
but  less  significance  can  be  attached  to  their 
absence.  The  medium  used  in  the  prelimi- 
nary detection  of  coli  (MacConkey's  lactose 
bile-salt  medium)  favours  the  growth  of 
streptococci,  and  they  should  be  looked  for  in 
hanging  drops.  Our  knowledge  of  the  subject 
does  not  at  present  allow  any  decided  opinion 
on  the  significance  of  different  species  of 
streptococci,  and  they  are  only  looked  for  as  a 
class.  It  is  uncertain  whether  they  are 
capable  of  a  saprophytic  existence  for  longer 
or  shorter  periods  than  B.  coli.  Savage, 
after  referring  to  the  inapplicability  of  arbi- 
trary standards  to  streptococci,  suggests  that 
similar  standards  to  those  he  has  advocated  for 
B.  coli  may  be  provisionally  used. 

BACILLUS  WELCHII  (this  name  is  applied  by 
Chester  to  the  organism  or  class  of  organisms 


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originally  described  by  Welch  and  Nuttall, 
which  Hewlett  believes  to  be  identical  with 
the  B.  enteritidis  sporogenes  of  Klein). — This 
organism  is  regarded  as  of  less  importance  as 
an  index  of  pollution  than  formerly,  though 
Thresh  attaches  considerable  importance  to  it. 
It  has  to  be  sought  for  in  large  quantities  of 
water,  the  usual  method  being  to  pass  500  c.c. 
of  the  sample  through  a  Pasteur-Chamberland 
candle,  suspend  the  deposit  in  5  c.c.  of  sterile 
water,  and  inoculate  three  milk  tubes  with 
3  c.c.,  1  c.c.,  and  1  c.c.  of  this  concentrated 
water  respectively.  Hewlett's  method  of  con- 
ducting the  test,  though  cumbersome,  is  much 
more  satisfactory :  Ten  large  boiling  tubes, 
each  containing  50  c.c.  of  sterile  milk,  are 
inoculated  with  equal  amounts  of  the  water  ; 
melted  vaseline  is  poured  on  the  surface  of  the 
milk  to  exclude  the  air,  and  the  tubes  heated 
to  80°  C.  for  15  minutes.  After  2  clays' 
incubation  at  blood  heat,  B.  Welcldi  produces 
a  clear  whey  and  a  honeycombed  mass  of 
casein,  while  the  gas  produced  is  shown  by 
a  bubble  under  the  vaseline  plug.  The 
B.  butyricus,  which  is  regarded  by  some  as  a 
non-pathogenic  form  of  B.  Welciiii,  gives  a 
similar  reaction,  and  the  only  satisfactory 
means  of  differentiation  is  to  inject  2  c.c.  of 
the  whey  subcutaneously  into  a  guinea-pig  of 
about  200  grammes  weight,  when  B.  Welcldi 
will  kill  the  animal  in  48  hours. 

THE  DETECTION  OF  THE  TYPHOID  BACILLUS. 
—This  organism  is  seldom  looked  for  except 
when  an  epidemic  is  in  progress.  Allow- 
ing 10  or  12  days  as  the  incubation  period, 
and  a  few  subsequent  days  for  the  prob- 
ability of  an  epidemic  to  be  appreciated, 
a  sufficient  time  may  have  elapsed  before 
the  water  is  suspected  to  allow  the  organ- 
ism time  to  die  out.  This,  coupled  with  the 
difficulty  of  its  detection  in  water,  accounts 
for  the  extreme  rarity  with  which  it  is  found 
in  water.  A  large  number  of  methods  for 
the  detection  have  been  proposed,  to  which 
want  of  space  prevents  reference.  One  which 
is  regarded  as  the  most  satisfactory,  and  has 
been  used  with  success  by  the  author,  is  given  : 
H.  S.  Willsons  Method.  —  Sufficiency  of  a 


10  %  solution  of  alum  is  added  to  the  water 
to  give  0'5  gramme  of  alum  to  the  litre. 
A  precipitate  of  aluminium  hydrate  is  formed 
which  entangles  the  bacillus.  The  vessel  is 
shaken,  and  the  water  centrifugalised.  The 
deposit  is  rubbed  up  with  a  little  of  the  water, 
and  plated  out  on  Coiiradi-Drigalski,  or 
malachite  green  agar.  On  Conradi-Drigalski 
agar  the  typhoid  bacillus  comes  up  in  small, 
clear,  blue,  dewdrop-like  colonies.  All  sus- 
picious colonies  should  be  worked  out.  The 
typhoid  bacillus  is  actively  motile,  does  not 
stain  by  Gram,  ferments  glucose  producing 
little  acid  but  no  gas,  has  little  or  no  effect  on 
lactose  or  saccharose,  produces  a  little  acid  in 
litmus  milk  but  no  coagulation  ;  except  in  rare 
instances  it  produces  no  indole ;  on  potato  it 
gives  a  moist,  shining,  grey  growth  that  is 
almost  invisible,  except  when  the  potato  has 
an  alkaline  reaction,  when  the  growth  may  be 
yellowish.  The  flagella  should  be  stained,  and 
the  agglutination  with  typhoid  serum  ascer- 
tained. Although  neither  B.  alkaligenes  nor 
B.  sulcatus  (the  two  organisms  most  likely  to 
be  mistaken  for  the  typhoid  bacillus)  aggluti- 
nate with  typhoid  serum,  some  varieties  of  the 
colon  bacillus  do. 

THE  ISOLATION  OF  THE  CHOLERA  SPIRILLUM. 
—This  organism  is  with  difficulty  detected 
in  water.  Moor  and  Hewlett  ("  Applied 
Bacteriology ")  recommend  the  addition  to 
several  hundred  c.c.  of  the  water  of  1  %  pep- 
tone and  1  %  salt,  making  faintly  alkaline 
with  sodium  carbonate,  placing  in  Erlen- 
meyer  flasks,  having  a  layer  not  more  than 
an  inch  deep  in  each  flask,  and  after 
loosely  capping  the  flasks  with  filter  paper, 
incubating  at  37°  C.  Hanging  drop  prepara- 
tions are  made  at  intervals  of  10,  15,  and 
20  hours  respectively  from  the  top  of  the 
liquid,  and  examined  for  the  organism.  Agar 
plates  are  prepared  and  incubated  at  blood 
heat,  and  any  suspicious  colonies  are  sub- 
cultured  and  examined  for  indole  produc- 
tion, &c.  A  peritoneal  inoculation  into  a 
guinea-pig  is  recommended. 

It  should  be  pointed  out  that  a  bacterio- 
logical examination  of  water  should  never  be 


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attempted  without  a  good  previous  knowledge 
of  the  principles  of  bacteriological  technique, 
and  an  appreciation  of  the  very  many  ways  in 
which  errors  may  arise.  In  inexperienced 
hands  the  experiments  may  be  absolutely 
misleading. 

PREPARATION  OF  MEDIA. — The  broth,  gela- 
tine, and  agar  media  are  made  to  a  reaction 
of  +  10  (Eyre's  scale).  That  is  to  say,  after 
the  media  have  been  prepared  they  are  made 
neutral  to  phenolphthalein,  and  then  to  every 
litre  10  c.c.  of  normal  acid  are  added.  This 
"  standardisation"  is  a  matter  of  importance, 
particularly  in  the  enumeration  of  organisms, 
as  different  counts  result  from  using  media 
of  different  reactions.  As  the  reaction  changes 
on  keeping,  the  media  should  be  used  within 
a  month  of  preparation. 

DISTILLED  WATER  GELATINE. — Ten  per  cent, 
gelatine  in  distilled  water. 

NUTRIENT  GELATINE. — Nutrient  broth  con- 
taining 10  %  gelatine.  (In  hot  weather  15  or 
20  %  gelatine  is  necessary.)  After  the  gela- 
tine has  dissolved,  the  white  of  an  egg  is 
added,  the  vessel  placed  in  the  steriliser 
for  an  hour  before  nitration,  filtered,  stan- 
dardised, run  into  sterile  test  tubes  (10  c.c. 
into  each) ,  the  tubes  plugged  with  sterile  wool, 
and  steamed  for  20  minutes  on  three  suc- 
cessive days. 

NUTRIENT  BROTH. — An  infusion  of  1  Ib. 
of  gravy  beef  free  from  fat  in  a  litre  of  tap 
water  is  known  as  acid  beef  broth.  When 
rendered  alkaline  and  salt  peptone  added 
nutrient  broth  is  obtained.  For  most  pur- 
poses Lemco  can  be  substituted  for  beef.  This 
allows  a  broth  of  a  more  constant  composi- 
tion, although  many  workers  prefer  the  use  of 
beef  broth  for  the  preparation  of  nutrient 
gelatine.  A  useful  broth  may  be  made  from 
10  to  20  grammes  of  Lemco,  10  to  20  grammes 
of  Witte's  peptone,  5  to  10  grammes  of  salt, 
and  a  litre  of  water.  To  this  gelatine  or  agar 
may  be  added,  or  it  may  be  standardised  to 
+  10  reaction  and  used  as  broth. 

NUTRIENT  AGAR. — This  is  prepared  in  the 
same  way  as  nutrient  gelatine,  1^  %  agar 
being  substituted  for  gelatine. 


BILE-SALT  BROTH  (MACCONKEY  &  HILL'S 
MEDIUM). — Sodium  taurocholate  0'5  gramme, 
peptone  2  grammes,  and  glucose  (or  lactose) 
0'5  gramme,  are  dissolved  in  100  c.c.  of 
water,  filtered,  and  neutral  litmus  solution 
added  to  give  a  distinct  blue  colour.  This 
strength  is  known  as  "  single  strength," 
and  is  used  for  amounts  of  1  c.c.  and 
under  of  water.  Some  media  of  "double 
strength  "  is  also  prepared  and  measured  in 
amounts  of  10  c.c.  and  20  c.c.  into  Durham's 
tubes  for  the  reception  of  similar  amounts  of 
water.  (Durham's  tubes  are  test  tubes,  of 
various  sizes,  containing  small  inverted  tubes 
which  become  filled  with  liquid  during  sterilisa- 
tion, and  when  an  organism  ferments  a  con- 
stituent of  the  media  with  production  of  gas  ; 
this  gas  is  observed  in  the  inner  tube.) 

CONRADI-DRIGALSKI  AGAR. — This  medium  is 
very  tedious  to  prepare,  and  is  best  purchased. 
PEPTONE  WATER. — 1  %  Witte's  peptone 
and  ^  %  common  salt  in  water.  After 
heating  to  dissolve  the  peptone,  it  is  made 
faintly  alkaline.  From  1  to -2  %  of  glucose, 
lactose,  mannite,  saccharose,  dulcite,  or  other 
carbohydrates  may  be  added,  the  medium 
tinged  with  litmus  and  used  for  the  differentia- 
tion of  the  varieties  of  B.  coli,  B.  typliosus,  &c. 
MILK. — Separated  milk  just  neutralised  with 
sodium  carbonate  and  sterilised  for  an  hour  on 
three  successive  days.  This  may  be  tinged 
with  litmus.  (Litmus  milk.) 

NEUTRAL  RED  BROTH. — One-half  per  cent, 
solution  of  Griibler's  neutral  red  in  water  is 
added  in  the  proportion  of  1  c.c.  to  every 
10  c.c.  of  aglucose  broth  containing  ^  %  glucose. 

W.  P. 

Water,  Sampling  of. — When  taking  a 
sample  of  a  house  supply  the  tap  should  be 
allowed  to  run  for  5  or  10  minutes  first,  but 
when  an  examination  for  lead  is  to  be  done 
the  first  runnings  from  the  tap  in  the  morning 
must  be  tested.  When  a  public  supply  is  to 
be  examined  the  sample  should  be  collected 
from  a  hydrant  in  direct  connection  with  a 
main.  A  sample  from  a  river,  lake,  or 
reservoir  should  be  taken  some  distance  from 


JI.S.E. 


513 


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the  banks,  care  being  taken  to  exclude  any 
floating  scum  and  avoiding  the  stirring  up  of 
mud.  The  quantity  required  for  the  chemical 
analysis  is  half  a  gallon.  The  sample  should 
be  taken  in  a  Winchester  quart  bottle,  which 
should  have  a  glass  stopper,  and  should  be 
first  washed  with  strong  sulphuric  acid  and 
then  rinsed  with  distilled  water  until  free  from 
acidity.  The  bottle  should  be  rinsed  two  or 
three  times  with  the  sample  before  filling. 
No  sealing-wax,  linseed  paste,  or  other  form 
of  sealing  material  should  be  used,  but  the 
stopper  should  be  tied  down  with  a  piece  of 
parchment  paper  or  clean  rag.  The  bottle 
should  be  packed  in  straw  or  other  suitable 
material  and  sent  off  to  the  analyst  with  the 
least  possible  delay.  Particulars  of  the  date 
of  collection,  the  source  of  the  sample,  and 
the  proximity  of  sources  of  possible  pollution 
should  be  given.  In  the  case  of  a  well  the 
depth  and  particulars  of  the  strata  should  be 
given.  When  a  bacteriological  examination 
is  needed  a  special  sample  must  be  taken. 
The  bacteriologist  who  is  to  perform  the 
analysis  will  always  prefer  to  send  a  bottle, 
as  he  can  then  be  certain  of  its  sterility. 
The  bottle  should  contain  at  least  200  c.c., 
and  should  be  sterilised  by  heat.  When 
taken  from  a  tap  the  water  should  be  allowed 
to  run  for  10  minutes  first,  and  when  taken 
from  a  tank  or  other  body  of  water  the 
stopper  should  be  removed  about  a  foot  below 
the  surface.  The  sample  of  a  supply  should 
be  taken  direct  from  the  main,  as  in  passing 
through  a  cistern  an  increase  of  the  number 
of  bacteria  may  occur.  If  possible  the  sample 
should  reach  the  bacteriologist  within  3 
hours  of  collection,  and  should  be  packed  in 
ice  and  sawdust  if  further  delay  is  unavoidable. 
This  cooling  of  the  sample  will  to  a  certain 
extent  inhibit  the  multiplication  of  bacteria, 
but  even  when  so  packed  it  is  necessary  to 
limit  the  interim  between  collection  and 
examination  as  much  as  possible.  When 
II.  Welcldi  is  to  be  sought  for  an  extra  litre 
of  the  sample  should  also  be  taken,  and  when 
suspected  of  conveying  typhoid  a  Winchester 
quart  sample  should  be  supplied.  Every 


precaution  should  be  taken  to  preclude  the 
entrance  of  extraneous  organisms  during  the 
collection,  and  the  hands  should  not  come  in 
contact  with  the  portion  of  the  stopper  going 
in  the  bottle  or  with  the  mouth  of  the  bottle. 

W.  P. 

Water-Carriage  System. — The  water- 
carriage  system  is  the  method  of  removing 
solid  excreta  by  means  of  a  flow  of  water,  as 
opposed  to  its  collection  in  a  dry  state  in  pans 
or  privies  (see  "  CONSERVANCY  SYSTEMS  ") 
or  with  water  in  cesspools.  It  involves  the 
use  of  water-closets,  flushed  sometimes  by 
means  of  the  household  slops,  but  in  the  vast 
majority  of  cases  by  an  independent  supply  of 
water,  and  of  a  system  of  underground  pipes. 
The  latter,  when  serving  single  houses,  are 
known  as  "  drains,"  and  when  serving  a 
number  of  houses  as  "  sewers."  These  convey 
also  the  household  slops  and  water  soiled  by 
use  in  factories,  &c.,  and  generally  the  whole 
or  a  part  of  the  rain-water.  (See  also  "  WATER- 
CLOSETS,"  "DRAINS,"  "  SEWERS,"  "  THE  COM- 
BINED SYSTEM,"  "  THE  SEPARATE  SYSTEM.") 

A.  J.  M. 

Water-Closets. — The  conditions  required 
in  these  fittings  are  cleanliness  and  safety. 
The  appliances  must  therefore  be  so  con- 
structed and  designed  as  to  expose  no  surfaces 
liable  to  be  soiled  without  the  certainty  of 


FIG.  1. — Wash-down  Closet. 

them  being  cleaned.  They  must  also  retain 
a  sufficient  volume  of  water  and  expose  an 
adequate  area  thereof  to  insure  the  immediate 
and  complete  immersion  of  fsecal  matter,  in 
order  that  this  may  be  prevented  from  staining 
the  basin  and  from  giving  off  bad  odours. 
At  the  same  time  the  water  retained  in  the 
basin  must  not  be  too  great  in  quantity  to  be 


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entirely  changed  by  an  ordinary  flush  of  water 
from  the  cistern  connected  to  the  closet. 
The  efficiency  of  the  closet  trap  must  further 
be  considered  as  forming  a  component  part  of 
the  desirability  of  the  closet  as  a  whole.  The 


FIG.  2. — Siphonic  Pedestal  Closet. 


Pedestal  closets  ; 


only    sanitary   forms   of    closets    at   present 
available  are  : — 

1.  Wash-down) 

2.  Siphonic      / 

3.  Corbel  closets ;  and 

4.  Yalve  closets. 

These  are  all  made  in  a  variety  of  forms 
but  differ  only  in  detail.  For  typical  speci- 
mens, see  Figs.  1  to  4.  The  wash-down, 
closet  is  the  best  form  of  closet  apparatus 
to  be  had  for  general  purposes.  It  is  equally 
suitable  for  the  tenement  of  the  poor  and  the 
mansion  of  the  rich.  It  may  be  made  use 
of  for  either  a  ladies'  or  a  gentlemen's  closet, 
and  when  in  a  suitable  position  may  also  be 
utilised  as  a  "  slop-hopper,"  as  well  as  for 
the  purpose  for  which  it  is  primarily  intended. 
In  selecting  a  closet  of  this  type,  the  chief 
points  to  be  attended  to  are,  as  already  stated, 
the  area,  depth,  and  position  of  the  water 
retained  in  the  basin  and  the  depth  of  the 
"  seal  "  of  the  closet  trap.  The  flushing  rim 
should  be  such  that,  in  flushing,  every  portion 
of  the  interior  of  the  basin  is  washed,  and 
that  the  water  forms  a  jet  or  cascade  directed 
towards  the  outlet.  This  latter  is  necessary 
to  force  fsecal  matter  out  of  the  basin.  The 
inside  surfaces  of  the  basin  should,  of  course, 
be  perfectly  smooth,  and  as  white  and  free 
from  ornament  as  possible.  The  various 
designs  of  flowers,  &c.,  with  which  the  interior 


of  closets  are  frequently  decorated  only  tend 
to  conceal  dirt.  Similarly,  in  order  to  avoid 
accumulations  of  dust  and  other  impurities, 
the  outer  surfaces  of  these  and  all  other  forms 
of  closets  should  be  free  from  all  raised  orna- 
mentation, and  preferably  also  perfectly  white. 
Lastly — and  this  is  of  great  importance — the 


FIG.  3. — Corbel  Closet. 

outlet  arm  of  the  closet  trap  should  be  so 
formed  and  placed  that,  whatever  may  be  its 
connection  with  the  drain  or  soil  pipe,  the 
joint  will  be  in  view  and  easily  accessible. 
This  is  necessary  both  in  order  that  the  joint 
may  be  made  in  the  first  place,  and  that,  subse- 
quently, any  damage  which  might  occur  to 
the  joint  will  be  readily  noticed.  The  Corbel 
closet  is  identical  with  the  wash-down,  with 
the  exception  that  it  projects  from  the  wall 
into  which  it  is  built  instead  of  standing  on 
the  floor.  Siphonic  closets  are  also  very 
similar  in  appearance  and  general  design  to 
wash-down.  The  material  difference  is  that 
their  contents  are  siphoned  out  of  the  basins 
instead  of  being  flushed  out  when  the  water 
in  the  cistern  is  discharged.  This  is  brought 
about  by  discharging  a  portion  of  the  flushing 
water  on  the  outlet  side  of  the  trap  of  the 
basin,  a  vacuum  being  thereby  created.  When 
of  good  type,  siphonic  closets  are  very  desirable 
fittings,  as  they  make  a  full  use  of  the  avail- 
able flushing  water  and  are  practically 
noiseless. 

In  valve  closets  the  water  is  retained  in  the 
basin  by  means  of  a  valve  or  flap  at  its  outlet. 
The  following  points  should  be  attended  to 
in  choosing  them  : — 

1.  The  overflow  arm  should  be  open  at  the 
top,  to  permit  of  cleansing  by  hand. 


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2.  The  overflow  arm  should  be  trapped  and 
arranged  to  receive  a  small  quantity  of  water 
whenever  the  basin  is  flushed. 

3.  The   valve    should    be   so  placed   that, 
when  opened,  it  will  cover  the  outlet  of  the 
overflow  arm  where  the  latter  joins  the  valve 
box,  in  order  to  preclude  the  possibility  of 
paper,  &c.,  finding  its  way  into  the  overflow 
pipe  and  thus  choke  it. 

4.  A  ventilation  pipe  (usually  known  as  a 
"  puff"  pipe)  should  be  provided  on  the  valve 
box. 

5.  The    valve    box    should    be    porcelain 
enamelled  in  its  interior. 

6.  The  working  parts  of  the  valve  should 
be  as  simple  and  as  strong  as  possible,  and 
such  as  to   insure  its  proper  closing  at  all 
times. 

7.  The  flushing-rim  should  be  continuous 
all  round  the  basin,  which  should  never  be 
flushed  by  means  of  a  "  fanspreader." 

8.  The  water-supply  valve  (and  service  pipe 
thereto)  should  never  be  less  than  1J  in.  in 
diameter.     Where  the  available  head  of  water 
is  less  than  10   ft.,  it  should  be    1J  in.  in 
diameter. 

9.  A   drawn   lead   siphon  trap    should   be 
provided  immediately  under   the  valve  box, 


PIG.  4.— Valve  Closet. 

in  order  to  disconnect  the  closet  from  the 
soil  pipe.  The  valve  alone  is  insufficient  for 
this  purpose,  although  it  offers  additional 
security.  G.  J.  G.  J. 

Water-Hammer. — The  concussion  caused 
in  water  mains  and  fittings  when  running 
water  is  suddenly  stopped  by  the  closing  of 


a  valve  or  cock.  This  concussion  may  work 
loose  holdfasts  and  cause  water  pipes  to  burst 
or  split.  That  the  water  pressure  is  greatly 
increased  under  these  circumstances  is  shown 
by  the  following  figures  published  by  Sir 
Alexander  Binnie,  as  a  result  of  experiments 
carried  out  by  him  : — 


Pressure  in  Ibs.  per  sq.  in. 

Tap. 

Main. 

Before  opening  tap 
When  open 
When  shut  quickly 

125 
20 
550 

125 

120 
220 

Water  Meters. — Domestic  supplies  of 
water  are  usually  charged  for  in  England  on 
the  basis  of  a  certain  percentage  on  the 
annual  rateable  value  of  the  premises,  ranging 
from  about  5  °/0  on  the  larger  properties  to 
7  %  on  those  of  small  rentals,  but  no  fixed 
rule  obtains.  Large  trade,  garden,  and  other 
supplies  are  mostly  measured  by  meter, 
and  charged  for  according  to  the  quantity 
used.  Water  meters  may  be  classified  under 
three  heads,  viz. :  positive  or  piston  meters, 
inferential  or  turbine  meters,  and  volume  or 
capacity  meters. 

In  the  positive  meter  the  actual  quantity  of 
water  supplied  is  measured  by  admitting  it 
into  a  cylinder  of  known  capacity,  at  the  top 
and  bottom,  alternately,  of  a  piston,  thus 
causing  it  to  move  up  and  down  in  the 
cylinder,  the  strokes  made  by  the  piston 
being  recorded  upon  a  dial  face  by  means  of 
suitable  wheel- work. 

Inferential  meters  contain  a  small  turbine 
which  is  worked  by  the  current  of  water 
passing  through  the  meter  ;  the  registration 
is  based  upon  the  assumption  that  the  rate  of 
rotation  of  the  turbine  is  proportionate  to  the 
velocity  of  influx  of  the  current  of  water, 
and  the  revolutions  are  recorded  by  suitable 
mechanism  as  before. 

Volume  or  capacity  meters  are  largely  used 
in  the  United  States  of  America,  and  to  a 


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limited  extent  in  this  country.  Broadly 
speaking,  they  consist  of  a  casing  of  gun- 
metal  or  vulcanite  in  which  works  a  vulcanite 
block,  serving  both  as  piston  and  valve.  An 
objection  frequently  raised  to  this  class  of 
meter  is  that  they  seldom  possess  any  pro- 
vision for  taking  up  wear,  and  that,  though 
intended  to  measure  the  volume  passing 
through  them  they  do  not  measure  small  flows. 
For  large  flows  they  are  said  to  be  very 
accurate,  and  possess  the  merits  of  simplicity, 
smallness,  and  cheapness.  For  the  "  Bee " 
meter,  which  is  of  the  disc  type,  it  is  also 
claimed  that  small  particles  of  foreign  matter 
may  pass  through  the  meter  without  wedging 
the  measuring  chamber.  This  meter  will  also 
run  with  a  very  small  "  head." 

Of  the  different  classes  of  meters,  those  of 
the  "  positive  "  class  are  the  most  accurate, 
and  correctly  record  very  small  flows  of  water. 
They  are,  however,  large  in  size,  expensive, 
and  occasionally  stop  owing  to  incrustation 
or  gritty  matter  passing  in  the  water,  thus 
cutting  off  the  supply  much  to  the  annoyance 
of  the  consumer.  On  the  other  hand,  should 
an  inferential  meter  stop  registering  the  water 
passing  through,  it  does  not  stop  the  supply, 
a  fact  which,  though  satisfactory  from  the  con- 
sumer's point  of  view,  is  obviously  the  reverse 
for  the  water  authority. 

Inferential  meters  may  sometimes  not 
revolve  under  a  small  flow  turned  on  very 
slowly,  but  are  sufficiently  accurate  for 
registering  ordinary  supplies  when  subject  to 
regular  inspection.  They  are  also  cheap  and 
of  small  size,  and  are  suitable  for  measuring 
large  trade  supplies  taken  at  a  fairly  uniform 
rate  ;  but  the  positive  meter  is  best  adapted  for 
correctly  recording  small  consumptions.  (See 
also  "  YENTURI  METER"  and  "  WATER  SUPPLY, 
PREVENTION  OF  WASTE  "  (Deacon's  meter).) 

W.  H.  M. 


Water  Power. — The  power  of  a  waterfall 
is  governed  by  two  things  :  the  quantity,  and 
therefore  the  weight,  of  water  flowing  in  a 
given  time,  and  the  "  head  "  or  vertical  height 


through  which  it  descends.     The  theoretical 
horse-power  will  be  equal  to 
62-4  Q  H 
33,000   ' 

Q  =  Quantity  of  water  in  cubic  feet  per 
minute. 

H  =  Head  of  water  from  tail  race  in  feet. 

The  available  power  will  depend  upon  the 
efficiency  of  the  motor  and  the  conditions 
under  which  it  is  installed  (see  "TURBINES"  and 
" WATER-WHEELS,"  also  "HEAD  PRESSURE, 
LOSS  OF  ").  Q  may  be  ascertained  by  measure- 
ment over  a  weir  or  estimated  from  the 
sectional  area  and  velocity  of  the  stream  (see 
"  GAUGING  OF  STREAMS.")  H  should  be  taken 
concurrently  (see  "HYDROSTATIC  HEAD"). 

E.  L.  B. 

Water-Seal.     (See  "TRAP.") 

Watershed  or  Catchment   Area.  —  A 

tract  of  country  the  rainfall  upon  which 
gravitates  naturally  to  one  common  water- 
course or  outlet.  Every  river  or  stream  has 
its  own  contributory  watershed  from  which  the 
supply  of  water  is  derived.  (See  "  WATER- 
SUPPLY.") 

Water  Supply,  Domestic. — The  principal 
points  requiring  attention  in  domestic  water 
supplies  are  those  relating  to  storage,  quantity, 
distribution,  and  nitration.  Koughly,  the 
amount  of  water  necessary  for  various  domestic 
requirements  is  as  follows  : — 

For  each  person,  per  diem          .     25  gallons. 

,,       „  horse   .         .         .         .     15  ,, 

,,       ,,  pony,  donkey,  or  mule       6  ,, 

,,       ,,  head  of  cattle       .                8  ,, 

,,  sheep  or  pig         .         .1  ,, 

,,       ,,  2- wheel  carriage  .         .8  ,, 

,,  4-wheel        „  .15 

,,       ,,  square  yard  of  garden  .       OJ  ,, 

For  fire-extinguishing  purposes,  200  gallons 
per  minute  for  30  minutes.  According  to 
Dr.  Parkes,  the  amount  of  water  used  per 
head  in  a  family  of  fairly  cleanly  people  is  as 
follows  : — 


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Cooking 0'75  gallons. 

Fluid    as    drink    (water,    tea, 

coffee,  &c.)    ....     0-33       „ 
Ablution,     including    a     daily 

sponge  bath,  taking  2^  to  3 

gallons          .         .         .  5'0       „ 

Share    of    utensil    and    house 

washing        ....       3'0       „ 
Share     of     clothes     (laundry) 

washing       ....       3'0       ,, 


Total,  say        .       12  gallons. 

With  fixed  baths  and  water-closets  this  is 
insufficient,  and  25  gallons  must  be  allowed 
as  a  minimum. 

The  materials  of  the  piping  used  for  the 
conveyance  of  water  through  the  house  must 
be  chosen  with  due  regard  to  its  nature,  more 
especially  when  the  water  is  such  as  will  act 
upon  lead.  Lead  is  the  chief  mineral  impurity 
to  be  guarded  against  in  a  domestic  water 
supply,  and  certainly  the  most  dangerous.  It 
has  a  cumulative  poisonous  action,  and  when 
taken  continuously,  even  in  minute  quantities, 
accumulates  in  the  system  and  remains  in 
the  body  until  serious  illness,  and  frequently 
fatal  consequences,  ensue.  Amongst  others 
of  the  troubles  which  may  be  ascribed  to 
lead  poisoning  are:  anaemia,  constipation, 
"plumbism"  or  lead  colic,  and  local  paralysis. 
The  capacity  of  waters  for  dissolving  lead  and 
their  rapidity  of  action  varies  considerably. 
As  a  rule  the  softer  and  purer  the  water  the 
greater  the  danger  of  that  kind.  Cases  have 
occurred  in  which  the  action  has  been  so 
great  and  rapid  that  standing  all  night  in  the 
lead  service  pipes  has  been  sufficient  to  deter- 
mine the  presence  of  lead  in  poisonous 
quantities  in  the  water  in  the  morning.  On 
the  other  hand,  certain  soft  waters  which 
might  be  expected  to  dissolve  lead  have  little 
or  no  action  upon  that  metal.  Other  waters, 
owing  doubtless  to  seasonable  variations,  are 
operative  upon  lead  at  one  time  although 
inoperative  at  others.  The  action  of  water 
upon  lead  is  of  two  kinds :  the  one  leading  to 
a  solution  of  the  lead,  the  other  to  its  erosion 
and  deposit  in  a  loose  powdery  form,  which  is 


readily  swept  away  by  the  flow  of  water  and 
conveyed  to  the  consumer.     When  water  is 
known  or  suspected  to  have  a  plumbo-solvent 
action,  wrought  iron,  tin-lined    or    block-tin 
piping  should  be  employed  for  its  conveyance. 
Wrought-iron   pipes   have   the   disadvantage, 
however,    that   they   rapidly   corrode   in   the 
interior  if  of  small  bore,  and  that  they  also 
suffer    considerably  from  outward  corrosion. 
The  water  flowing  through  them  is  also  apt  to 
become   discoloured  by   rust,  which,    though 
perhaps   harmless   in   itself    and    only   tem- 
porary in  many  cases,  is  nevertheless  notice- 
able and  objectionable  to  taste  and  sight.     If 
iron  pipes  are  used  they  should  be  lined  with 
a   continuous   tube   of    tin.      Tin-lined   tees, 
bends,  connectors,  and  other  fittings  are  avail- 
able, and  should  be  used  in  connection  with 
them.      Galvanised   wrought-iron    piping    is 
unsuitable    for    the    conveyance    of    potable 
water,  as   almost   all  waters — both   soft  and 
hard — have  a  solvent    action    upon  the  zinc 
coating  of  the  pipes  ;  and  all  zinc  salts  are 
poisonous.     Zinc   poisoning,    although    occa- 
sionally fatal,  is  not,  however,  as  serious  as 
lead  poisoning,  nor  are  its  effects  cumulative. 
Block-tin  pipes,  although  in  most  respects  the 
most  satisfactory,  are,  perhaps,  too  costly  for 
use  in  all  cases.     A  cheaper  piping  is  lead- 
incased   tin    piping,    which    consists    of    an 
internal  pipe  of  tin,  varying  from  one-thirty- 
second  to  one-sixteenth  of  an  inch  in  thickness, 
covered  by  an  outer  pipe  of  lead.     Such  pipes 
are  made  in  all  the  usual  sizes  and  strengths. 
Great  care  is  necessary  in  their  selection,  as 
seams  or  blisters  on  the  inner  surfaces  of  the 
pipes  and  other  faults  in  the  tin  lining  occur. 
The   continuity   of    the   tin   lining   must   be 
preserved,    so    that    no    lead   is    brought   in 
contact  with  the  water.     Great  care  is  neces- 
sary in  making  joints  on  this  kind  of  piping, 
as  the  tin  melts  inside  the  pipe  unless  the 
joints  are  made  with  great  dexterity.     Nor  is 
there  any  method  of  preventing  a  shrinkage 
of  the  tin  on  applying  the  heat  necessary  for 
making  a  joint  on  the  lead  pipe,  even  if  the 
molten   tin   is   prevented  from   blocking  the 
pipe.     So  liable  are  joints  on  lead-incased  tin 


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pipes  to  prove  unsatisfactory,  that  it  is  well  to 
join  the  pipes  in  all  cases  by  means  of  the 
special  connectors  made  for  the  purpose. 
These  are  made  on  the  principle  of  a  cap  and 
lining  connection,  and  join  the  pipes  without 
the  use  of  solder  or  heat. 

When  water  is  not  lead  -  solvent,  lead 
piping  may  be  safely  made  use  of,  and  will 
prove  the  most  convenient  to  handle  and  fix, 
as  it  may  be  taken  in  all  directions  without 
the  use  of  special  bends.  The  water  com- 
panies' regulations  as  to  strength  must,  how- 
ever be  complied  with.  As  will  be  seen  from 
the  following  table,  the  requirements  vary 
greatly  in  different  districts  : — 

WEIGHTS  OF  SERVICE  PIPES,  IN  LBS.  PER  LINEAL 
YARD,  EEQUIRED  BY  VARIOUS  WATER  COMPANIES: — 


Name  of  Water  Company. 

Dinneter  of  Pipe  in  Inches. 

1 

* 

I 

1 

l 

1| 

London 

5      6 

H 

9 

12 

16 

Manchester  Corporation 

6 

— 

9 

12 

16 

Glasgow  (Loch  Katrine) 

7 

— 

10 

14 

18 

Sheffield  

5 

7 

9 

11 

16 

22i 

Norwich.  . 

5 

7 

9 

11 

16 

22$ 

Nottingham 

—     7 

— 

11 

16 

22 

Market  Harborough     .  . 

5      6 

7* 

11 

16 

20 

Kent 

__. 

5 

7 

9 

12 

—  • 

West  Surrey 

4 

5* 

— 

9 

14 

20 

Caterham 

5 

6 

8 

10 

14 

— 

Colne  Valley 

5 

7 

9 

11 

16 

—  • 

Sevenoaks  and  Tonbridge 

5 

7 

9 

12 

15 

Water  pipes,  whatever  the  material  of  which 
they  are  made,  should  be  carefully  fixed  to 
avoid  air-locking,  which  is  especially  frequent 
in  the  case  of  lead  pipes  that  have  not  been 
sufficiently  supported  and  which  have  in  con- 
sequence sagged.  The  pipes  should  all  be 
fixed  with  a  fall,  so  that  the  entire  system 
may  be  emptied  through  taps,  should  that  be 
necessary.  The  pipes  should  also  invariably 
be  fixed  on  inner  walls  to  protect  them  from 
frost,  and  where  this  is  impossible  special 
provision  should  be  made  to  prevent  freezing 
(see  "  FROST  ").  A  stop-cock  should  be  pro- 
vided at  the  point  where  the  main  enters  the 
house,  and  other  stop-cocks  so  placed  that 
each  section  of  the  water  supply  system  may 


be  shut  off  for  repairs  if  necessary  without 
entirely  cutting  off  the  water  supply  of  the 
house.  While  soft  water  may  be  dangerous, 
excessively  hard  water  frequently  proves  a 
nuisance,  by  reason  that  it  produces  soap 
curds,  and  causes  deposits  and  incrustations 
in  boilers  and  hot  water  pipes. 

Soap  curds  form  a  greasy,  slimy  deposit  in 
sinks  and  other  sanitary  fittings,  and  in  waste 
pipes  and  drains,  and  these  partly  block  the 
pipes  and  frequently  become  highly  offensive, 
besides  forming  one  of  the  minor  difficulties 
of  sewage  disposal. 

Incrustations  in  boilers,  hot  water  pipes 
and  kettles  increase  the  consumption  of  fuel 
and  tend  to  block  the  pipes,  which  may  sooner 
or  later  have  to  be  taken  out  and  cleaned  or 
renewed.  They  are  also  liable  to  become  a 
source  of  danger  by  causing  boiler  explosions, 
either  through  the  blockage  of  the  circulation 
pipes  or  by  the  cracking  of  the  crust  within 
the  boiler,  which  would  permit  cold  water  to 
come  into  sudden  contact  with  the  highly 
heated  iron  of  the  boiler.  In  certain  cases  it 
is,  therefore,  desirable  to  partly  soften  the 
water  before  use  by  removing  the  temporary 
hardness.  This,  indeed,  is  the  only  portion 
of  the  hardness  which  can  be  conveniently 
removed,  as  permanent  hardness  can  only  be 
eliminated  by  the  introduction  of  substances 
which  would  render  the  water  unfit  for  diet- 
etic purposes.  Temporary  hardness  may  be 
removed  by  Dr.  Clark's  well-known  process, 
which  consists  of  the  addition  of  1  cz.  of 
quicklime  for  each  degree  of  hardness  to  every 
700  gallons  of  water.  This  lime,  by  combin- 
ing with  the  bicarbonate  held  in  solution  in 
the  water,  reduces  the  latter  to  the  form  of  a 
carbonate,  which,  being  insoluble  in  water,  is 
precipitated.  Continuously  working  apparatus 
for  the  purpose  are  made  by  various  makers, 
and  answer  the  purpose  well  if  attended  to 
periodically. 

Impurities  in  suspension,  if  they  exist  in 
water  in  a  building,  can  do  so  only  as  the 
result  of  shortcomings  on  the  part  of  the 
authority  supplying  the  water  or  of  the  house- 
holder. The  impurities  are  various,  and  may 


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range  from  particles  of  dust  to  small  fish. 
Nevertheless,  even  where,  as  doubtless  in  most 
cases,  the  filtration  of  the  public  water  supply 
is  carefully  attended  to,  it  must  be  remembered 
that  there  are  times  at  which  filtration  is  not 
perfect.  Such,  for  instance,  would  be  the 
case  during  severe  frosts  and  during  the  first 
day  or  two  on  which  a  filter  bed  is  used.  Nor 
are  filters  always  effective  in  removing  bac- 
teria. All  natural  water  contains  them,  in 
common  with  air,  food,  and  even  our  tissues, 
and  the  vast  majority  of  them  are  harmless 
or  even  beneficial.  The  danger  lies  in  the  few 
bacteria  which  are  branded  as  "  disease 
germs,"  which  (though  as  a  rule  absent)  may 
at  any  moment  be  found  in  drinking  water. 
To  remove  these  and  any  suspended  impurities 
which  might  be  present  in  domestic  drinking 
water,  it  is  a  wise  precaution  to  resort  to 
household  filtration  in  almost  all  cases,  pro- 
vided, of  course,  such  a  process  is  properly 
carried  out  and  regularly  attended  to. 

Whilst  it  is  desirable  that  water  should  be 
rendered  clear  and  sparkling,  the  most  impor- 
tant functions  to  be  expected  from  a  domestic 
filter  are : — 

1.  That  it  should  prevent  the  passage  of 
pathogenic  or  disease-producing  bacteria ;  and 

2.  That  it  must  add  no  fresh  impurity  or 
bacteria  to  the  filtrate. 

In  these  two  all-important  requirements 
many  of  the  filters  now  upon  the  market 
utterly  fail.  Their  filtering  mediums,  so  far 
from  being  capable  of  arresting  bacteria, 
rather  favour  their  propagation  and  multi- 
plication by  providing  a  suitable  nidus  for 
their  development.  Water  passed  through 
such  a  filter,  if  this  has  not  been  frequently 
cleaned  and  sterilised,  is  apt  to  be  far  more 
dangerous  than  unfiltered  water.  In  order  to 
gain  some  knowledge  as  to  the  relative 
efficiency  of  filters,  Drs.  Sims  Woodhead  and 
Cartwright  Wood  some  years  ago  carried 
out  a  series  of  valuable  experiments  by  sub- 
jecting all  known  filters  to  stringent  tests  by 
passing  pathogenic  organisms  through  them. 
As  a  result  of  these  experiments,  which  con- 
firmed previous  investigations  by  continental 


authorities,  the  investigators  gave  it  as  their 
opinion  that  the  only  forms  of  filters  which 
did  not  admit  the  passage  of  disease  germs 
were  the  candle  filters  known  as  the  "  Pasteur- 
Chamberland,"  the  "  Berkefeld,"  the  "  Aeri- 
Filtre  Mallie,"  the  "  Pukall "  filter,  Slack  & 
Brownlow's,  and  Duff's  Patent  Germ-Proof 
filters.  All  these  filters  are  fixed  to  the  mains 
and  the  water  drawn  through  them.  They 
need  only  be  made  use  of  for  drinking 
water. 

For  information  on  the  sources  and  con- 
struction of  works  of  water  supply  sec  "  WATER 
SUPPLY."  G.  J.  G.  J. 

Water  Supply  (General).— Rainfall  - 
Evaporation  and  Percolation — Classification  of 
Sources  of  Supply— Springs  and  Deep  Well 
Water— Upland  Surface  Waters— Surface  Water 
from  Cultivated  Land — River  Water— Quantity 
of  Water  per  Head  of  Population — Character 
of  Water  and  Causes  of  Impurity — Physical 
Characteristics — Action  of  Water  on  Lead — 
Construction  of  Waterworks — Catchment  Areas 
and  Storage — Compensation  Water — Gravitation 
Supplies — Waste  Weir,  &c.— Outlets  and  Valve 
Towers — Siphon  Outlets— Creeping  Flange- 
Aqueducts — Service  Reservoirs — Distribution  of 
Water — Intermittent  and  Constant  Supplies — 
— Prevention  of  Waste — Fire  —  Pipes  —  Dual 
Supplies — Water  Main  Scraping. 

WATER  SUPPLY  (GENERAL). — According  to 
the  census  of  1901  the  population  of  England 
and  Wales  was  about  32£  millions  of  people. 
This  involves  a  water  consumption  of, 
approximately,  1,000  million  gallons  per  day, 
calculating  upon  the  basis  of  80  gallons  per 
head  per  day.  At  Qd.  per  1,000  gallons, 
this  volume  of  water  represents  an  annual 
value  of  over  A'9,000,000.  It  will  be  seen, 
therefore,  that  the  collection,  treatment, 
and  distribution  of  so  large  a  quantity  of 
water  is,  necessarily,  a  work  of  very  consider- 
able importance,  especially  having  regard  to 
the  fact  that  the  business  of  obtaining  reliable 
sources  of  supply  to  meet  the  continual  growth 
of  population  is  a  matter  of  ever-increasing 
difficulty,  particularly  in  droughty  periods, 


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such  as  were  experienced   during   the   years 
1900  to  1902. 

RAINFALL  :  SOURCES  OF  WATER  SUPPLY. — 
All  supplies  of  fresh  water  come  primarily 
from  rainfall,  although  collected  under  varying 
circumstances  from  river,  lake,  underground 
basins,  or  other  sources.  Water  is  obtained 
in  its  purest  form  by  distillation.  The  heat 
of  the  sun  is  continually  drawing  up  large 
quantities  of  moisture  from  the  surface  of  both 
land  and  sea,  thus  forming  clouds,  which,  in 
due  course,  return  their  water  to  the  earth  in 
a  purified  form.  The  water  supply  of  any 
district  therefore  depends  primarily  upon  the 
rainfall  of  the  locality,  and  the  extent  and 
character  of  the  gathering  ground  or  "  catch- 
ment area."  The  average  rainfall  of  the 
whole  of  England  and  Wales  is  about  33  to 
34  in.  per  annum,  but  varies  considerably 
according  to  local  circumstances.  The  fall  in 
any  given  district  depends  largely  upon  its 
geographical  position,  the  direction  of  the 
prevailing  winds,  and  the  distribution  of  hills, 
mountain  ranges,  forests,  &c.  That  in  the 
western  and  southern  parts  of  this  country  is 
considerably  in  excess  of  the  fall  in  the  eastern 
counties.  The  rainfall  on  the  western  coast 
varies  from  40  to  70  in.  per  annum,  and 
as  an  exceptional  instance,  190'28  in.  were 
registered  at  Stye,  in  Cumberland,  in  1883. 
On  the  eastern  coast  from  20  to  30  in. 
may  be  taken  as  the  average,  but  in  the  year 
1901,  which,  for  England  and  Wales,  showed 
an  average  deficiency  of  more  than  13  % 
there  were  several  places  recorded  in  the 
county  of  Essex  with  rainfalls  of  between  14 
and  15  in.  only.  The  year  1901  was 
followed  by  an  even  drier  year  which  resulted 
in  a  cumulative  deficiency 1  for  the  two  years 
in  England  and  Wales  of  31  %,  and  over  the 
British  Isles  as  a  whole  there  was  a  deficiency 
of  rainfall  in  these  two  years  equal  to  a 
quarter  of  one  year's  fall.  In  many  parts  this 
caused  something  approaching  a  water  famine, 
and  gave  great  anxiety  to  those  responsible 
for  the  management  of  water  supplies.  This 

1  Below   the    30-years'   average,   1870 — 99,    which     for 
England  and  Wales,  was  34'28  in. 


dry  period  was  followed  by  one  of  exceptional 
humidity — the  percentage  of  excess  of  rainfall 
in  1903  (above  the  average  1870—1899)  being 
approximately  28  °/0in  England,  and  33  %in 
Wales.  For  water  supply  purposes  it  is  the 
minimum  rainfall  upon  which  all  calculations 
must  be  based,  and  the  late  Mr.  G.  J.  Symons, 
F.R.S.,  has  given  the  following  limits  of 
fluctuation,  based  upon  the  results  of  a 
large  number  of  observations  extending  over 
many  years,  which  are  believed  to  be  within 
7  %  of  the  actual  fall,  viz. : — 

The  wettest  year  will  be  45  %  more  than 
the  average. 

The  driest  year  33  %  less  than  the  average. 

The  driest  two  consecutive  years  26  %  less 
than  the  average. 

And  the  driest  three  consecutive  years  21  % 
less  than  the  average.  In  providing  "storage" 
for  water  supply  purposes  it  is  found  to  be 
useless  to  attempt  to  equalise  supply  over  a 
longer  period  than  three  consecutive  dry 
years,  as  by  so  doing  there  would  be  many 
years  when  the  storage  reservoirs  would  not 
get  filled.  It  would  be  no  use,  for  example, 
to  provide  sufficient  storage  to  prevent  over- 
flow during  the  year  of  greatest  rainfall,  or 
even  the  mean  of  a  10, 15,  or  20-year  period, 
because  the  daily  addition  this  would  make  to 
the  yield  during  dry  years  would  not  be  com- 
mensurate with  the  cost  of  the  additional 
storage  capacity.  The  water  which  falls  in  the 
form  of  rain  is  ultimately  disposed  of  in  several 
ways.  That  which  runs  off  the  surface, 
generally  spoken  of  as  "  surface  water,"  eventu- 
ally joins  the  neighbouring  streams  and 
rivers,  unless  intercepted  and  impounded  in 
some  storage  reservoir,  as,  for  example,  at 
Vyrnwy,  in  North  Wales,  by  the  Corporation 
of  Liverpool,  and  at  the  Elan  Valley  (Mid- 
Wales)  by  the  Corporation  of  Birmingham. 
It  frequently  happens  that  surface  water 
flowing  from  a  watershed  or  catchment  area 
consisting  largely  of  cultivated  lands,  and 
containing  a  considerable  population,  becomes 
seriously  polluted,  as  is  the  case  with  waters 
of  this  class  coming  from  the  watershed  of 
the  river  Thames. 


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EVAPORATION  AND  PERCOLATION.  —  Another 
part  of  the  rainfall  is  lost  by  evaporation,  or 
is  absorbed  by  trees  and  plants  to  form  part 
of  their  tissues ;  and  a  third  part  percolates 
into  the  earth  and  ultimately  joins  the  store 
of  underground  water  recoverable  for  use  by 
pumping,  or  part  of  which  may  reappear  in 
the  form  of  "  springs,"  possibly  at  very  distant 
points.  The  relative  amounts  of  water  dis- 
appearing in  the  above  ways  vary  according 
to  the  nature  of  the  soil,  the  contour  of  the 
land,  and  the  season  of  the  year.  Rain  falling 
upon  a  highly  porous  material,  like  gravel, 
sand  or  chalk,  will  rapidly  disappear  by 
sinking  into  the  ground  ;  but,  if  the  district 
be  largely  composed  of  hard  rock  or  stiff  clay 
very  little  will  percolate  into  the  subsoil.  The 
district  around  Brighton,  consisting  as  it  does 
of  chalk,  is  almost  wholly  devoid  of  streams 
or  surface  water  of  any  kind,  the  whole  per- 
colating into  the  porous  chalk  and  thus  feeding 
the  underground  sources  from  w7hich  the  town 
derives  its  entire  supply.  Of  the  total  rainfall 
during  any  year,  the  most  important  is  that 
falling  during  the  winter  half ;  it  is  this  which 
replenishes  the  sources  of  water  supply 
depleted  during  the  summer.  That  falling 
during  the  warm  season  has  but  comparatively 
little  effect  owing  to  the  large  amount  drawn 
off  by  evaporation.  Summer  rain,  however, 
reduces  the  demand  upon  the  waterworks  as, 
of  course,  the  daily  consumption  by  the  town 
is  less  during  showery  or  dull  weather.  It  is 
clear,  therefore,  that  the  period  of  the  year  in 
which  the  rain  falls  is  of  more  importance 
than  the  total  fall  of  the  year,  and  a  shortage 
is  more  likely  to  result  from  a  dry  winter  than 
from  a  dry  summer.  In  managing  storage 
water  it  is  very  desirable  not  to  draw  upon  it, 
if  possible,  until  late  in  the  summer  season, 
as  any  deficiency  in  the  supply  is  generally 
felt  towards  the  close  of  the  year.  Evapora- 
tion is  hastened  by  the  rain  falling  in 
numerous  separate  showers,  and  upon  an 
impermeable  soil ;  forests  and  vegetation 
afford  considerable  shelter  to  the  ground  and 
largely  protect  it  from  the  influence  of 
evaporation.  In  this  connection  it  may  be 


noted  that  the  Departmental  Committee 
appointed  in  1902  by  the  President  of  the 
Board  of  Agriculture  recommended  in  their 
report  "  that  the  attention  of  corporations 
and  municipalities  be  drawn  to  the  desirability 
of  planting  with  trees  the  catchment  areas  of 
their  water  supply."  The  percolation  of 
rainfall  into  the  surface  of  the  ground  depends 
largely  upon  the  geological  and  physical  con- 
ditions which  obtain.  It  depends  upon  the 
amount  of  rainfall,  the  porosity  of  the  surface 
strata,  and  the  slope  and  extent  of  the  per- 
meable surface.  It  varies  inversely  as  the 
evaporation  is  greatest  in  the  winter  season 
or  during  long  and  heavy  rains,  and  least  in 
warm  and  showery  weather.  The  question  of 
the  degree  of  percolation  has  a  direct  bearing 
upon  that  of  the  level  of  water  in  wells  and 
borings,  and  of  ground- water  in  general — the 
annual  rise  and  fall  of  which  is  frequently 
termed  "  seasonal  variation." 

CLASSIFICATION  OF  SOURCES  OF  SUPPLY. — 
The  different  sources  from  which  supplies  may 
be  obtained  have  been  classified  by  the  Rivers 
Pollution  Commissioners  in  their  sixth  report 
in  the  following  manner  : — 


Wholesome 


Suspicious 


Dangerous 


1.  Spring  water  . .          . .  )  Very 

2.  Deep  well  water       . .  j  palatable. 

3.  Upland  surface  water  \  Moderately 

4.  Stored  rain  water     . .  j  palatable. 

5.  Surface     water    from 

cultivated  land     .  . 

6.  Elver  water  to  which 


sewage  gains  access 
(  7.  Shallow  well  water  . . 


Palatable. 


SPRINGS  AND  DEEP  WELL  WATERS,  where 
available  in  sufficient  quantity,  as  a  rule  afford 
excellent  supplies,  but  in  some  cases  yield 
water  of  exceptional  hardness,  or  occasionally 
it  may  be  highly  impregnated  with  salt,  iron, 
or  other  constituents  which  render  it  unfit 
for  domestic  and  trade  purposes.  (See  article 
"  SPRINGS,"  "  WELLS,"  and  "  UNDERGROUND 
WATER.") 

UPLAND  SURFACE  WATERS. — These  waters  are 
collected  from  the  high  rocky  mountainous 
districts  of  WTales  and  the  north  of  England, 
and  Scotland,  which  afford  excellent  sources 


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MUNICIPAL   AND   SANITAEY   ENGINEEEING. 


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for  the  water  supply  of  large  towns  where  the 
appropriate  works  for  their  collection,  storage, 
and  in  some  cases  filtration,  have  been  carried 
out.  They  must  be  clearly  distinguished  from 
the  waters  flowing  from  low-level  catchment 
areas,  consisting  of  cultivated  lands  with  farm- 
steads, villages,  and  the  usual  rural  popula- 
tion, such  as  in  the  valley  of  the  Thames, 
where  much  of  the  water  reaching  the  river 
becomes  more  or  less  polluted  almost  at  its 
very  source.  For  the  supply  of  many  large 
towns  in  this  country,  upland  surface  water 
flowing  from  watersheds  consisting  of  the 
older  geological  formations  such  as  granite, 
the  Silurian  and  Devonian  strata,  mountain 
limestone,  &c.,  is  impounded  by  means  of 
large  earthen  or  masonry  dams  built  across 
the  valleys  of  the  upper  reaches  of  mountain 
streams.  Birmingham  has  carried  out  a  large 
scheme  of  this  description  at  Elan  Valley  (Mid- 
Wales)  to  supply  that  city  with  75,000,000 
gallons  of  water  per  day.  This  is  conveyed  to 
the  inhabitants  by  an  aqueduct  73  miles  in 
length.  Similar  water  undertakings  have 
been  carried  out  by  the  Liverpool  Corporation 
at  Vyrnwy  in  North  Wales,  by  Bradford  in  the 
Upper  Nidd  Valley  (Yorkshire),  by  Manchester 
at  Lake  Thirlmere  (Cumberland),  by  Glasgow 
at  Loch  Katrine  (Perthshire),  and  many 
other  towns  in  the  north.  A  large  gravitation 
scheme  for  the  utilisation  of  the  waters  of  the 
Upper  Wye  and  Usk  (Mid-Wales)  has  also 
been  seriously  proposed  for  the  better  supply 
of  London. 

Upland  surface  waters  of  this  character  are 
usually  almost  free  from  animal  impurities, 
are  peculiarly  soft,  but  sometimes  contain 
much  vegetable  or  peaty  matter.  In  a  series 
of  some  200  analyses  by  the  Elvers  Commis- 
sion, the  amount  of  dissolved  solids  in  upland 
surface  water  from  the  igneous  rocks  was 
ascertained  to  vary  from  about  1^  to  3  parts 
per  100,000,  about  15  parts  from  sandstones 
and  shales,  and  as  high  as  77'5  parts  in  water 
from  the  chalk  and  limestone  watersheds. 
There  was  an  almost  entire  absence  of  nitrates 
and  chlorides,  and  a  small  amount  only  of 
organic  nitrogen,  showing  the  organic  matter 


present  to  be  of  vegetable  origin  and  to  be 
derived  from  uncultivated  lands. 

The  larger  authorities  deriving  supplies 
from  upland  catchment  areas  usually  seek 
either  to  purchase  the  watersheds  or  to 
obtain  certain  rights  and  means  of  control 
of  the  contributory  areas,  in  order  that  the 
necessary  precautions  may  be  observed  and 
a  systematic  inspection  instituted,  to  safeguard 
the  water  supply  from  possible  pollution. 

EAIN  WATER. — In  rural  districts,  where 
better  means  of  supply  are  unattainable,  the 
collection  and  storage  of  rain  water  falling  on 
the  roofs  of  buildings  forms  a  valuable  source 
of  supply.  Some  of  the  disadvantages  in 
connection  with  its  utilisation,  however,  are 
the  many  precautions  necessary  to  prevent  its 
pollution,  the  uncertainty  of  the  rainfall,  the 
length  of  the  dry  season  from  year  to  year, 
and  the  large  size  of  the  reservoirs  necessary 
to  equalise  yield  and  supply. 

Eain  water  is  very  soft  and  well  aerated, 
and  when  not  contaminated -during  its  pre- 
cipitation, or  by  imperfect  methods  of  collection 
and  storage,  is  the  purest  of  all  natural 
waters.  In  the  immediate  neighbourhood  of 
towns,  however,  it  receives  many  impurities 
from  the  atmosphere,  including  organic 
matters,  germs,  sulphurous  and  sulphuric 
acids,  which  give  it  an  acid  reaction,  and 
large  quantities  of  tarry  and  carbonaceous 
matter  derived  from  the  combustion  of  coal. 
In  an  examination  of  London  rain  water, 
Angus  Smith  found  2  parts  per  100,000  of 
sulphuric  acid ;  4  to  5  parts  in  Manchester 
rain  water  ;  and  in  Glasgow  water  8  parts. 
It  therefore  happens  that  when  such  water 
falls  on  the  roofs  of  buildings  it  dissolves  lime, 
iron,  lead,  zinc,  &c.,  from  the  lead  and  zinc 
flats,  walls,  gutters  and  pipes,  and  also  con- 
tains much  soot  and  foreign  matters  settled 
upon  the  roof,  and  may  thus  become  very 
hard  and  impure.  Where  rain  water  is  used 
for  domestic  purposes,  the  roofs,  gutters,  &c., 
should  be  kept  quite  clean  and  free  from  dust, 
soot,  bird  droppings,  cats,  leaves,  and  other 
polluting  factors.  If  it  is  desired  to  use  the 
whole  available  rainfall  the  roofs  should  be 


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high-pitched  and  covered  with  an  impervious 
material,  such  as  good  Bangor  slates,  so  that 
there  may  be  a  minimum  of  loss  from  evapora- 
tion and  absorption.  The  quantity  of  water 
to  be  obtained  from  any  given  roof  or  other 
catchment  area  for  rain  water  will  depend 
principally  upon  the  average  rainfall  of  the 
district  and  the  area  of  the  roofing.  There 
will,  of  course,  be  small  losses  from  evapora- 
tion and  other  causes  to  be  deducted  from  the 
total.  Where  rainfall  statistics  are  not 
obtainable  the  figure  must  be  obtained  by 
means  of  a  rain-gauge  in  a  similar  manner  to 
that  followed  in  ascertaining  the  fall  on  a 
large  catchment  area  for  a  gravitation  scheme 
of  supply.  In  this  connection  the  "  Rules  for 
Rainfall  Observers,"  issued  by  the  "  British 
Rainfall  Organisation,"  founded  by  the  late 
G.  J.  Symons,  F.R.S.  should  be  followed. 
For  use  in  ordinary  localities  the  "  Snowdon 
rain-gauge  "  is  recommended.  It  is  3  in.  in 
diameter  and  easily  fixed  by  four  stakes  driven 
into  the  ground.  The  glass  measuring  jar 
when  filled  to  the  top  division  holds  half  an 
inch,  and  each  division  on  the  scale  marked 
thereon  denotes  one-hundredth  of  an  inch  of 
rain.  The  rain  is  conducted  by  a  funnel  to  a 
bottle  within  the  gauge,  and  the  previous 
day's  fall  should  be  measured  each  morning 
in  the  graduated  glass  and  duly  recorded. 

To  find  the  quantity  of  water  falling  upon 
any  roof  area,  the  following  formula  may  be 
applied  : — 

A  X  R  _     (Number  of  gallons  received 

277*274        1       by  the  roof  in  a  year. 
Where  A  =  the  area  of  roof  in  square  inches ; 

and  R  =  average  annual  rainfall  in  inches  ; 

and  277'274  =  cubic  inches  in  1  gallon  of 

water. 

Or  for  practical  purposes,  the  calculation 
may  be  made  by  multiplying  the  roof  area  in 
square  feet  by  the  annual  rainfall  in  inches 
and  then  by  '52.  This  is  practically  equal  to 
multiplying  the  roof  area  by  half  the  rainfall, 
and  in  this  simplified  form  the  rule  is  within 
4  %  of  the  true  quantity.  In  calculating 
roof  area  the  horizontal  area  must  be  used, 
not  the  area  as  taken  on  the  slope.  In 


England  the  average  amount  of  roof  area  per 
person  has  been  put  at  60  sq.  ft.,  and  if  we 
take  30  in.  as  the  average  annual  rainfall, 
this  gives  a  yield  per  person  of  935  gallons,  or 
2'5  gallons  per  day,  that  is  assuming  there  is 
no  loss  from  evaporation.  It  may  also  be 
useful  to  note  that  1  in.  of  rain  gives  4'673 
gallons  per  square  yard  of  surface,  or  22,617 
gallons  (equal  to  10]  tons)  of  water  to  the 
acre.  In  estimating  the  annual  yield  of 
water  from  rainfall  the  average  fall  of  the 
three  driest  years  is  a  safe  basis  to  calculate 
upon.  As  a  useful  practical  rule  for  ascertain- 
ing the  requisite  amount  of  storage  for  a  rain- 
water tank,  it  may  be  noted  that  the  minimum 
tank  capacity  to  be  provided  should  be  at 
least  capable  of  holding  one- fourth  the  annual 
rainfall.  Rain  water  may  be  stored  in  brick 
or  slate  storage  tanks,  built  either  above  or 
below  ground.  Fig.  1  shows  details  of  a 
suitable  tank,  built  underground,  in  either 
brick  or  concrete,  the  inside  being  rendered 
in  cement.  The  incoming  rain  water  passes 
through  a  fine  copper  wire  screen  fixed  at  A 
to  intercept  leaves  and  other  debris,  through 
a  sand  or  polarite  filter  at  B,  before  passing 
into  the  storage  tank,  and  the  suction  of  the 
pump  is  protected  with  a  fine  copper  gauze 
shield  at  C. 

SURFACE  WATER  FROM  CULTIVATED  LAND.— 
This  as  a  source  of  supply  can  only  at  best  be 
looked  upon  with  suspicion,  being  open  at  all 
times  to  dangerous  pollution.  It  should  not 
be  used  except  under  extreme  necessity.  The 
impurities  consist  largely  of  organic  pollution 
from  the  manuring  of  lands,  animals,  and 
human  wastes.  Any  such  waters  employed 
for  domestic  use  would  require  thorough 
subsidence  in  storage  reservoirs  and  efficient 
filtration  under  watchful  management  before 
being  delivered  for  public  supply.  There  are 
many  towns,  however,  that  still  take  their 
supplies  from  rivers  and  streams  which  con- 
sist very  largely  of  water  of  this  class,  whilsl 
many  others,  owing  to  the  growth  of  popula- 
tion and  increasing  pollution  of  the  water- 
courses, have  had  to  abandon  their  river 
supplies  altogether  or  extract  the  water  at  a 


524 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


WAT 


point  nearer  the  source  of  the  stream  before 
pollution  has  taken  place.  The  river  Tame 
was  originally  the  main  supply  to  Birming- 
ham, but  in  1869  it  had  become  so  polluted 
that  it  was  abandoned  for  domestic  use,  and 
many  other  similar  instances  may  be  cited. 

RIVER  WATER. — Much  that  has  been  said  of 
"  surface  water  from  cultivated  land  "  applies 
equally  to  river  waters.  On  the  use  of  river 
water  subjected  to  human  and  other  forms 
of  pollution  there  is,  however,  considerable 
diversity  of  opinion  as  to  how  far  it  is  safe 
for  large  populations  to  depend  thereon  for 
domestic  purposes  ;  but  with  respect  to  these 
sources  of  supply,  it  may  be  said  that  the 
bulk  of  medical  and  scientific  opinion  agrees 


Screen- 


^•Puddle 
FIG.  1. — Bain- water  Storage  Tank. 

that  the  drinking  water  of  a  large  town  ought 
not  to  be  obtained  from  rivers  and  streams 
passing  through  cultivated  and  inhabited 
lands.  Works  that  deal  with  this  class  of 
water  have  usually  been  long  established, 
and,  since  their  construction,  the  water- 
courses drawn  upon  have  as  a  rule  gradually 
become  more  and  more  polluted,  until  ulti- 
mately their  abandonment  will  doubtless 
become  a  necessity.  The  possible  means  of 
pollution  of  a  stream  flowing  through  culti- 
vated lands  are  so  very  numerous  that  the 
river  usually  becomes  in  effect  the  common 
sink  for  the  drainage  and  wastes  of  the  water- 
shed through  which  it  flows.  The  Rivers 
Pollution  Prevention  Acts  and  the  work  of 
River  Conservancy  Boards  have  minimised 
the  evil,  but  much  remains  to  be  done. 

The  opinion  of  the  Royal  Commissioners  on 
Water  Supply  (1892)  in  regard  to  the  use  of 


the  Thames,  which  receives  a  considerable 
amount  of  pollution  and  is  subject  to  frequent 
and  heavy  floods,  is  of  interest  in  this  con- 
nection. The  Commissioners  reported  : — 
"  We  are  strongly  of  opinion  that  the  water, 
as  supplied  to  the  consumer  in  London,  is  of 
a  very  high  standard  of  excellence  and  of 
purity,  and  that  it  is  suitable  in  quality  for 
all  household  purposes.  We  are  well  aware 
that  a  certain  prejudice  exists  against  the 
use  of  drinking  water  derived  from  the 
Thames  and  Lea  because  these  rivers  are 
liable  to  pollution,  however  perfect  the  subse- 
quent purification,  either  by  natural  or  artifi- 
cial means,  may  be ;  but  having  regard  to  the 
experience  of  London  during  the  last  30 
years  and  to  the  evidence  given  to  us  on  the 
subject,  we  do  not  believe  that  any  danger 
exists  of  the  spread  of  disease  by  the  use  of 
this  water,  provided  that  there  is  adequate 
storage,  and  that  the  water  is  efficiently 
filtered  before  delivery  to  the  consumers." 
In  the  same  year  (1892),  however,  occurred 
the  very  severe  epidemic  of  cholera  in  Ham- 
burg, which  admits  of  no  doubt  as  to  the 
agency  of  water  in  propagating  disease.  The 
cities  of  Hamburg  and  Altona  both  take  their 
water  supplies  from  the  River  Elbe — Altona 
from  a  point  some  7  miles  below  the  discharge 
of  the  sewage  of  both  cities,  and  Hamburg 
from  about  7  miles  above.  In  the  latter 
instance  the  water  taken  was  simply  passed 
through  ponds  or  settling  tanks,  but,  owing 
to  the  increase  in  the  demand  for  water  it  was 
pumped  through  too  rapidly  to  permit  of 
much  improvement  by  subsidence. 

At  Altona,  a  little  lower  down  the  river  but 
continuous  with  Hamburg,  the  water  wras 
filtered  through  sand.  The  condition  of  the 
raw  water  was  even  worse  than  that  at  Ham- 
burg, yet  in  Altona  only  328  persons  died, 
against  8,605  in  Hamburg.  The  boundary 
line  between  the  water  areas  of  Hamburg  and 
Altona  was  clearly  marked  out  in  places  by 
the  cases  of  cholera;  in  some  streets,  for 
example,  with  one  side  supplied  by  Hamburg 
and  the  other  side  by  Altona,  the  cholera 
stopped  at  the  dividing  line.  A  scheme  of 


525 


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ENCYCLOPAEDIA  OF 


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filter  beds  was  rapidly  pushed  forward  by 
Hamburg  and  brought  into  use  the  following 
year,  when  the  city  had  equal  immunity  from 
the  disease  except  for  a  short  period  when 
there  was  a  sudden  but  limited  rush  of  cases 
which  were  found  to  be  due  to  a  defect  in  the 
masonry  which  allowed  unfiltered  Elbe  water 
to  pass  into  the  supply.  The  beneficial  effects 
of  the  new  Hamburg  filters  and  of  those  at 
Altona  which  protected  that  city  from  a 
cholera  epidemic  in  1892  are  thus  demon- 
strated in  a  most  practical  and  instructive 
manner,  which  applies  also  to  the  6  millions 
of  people  in  "  Water  London." 

Amongst  other  large  centres  of  population 
depending  upon  river  supplies  may  be 
mentioned  Berlin,  New  York,  Chicago,  Boston, 
and  Philadelphia. 

The  natural  organic  purification  of  rivers 
during   their   flow   is    a   subject   which    has 
received   much   attention,   but   is   one   upon 
which  great  difference  of  opinion  exists.     It 
was   contended   by   the   late   Dr.    Tidy   that 
water    containing     20%    sewage   would,   in 
the    course    of    a     10    or    12    miles    flow, 
become  purified  by  natural  oxidation,  whilst, 
on   the   other   hand,   Dr.  E.  Frankland,  by 
experiments  on  the  rivers  Irwell  and  Thames, 
arrived  at  the  opinion  that  a  200  miles  flow 
would  be  insufficient  for  the  purpose.     After 
exhaustive  inquiries  the  Eoyal   Commission 
on    Elver  Pollution  of   1868   arrived   at  the 
conclusion  that  "  there   is   no   river   in   the 
United  Kingdom  long  enough   to   effect   the 
destruction  by  oxidation  of  sewage  put  into  it 
at    its   source."     The   principal   enactments, 
other  than  local  special  Acts,  dealing  with  the 
pollution  of  streams  arid  watercourses   are : 
The   Public   Health   Act,    1875;   the   Rivers 
Pollution  Prevention  Acts,  1876  and  1893; 
the  Waterworks  Clauses  Act,  1847  ;  the  Public 
Health    Acts   Amendment   Act,    1890;      the 
Local  Government  Act,  1888 ;  and  the  Public 
Health  (London)  Act,  1891. 

QUANTITY  OF  WATER  REQUIRED  PER  HEAD 
OF  POPULATION. — The  quantity  of  water  that 
must  be  provided  per  head  of  the  population 
is  a  fluctuating  amount  depending  largely 


upon  local  habits  and  conditions.  It  will 
vary  (1)  according  to  the  nature  of  the  locality, 
whether  residential  or  manufacturing  in 
character ;  (2)  the  method  of  drainage  of  the 
town,  whether  upon  the  "  water-carriage  " 
system  or  "  conservative  "  system ;  (3)  the 
amount  required  for  trade  purposes,  garden 
purposes,  carriage- washing,  &c.  ;  (4)  for 
municipal  purposes,  such  as  sewer  flushing, 
street  watering,  public  conveniences,  washing 
streets  and  pavements,  &c. ;  (5)  the  percen- 
tage of  waste  from  mains  and  fittings. 

The  total  quantity  of  water    supplied  for 
all  purposes  will  vary  from  about  20  gallons 
per  head  per  day  in  residential  towns  up  to 
30  or  35  gallons  per  head  in  manufacturing 
towns,  and  in  exceptional  cases  even  the  latter 
figure  may  be  exceeded.     The  actual  quantity 
supplied  day  by  day  will  also  vary  according 
to  the  season  of  the  year,  whether  summer 
or  winter,  whether  wet   or  dry.      The  con- 
sumption   is    usually   greater    during    frosty 
weather,   owing    to  waste   from   burst  pipes 
and   mains,    also    to    householders    allowing 
their  taps  to   "run"  during  the  night  with 
the  view  of  preventing  the  water  freezing  in 
the  pipes.     The  actual  flow  through  the  town 
mains    will    also   vary   considerably    during 
different  hours  of  the  day.     The  maximum 
draught  on  the  distribution  mains  may  occur 
at  any  time  between  the  hours  of  8  A.M.  and 
5  P.M.,  and  is  frequently  at  its  highest  between 
the  hours  of  9  A.M.  and  noon.      The  mains 
must,  of  course,  be  capable  of  passing  water 
at  the  maximum  rate  without  undue  loss  of 
"  head  "  or  pressure.      As  an  approximation, 
the  maximum  rate  of  draught  may  be  taken 
at  twice  the  average  consumption  in  the  24 
hours.     In  regard  to  the  rate  of  flow  in  the 
water  mains,  a  well-established  empirical  rule 
fixing  the  velocity  at  3  ft.  per  second  has  been 
laid  down  as  suitable  for  fairly  large  mains. 

CHARACTER  OF  WATER  FROM  DIFFERENT 
SOURCES  AND  CAUSES  OF  IMPURITY. — Water, 
though  pure  at  its  source,  may  receive  impuri- 
ties in  a  variety  of  ways  before  it  reaches 
the  consumer.  As  met  with  in  nature  it  owes 
its  characteristics  largely  to  the  geological 


526 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


WAT 


strata  or  other  physical  conditions  with  which 
it  has  come  into  contact.  Water  derived 
from  the  older  formations,  as  igneous  rocks, 
granite,  or  millstone  grit,  is  usually  very  pure, 
contains  only  a  small  quantity  of  minerals  in 
solution,  and  a  very  insignificant  amount  of 
organic  matter.  Waters  from  limestone  and 
dolomite  are  clear  and  bright  in  appearance, 
but  contain  sulphates  of  calcium  and  magne- 
sium in  large  quantities,  and  consequently 
have  a  high  degree  of  permanent  hardness. 
These  waters  are  not  good  for  manufacturing 
purposes  and  should  not  be  used  for  domestic 
supply  if  a  softer  water  can  be  obtained. 

A  considerable  number  of  towns  in  the 
Midlands  and  North  of  England  are  supplied 
from  wells  sunk  in  the  New  Red  Sandstone 
formation,  which  yields  a  large  quantity  of 
water,  usually  of  a  good  class  well  suited  for 
public  supplies.  The  towns  of  Birkenhead, 
Nottingham,  Wolverhampton,  St.  Helens,  and 
many  others  draw  supplies  from  this  strata. 
Birmingham  and  Liverpool  have  also  in  the 
past  taken  large  quantities  from  the  same 
source.  The  water  at  Nottingham  and  Wolver- 
hampton is  between  8°  and  10°  of  hardness, 
whilst  at  St.  Helens  it  is  23°  before  the 
softening  treatment  and  10°  after.  Bristol 
is  supplied  from  springs  in  the  limestone 
conglomerate,  and  deep  wells  in  the  new  red 
sandstone,  and  the  water  has  a  hardness  of 
about  18°. 

The  chalk  is  one  of  the  most  important  of 
water-bearing  strata  and  yields  water  of  excel- 
lent and  wholesome  quality.  It  is  always 
sparkling  and  agreeable  to  the  palate  on 
account  of  the  large  quantity  of  carbonic  acid 
in  solution  ;  it  contains  calcic  carbonate,  often 
in  large  quantities,  and  is  therefore  hard,  but 
softens  considerably  upon  boiling.  A  large 
number  of  towns  in  the  south  and  east  of 
England  are  supplied  from  this  source,  as 
well  as  a  considerable  part  of  London.  The 
hardness  may  amount  to  16°  or  18°,  whilst 
that  from  the  lower  greensand,  below  the 
chalk,  is  frequently  much  less,  the  "  Mid- 
Kent  "  supply  from  this  source  being  about 
10°. 


Traces  of  iron  are  to  be  found  in  practically 
all  waters,  and  it  is  often  met  with  in  natural 
spring  or  deep  well  waters  to  an  extent  suffi- 
cient to  render  the  water  unfit  for  use  and 
of  a  very  disagreeable  taste.  This  is  frequently 
the  case  with  water  derived  from  sandstones, 
such,  for  example,  as  the  Ashdown  sands,  or 
any  strata  largely  impregnated  with  iron. 
The  small  quantity  of  one-fifth  of  a  grain  per 
gallon  of  water  will  impart  an  unpleasant 
chalybeate  taste  to  the  water.  Iron  is  remov- 
able by  precipitation  with  lime  and  oxidation. 
It  may  frequently  be  removed  from  deep  well 
waters  by  thorough  aeration,  time  being 
allowed  for  precipitation.  It  is,  however, 
much  more  expeditiously  and  conveniently 
removed  by  a  system  of  forced  aeration  under 
pressure  in  mechanical  filters,  the  suspended 
oxide  being  afterwards  filtered  out  (see 
"MECHANICAL  FILTRATION"). 

Surface  and  subsoil  waters  present  many 
variations  in  composition  according  to  the 
nature  of  the  ground  where  they  are  collected. 
The  surface  water  from  the  millstone  grit, 
Silurian  and  Devonian  formations,  from 
heaths,  moorlands,  and  uncultivated  lands,  is 
usually  pure,  but  if  the  catchment  area  con- 
tains much  peat  it  will  be  of  a  brownish 
colour  and  occasionally  acid  in  reaction. 
From  cultivated  and  manured  lands  consider- 
able quantities  of  organic  matter  may  be 
found  in  solution,  and  even  in  the  absence  of 
organic  matter  nitrates,  nitrites,  chlorides, 
and  phosphates  are  sure  to  be  present,  indi- 
cating some  previous  contamination  with 
animal  matter. 

The  water  from  graveyards  and  marshes 
must  always  be  regarded  as  dangerous  sup- 
plies ;  they  contain  organic  matter  in  suspen- 
sion or  solution  in  addition  to  nitrates  and 
nitrites.  Rain  water,  although  a  useful  source 
in  rural  districts  if  properly  collected,  cannot 
be  utilised  in  towns  owing  to  the  many 
impurities  taken  up  from  the  atmosphere  and 
the  roofs  of  houses. 

Other  means  of  contamination  of  water 
supplies  may  occur  from  the  washing  of  large 
quantities  of  debris  and  decaying  vegetable 


527 


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ENCYCLOPAEDIA  OF 


WAT 


matter  into  open  water  conduits.  If  the 
water  is  collected  from  land  dotted  over  with 
dwellings,  farmsteads,  agricultural  buildings, 
&c.,  sewage  may  find  its  way  into  the  water 
conduit,  springs,  or  wells,  and  if  such  sewage 
contamination  carry  the  specific  poison  of  any 
disease,  such  as  typhoid  or  cholera,  it  may 
thus  speedily  contaminate  large  quantities  of 
water,  including  the  rivers  or  streams  into 
which  it  ultimately  flows. 

Trade  refuse,  such  as  the  effluents  from  a 
dye  works,  gas,  brick,  or  chemical  works, 
would  seriously  pollute  a  water  supply  if 
allowed  to  percolate  into  a  porous  strata  and 
thus  reach  the  well,  conduit,  or  stream  from  or 


FIG.  2. 

by  which  water  is  derived  or  conveyed.  In 
rural  districts  the  fouling  of  water  chiefly 
arises  from  the  proximity  of  dwellings,  cess- 
pools, stables,  or  pig-styes  to  the  well  or  other 
source  of  supply.  Fig.  2  illustrates  how 
impurities  may  readily  reach  a  well  sunk  in  a 
porous  strata.  If  in  such  a  case  there  had 
been  an  impermeable  bed  of  clay  (A  B)  over- 
lying the  rock,  and  the  well  properly  lined 
with  iron  tubes  or  brickwork  from  the  ground 
surface  to  the  rock  in  such  a  way  as  to  com- 
pletely exclude  the  top  waters,  a  good  and 
pure  supply  might  have  been  obtainable  from 
the  rock  below  if  of  a  porous  and  permeable 
nature. 

PHYSICAL  CHARACTERISTICS  OF  GOOD  DRINKING 
WATER. — It  will  be  convenient  here  to  briefly 
summarise  a  few  of  the  leading  physical 
characteristics  of  a  good  drinking  water.  It 
must  be  clear  and  entirely  free  from  sediment 
or  suspended  matter.  Ordinary  printed  matter 
should  be  clearly  read  through  at  least  18  in. 


depth  of  water.  It  should  be  colourless  or 
bluish  if  looked  at  through  a  depth  of  2  or 
3  ft.,  and  should  be  bright  and  sparkling 
showing  that  it  is  well  charged  with  air  and 
carbonic  acid.  The  water  should  have  the 
pleasant  sparkling  taste  of  good  water,  and  be 
free  from  brackish  or  other  unpleasant  or 
peculiar  taste.  There  must  be  no  smell  other 
than  the  peculiar  indescribable  smell  which 
fresh  spring-water  yields.  It  should  be  soft 
to  the  touch  and  dissolve  soap  easily. 

Hardness  of  water  is  that  property  which 
causes  it  to  decompose  a  certain  quantity  of 
soap  before  a  lather  can  be  formed.  It  is 
usually  expressed  in  degrees  upon  what  is 
known  as  Clarke's  scale,  in  which  one  degree 
of  hardness  implies  one  grain  of  bicarbonate 
or  sulphate  of  lime  in  each  gallon  of  water. 

Water  at  and  below  about  6°  of  hard- 
ness is  considered  "soft"  water,  and  above 
this  range  it  would  be  styled  "  hard." 

Hardness  is  of  two  kinds — (1)  temporary  or 
removable  hardness,  (2)  permanent  or  irre- 
movable. 

Temporary  hardness  depends  upon  the 
presence  of  calcic  and  magnesic  carbonates 
held  in  solution  by  carbonic  acid  (COs),  with 
which  it  is  loosely  combined.  When  the  C02 
is  drawn  off,  as  it  can  be  by  boiling,  the 
carbonates  are  precipitated  and  form  a  white 
deposit,  giving  rise  to  the  "fur"  found  lining 
the  interior  of  kettles  and  boilers. 

Another  method  of  precipitating  the  car- 
bonates is  the  addition  of  such  an  amount  of 
lime-water  as  will  combine  with  all  the  C02  in 
solution,  and  so  throw  down  both  the  car- 
bonates originally  contained  in  the  water,  and 
those  formed  by  the  union  of  the  C02  and  the 
added  lime-water. 

Permanent  hardness  is  due  to  the  presence 
of  the  sulphates  of  calcium  and  magnesium, 
and  chlorides ;  also,  in  a  minor  degree,  to  iron, 
alumina,  and  free  acid.  Hardness  of  this 
kind  cannot  be  removed  by  boiling 

One  grain  of  chalk  (calcic  carbonate)  wastes 
8  grains  of  soap,  so  that  the  total  annual 
waste  of  soap  for  any  given  population  using 
water  of  known  hardness  may  be  readily 


528 


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MUNICIPAL   AND    SANITARY  ENGINEERING. 


WAT 


calculated.  In  this  way  it  has  been  estimated 
that  the  City  of  Glasgow  saved  something  like 
£36,000  annually  in  soap  by  the  introduction 
of  the  very  soft  water  from  Loch  Katrine  in 
the  place  of  its  former  harder  supply.  The 
hardness  of  the  water  supplied  to  various 
towns  differs  very  widely.  The  Glasgow 
(Loch  Katrine)  water  is  under  one  degree  of 
hardness,  that  supplied  to  London  about  16°, 
and  that  of  the  small  town  of  Wellingborough 
(Northants)  as  much  as  45°  hardness.  The 
water  here  is  softened  by  Atkin's  process. 

THE  SOFTENING  PEOCESS  by  the  addition  of 
lime  water  indicated  above  was  introduced  by 
Dr.  T.  Clarke  of  Aberdeen  in  1841 ;  upon  this 
principle  the  more  recent  methods  are  based. 
Among  the  towns  using  softening  processes 
for  their  supplies  may  be  mentioned  South- 
ampton, St.  Helens,  Stroud,  Wellingborough, 
Saffron  Walden,  and  others.  The  cost  of 
softening  varies  from  \d.  to  frf.  per  1,000 
gallons,  and  from  10°  to  24°  of  hard- 
ness are  removed.  In  the  modified  process 
known  as  the  Porter-Clark  method  the  lime 
is  mixed  with  watar  by  paddles  and  is  then 
passed  through  filter  presses  of  cloth,  insuring 
a  clear  product  and  saving  time  and  space. 
This  process  is  specially  adapted  for  waters  of 
a  high  temporary  hardness  like  those  of 
London  from  the  chalk.  The  following  forma- 
tions as  a  rule  yield  hard  waters — Chalk,  Upper 
Greensand,  Oolites,  Lias,  Mountain  Limestone, 
Coal  Measures,  and  Devonian.  Soft  waters 
are  obtained  from  the  Bagshot  Beds,  Lower 
Greensand,  Silurian,  Metamorphic,and  Igneous 
rocks. 

ACTION  OF  WATER  UPON  LEAD. — The  ill- 
effects  of  the  action  of  some  waters  upon  lead 
are  now  well  known,  and  great  trouble  has 
resulted  from  this  cause  in  connection  with 
many  water  supplies,  especially  in  the  North 
of  England.  Lead  possesses  a  cumulative 
poisonous  action  by  which  small  quantities 
accumulate  through  the  daily  use  of  waters 
so  tainted,  until  serious  illness  ultimately 
ensues.  A  blue  line  around  the  gums  is  an 
important  characteristic  symptom  of  lead 
colic  or  "  plumbism  "  as  it  is  called.  It  is 

M.S.E.  529 


very  seldom  that  water  in  its  natural  state  is 
tainted  with  lead,  but  it  becomes  so  polluted  in 
the  course  of  distribution  by  contact  with  lead 
pipes,  cisterns,  &c.  The  soft  moorland  water 
of  the  Vartry  attacked  lead  so  readily  that  tin- 
lined  pipes  were  used  when  the  new  supply 
was  introduced  in  Dublin. 

At    Sheffield,  too,  a    similar   difficulty  was 
experienced  with  a  part  of  the  supply  where 
the  water  was  peaty  and  of  an  acid  character. 
The   soft  waters  of  Loch  Katrine,  however, 
gave   little  or  no  trouble  in    Glasgow.     The 
waters  which  act  most  on  lead  are :    (1)  The 
purest  and  most  highly  oxygenated,  such  as 
rain-water,  and  the  moorland  waters  of  up- 
land streams  ;  (2)   Those  containing  organic 
matter,  nitrates,  nitrites,  and  chlorides,  such  as 
water  contaminated  with  sewage  ;    (3)  Waters 
containing  a  free  acid,  soft  peaty  waters  as 
supplied    to   many   towns   in   the    North    of 
England.      Among   those   waters   which   act 
least   upon  lead  are,  hard  waters  containing 
carbonates,  phosphates,  and  -  sulphates,  espe- 
cially carbonate  of  lime.     Such  waters  soon 
deposit  a  protective  coating  on  the  lead  sur- 
faces.    There  are  many  other  circumstances 
influencing  the  action  of  water  on  lead  pipes. 
(1)  It  is  affected  by  the  length  of  time  water  is 
left  to  stand  in  the  service  pipes  ;    (2)  By  the 
temperature  of  the  water   and  the   pressure 
under  which  it  exists  in  the  pipes,  an  increase 
of  either  favours  the  solution  of  the  metal ;  (3) 
New  lead  piping  is  more  easily  dissolved  than 
that  which  has  been  in  use  for  any  length  of 
time ;   (4)  The  lead  is  more  readily  acted  on  if 
other  metals,  as  iron,  zinc,  or  tin,  are  in  con- 
tact therewith,  as  galvanic  action  may  be  set 
up ;   (5)    Bending   a   pipe   against   the  grain 
and  so  exposing   the  structure  of   the  metal 
increases  the  risk  of  solution ;  (6)  Zinc  pipes, 
into  the  composition  of  which  lead  often  enters, 
yield   lead   in  large  quantities  to  the  water. 
Water  which  has  been   standing   in   a   lead 
service  for  a  considerable  time  should  be  first 
drawn  off  before  taking  a  supply  for  drinking 
purposes,  should   there  be  any  danger  from 
lead-poisoning.      Filtration     of     the     water 
through   animal  charcoal  is  a  good  plan  to 

M  M 


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ENCYCLOPAEDIA   OF 


WAT 


insure  freedom  from  lead.  The  charcoal, 
however,  will  require  to  be  regularly  renewed. 
New  and  bright  lead  is  at  first  acted  on  by 
most  waters  until  a  protective  coating  has 
been  formed  on  the  surface.  In  cleaning  out 
a  cistern  this  coating  should  not  be  removed, 
neither  should  cleansing  with  acids  be  resorted 
to.  The  best  material  for  a  water  cistern  is 
slate.  Both  zinc  and  galvanised  iron  are 
affected,  especially  the  former.  The  lead  from 
the  paint  of  internally  painted  cisterns  is 
sometimes  dissolved  by  the  water.  Portland 
cement  makes  a  good  surface,  but  is  not  a 
convenient  material  to  use  for  household  pur- 
poses. To  detect  lead  in  water  a  test  may  be 
made  by  putting  one  drop  of  sulphide  of 
ammonium  in  a  wine-glass  full  of  water  and 
stirring  with  a  glass  rod.  The  water  will 
immediately  discolour  (black)  if  lead  is 
present.  In  a  valuable  report  by  Dr.  Houston 
on  "  Moorland  waters  in  regard  to  their  action 
on  lead,"  submitted  to  the  Local  Government 
Board,  and  published  in  1903,  the  whole 
question  has  received  very  exhaustive  treat- 
ment. It  is  of  great  public  importance  having 
regard  to  the  large  proportion  of  the  popula- 
tion of  this  country  receiving  water  supplies 
from  upland  gathering  grounds  liable  to 
yield  waters  of  plumbo-solvent  or  erosive 
tendencies. 

THE  CONSTRUCTION  OF  WATERWORKS.  - 
SYSTEMS  OF  SUPPLY. — The  system  of  works 
upon  which  towns  are  supplied  with  water  are 
usually  classified  either  as  "  gravitation " 
works  or  "pumping"  works;  not  infrequently 
it  may  be  a  combination  or  modification  of 
both.  In  a  gravitation  supply,  the  water  is 
usually  obtained  from  a  surface  gathering 
ground,  or  catchment  area,  situate  a  consider- 
able distance  from  the  town  to  be  supplied, 
and  at  such  an  elevation  as  will  admit  of  the 
water  derived  therefrom  being  collected  in  an 
impounding  or  storage  reservoir  from  which 
it  may  gravitate  through  perhaps  several 
miles  of  pipe-line  or  aqueduct  to  a  service 
reservoir  situated  near  the  town.  The  latter 
reservoir  must  also,  in  turn,  be  at  such  an 
altitude  as  will  insure  the  supply  being 


delivered  to  the  tops  of  all  the  various  build- 
ings within  the  area  of  supply  after  having 
made  satisfactory  allowance  for  frictional 
losses  of  head  in  the  distributing  mains  during 
times  of  heaviest  draught.  The  general 
arrangement  of  such  a  system  is  showi 
diagrammatically  in  Fig.  3,  in  which  tl 
section  from  A  to  E  illustrates  the  supj 
collected  from  the  gathering  ground  .1,  ii 
a  storage  reservoir  B,  passing,  if  necesss 
through  the  filter  beds  and  clear  water  tani 
below,  and  then  gravitating  through  a  pipe- 
line or  aqueduct  to  the  service  reservoirs  D, 
which  are  at  a  sufficient  elevation  to  supply 
the  town  situated  at  E.  It  frequently 
happens,  however,  that  small  outlying  parts 
of  a  water  area  may  rise  to  a  height  above  the 
top  water  line  of  the  service  reservoirs,  and  in 
such  case  the  water  for  these  limited  districts 
must  be  pumped  through  this  additional 
height,  usually  over  a  "  stand-pipe  "  or  into 
an  elevated  water-tank  or  tower  situated  upon 
the  highest  ground  available,  so  as  to  com- 
mand the  tops  of  the  highest  houses  within 
this  area.  In  gravitation  supplies,  the  works 
involved  usually  consist  of  any  necessary 
preparation  of  the  gathering  ground  such  as 
the  removal  of  dwellings,  farmsteads,  &c., 
where  they  may  be  likely  to  cause  pollution, 
the  formation  of  impounding  or  storage 
reservoirs  in  the  lowest  suitable  part  of  the 
catchment  area  by  the  building  of  large 
earthen  or  masonry  dams  across  the  valley, 
the  diversion  into  the  main  watershed  of 
water  from  adjoining  areas  by  means  of  pipe- 
lines or  tunnels,  the  construction  of  the  main 
aqueduct  from  the  storage  reservoir  to  the 
service  reservoirs  which  should  be  placed  near 
the  town,  and  numerous  accessory  works 
incidental  to  the  foregoing.  The  North  and 
West  of  England  and  the  country  of  Wales 
have  excellent  gathering  grounds  situate  at 
high  altitudes  and  subject  to  great  rainfall. 
A  great  many  towns  in  these  parts  have 
therefore  naturally  availed  themselves  of  this 
excellent  means  of  supply.  Glasgow  receives 
its  supply  from  Lochs  Katrine  and  Arklet, 
Manchester  from  Lake  Thirlmere,  Liverpool 


530 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


WAT 


from  Lake  Vyrnwy  (North  Wales),  Bradford 
from  Nidd  Valley,  and  Birmingham  from  the 
Elan  Valley  in  Mid-Wales.  In  the  east  and 
south-east  of  England  such  gathering  grounds 
are  not  available,  and  the  supplies  are  derived 
either  from  rivers,  springs,  or  deep  wells, 
sources  which  are,  as  a  rule,  at  a  low  level 
with  respect  to  the  district  to  be  supplied,  and 
the  waterworks  therefore  necessarily  becomes 
a  "pumping  scheme." 

Referring  again  to  Fig.  3  it  will  be  seen 
that  if  the  ground  rises  from  the  point  F  in 
the  section  instead  of  descending,  as  in  the 
gravitation  section  A  to  E,  pumping  will  be 
necessary  to  raise  the  water  the  required 
"  lift  "  through  lines  of  rising  main  into  high 


but,  on  the  other  hand,  against  this  is  to  be 
set  the  permanent  annual  expenditure  of  a 
pumping  works.  So  that  in  cases  where  an 
ample  supply  of  equal  purity  upon  either 
system  may  be  secured  the  question  of  cost 
will  usually  be  the  deciding  factor. 

The  water  supply  of  the  Metropolis  affords 
the  largest  example  in  the  world  of  systems  of 
pumping  works,  the  water  being  derived  from 
the  Thames  and  Lea  and  deep  wells  in  the 
chalk. 

CATCHMENT  AREAS  AND  STORAGE.  —  The 
extent  of  catchment  area  and  storage  capacity 
required  for  the  supply  of  a  town  will  depend 
mainly  upon  the  quantity  of  water  required 
dailv,  the  amount  of  the  annual  rainfall  and 


K CoUecticn 


— Pmnping  and-  Distrttmtum,  - 


_  I 


PUMPING 
SCHEME 


Tqwn, 
iE    GRAVITATION 

SCHEME 
\ 


FIG.  3.  —  Diagram  Illustrating  Principle  of  Gravitation  and  Pumping  Schemes. 


service  reservoirs  to  supply  the  town  at  H. 
Other  parts  of  the  system  such  as  storage 
reservoirs,  niters,  and  clear  water  tanks  may 
remain  the  same  in  either  case. 

In  a  pumping  scheme  there  is  usually  less 
of  what  may  be  called  heavy  engineering  work 
involved  in  the  collection,  storage,  and  con- 
veyance of  the  water,  but  a  large  outlay  is 
necessary  in  the  provision  of  pumping 
machinery  and  buildings.  The  question  of 
choice  between  gravitation  and  pumping 
schemes  of  supply  often  arises  in  practice.  It 
will  be  obvious  that  no  general  statement  of 
preference  for  one  or  the  other  could  be  made, 
as  their  relative  merits  will  depend  upon  local 
conditions  and  the  capital  and  working  costs 
of  each  scheme.  Generally  speaking,  the 
initial  cost  of  a  gravitation  supply  is  greatest, 


evaporation  over  that  area,  and  the  physical 
nature  of  the  ground  surfaces.  It  will  be 
obvious  that  a  much  larger  proportion  of  the 
total  rainfall  may  be  collected  from  a  rocky 
and  precipitous  area  than  from  one  of  a  less 
hilly  description  or  where  a  large  amount  of 
percolation  may  take  place.  Generally  speak- 
ing, it  has  been  found  in  England  that  the 
supply  which  can  be  relied  upon  from  any 
definite  gathering  ground  may  be  calculated 
by  the  formula  : — 

-R-E 
o 

where,  Q  =  the  daily  supply  in  gallons. 
A  =  catchment  area  in  acres. 
R  =  average  annual  rainfall  in  inches. 
E  =  loss  of  rainfall  by  evaporation  in 
inches. 


531 


M  M  (2 


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ENCYCLOPEDIA  OF 


WAT 


In  England,  the  loss  by  evaporation  amounts 
to  from  10  to  18  in.  in  the  year  according 
to  circumstances.  Where  no  natural  lake  is 
available,  as  in  the  case  of  the  Glasgow  supply 
from  Loch  Katrine  or  the  Manchester  supply 
from  Thirlmere,  the  water  flowing  from  a 
gathering  ground  is  stored  up  in  the  rainy 
season  for  use  during  the  dry  period,  by  forming 
an  artificial  lake  or  reservoir.  This  is  done  by 
constructing  a  masonry  or  earthen  dam  across 
the  lower  part  of  the  valley  of  a  mountain  water- 
course. In  providing  such  storage  it  is  found 
to  be  unnecessary  to  thus  attempt  to  equalise 
supply  over  a  longer  period  than  a  consecutive 
three  dry  years'  term,  as  by  so  doing  there 
would  be  many  years  when  the  reservoirs 
would  not  get  filled.  The  storage  will  also  be 
regulated  by  the  number  of  consecutive  days 
in  a  dry  time  during  which  the  supply  might 
have  to  be  drawn  from  the  reservoir  without 
any  addition  thereto.  This  period  varies  con- 
siderably in  different  districts,  and  depends 
upon  the  fluctuations  of  rainfall,  the  usual 
length  of  periods  of  drought,  the  amounts  of 
percolation  and  evaporation,  and  other  con- 
ditions, so  that  a  much  smaller  storage  would 
suffice  in  a  wet  district  than  in  a  dry  one. 
For  these  reasons  the  storage  provided  may 
vary  from  about  70  to  as  much  as  300  days' 
supply,  but  in  England  will  mostly  lie  between 
a  minimum  of  100  days  in  wet  districts  and  a 
maximum  of  250  days  in  very  dry  districts. 

COMPENSATION  WATER. — In  addition  to  the 
water  obtained  from  a  catchment  area  and 
stored  in  reservoirs,  it  is  necessary  to  consider 
the  question  of  compensation,  payable  only  in 
water,  to  parties  lower  down  the  streams 
affected,  in  consideration  of  the  flood  water 
abstracted  for  purposes  of  supply  to  some 
distant  town.  To  insure  that  the  flow  of  the 
streams  shall  never  be  less  than  a  certain 
stipulated  amount,  the  daily  flow  of  "compen- 
sation water  "  is  fixed  by  the  Act  of  Parliament 
authorising  the  construction  of  the  works.  It 
is  clear  that  damage  may  result  from  such 
abstraction  of  water  from  streams,  but,  on  the 
other  hand,  it  is  also  equally  certain  that  con- 
siderable benefit  must  accrue  to  riparian 


owners  from  the  construction  of  impounding 
reservoirs  mitigating  the  damaging  effects  of 
floods  and  equalising  the  flow  of  the  streams 
throughout  the  year. 

In  practice,  where  the  entire  catchment  are 
of  a  stream  has  been  appropriated  for  tl 
supply  of  an  impounding  reservoir,  the  amount 
of  compensation  water  has  been  fixed  at  one- 
third  of  the  average  yield  of  the  gathering 
ground  in  question.  Formerly  the  proportion 
of  an  ordinary  stream  available  for  useful 
purposes  appears  to  have  been  much  over- 
estimated, and  the  conditions  imposed  in 
regard  to  compensation  water  were  more 
onerous  than  are  now  proved  to  be  necessary. 
Thus,  in  1847,  Liverpool  was  required  to 
deliver  one-half  of  the  available  yield  from 
the  Eivington  watershed  as  compensation, 
and  Manchester,  in  1848,  delivered  two-fifths 
of  the  yield  from  the  Longdendale  area  into 
the  river  Etherow.  These  have  since  both 
been  reduced  to  about  one-third  of  the  avail- 
able yield.  The  compensation  water  delivered 
by  the  Liverpool  Corporation  into  the  river 
"Vyrnwy  (Act,  1880)  amounts  to  only  about 
one-fourth  of  the  yield  of  the  catchment  area, 
whilst  that  from  the  Thirlmere  Works  (Act, 
1879)  is  only  about  one-tenth  of  the  available 
annual  yield  of  the  gathering  ground. 

LEADING  FEATURES  OF  SOME  LARGE  GRAVI- 
TATION SUPPLIES.  —  Manchester,  in  appro- 
priating Lake  Thirlmere  for  the  purposes  of 
supply,  took  powers  to  raise  its  natural  level 
50  ft.,  by  building  a  concrete  dam,  faced  with 
masonry,  across  its  outlet,  from  the  solid  rock 
below  up  to  a  height  of  57  ft.  above  the  former 
level  of  the  lake.  By  this  means  the  area  of 
the  lake  was  increased  from  328|  acres  to  793 
acres,  and  a  total  volume  of  about  8,131 
million  gallons  of  water  was  impounded  at  a 
low  cost.  The  storage  is  equal  to  a  quantity 
of  32'6  in.  over  the  whole  catchment  area, 
and  is  able  to  afford  a  supply  of  50  million 
gallons  a  day  for  a  period  of  160  days.  It  is 
important,  in  this  case,  to  have  ample  storage, 
as  the  total  catchment  area  only  amounts  to 
11,000  acres,  or  about  220  acres  per  million 
gallons  daily  supply.  The  rainfall,  however, 


532 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


WAT 


in  this  district  is  large,  amounting  on  the 
average  of  18  years'  gaugings  to  85  in. ; 
whilst  the  fall  for  three  consecutive  dry  years 
is  as  much  as  71  in.  Owing  to  the  steep 
rocky  nature  of  the  hill  slopes  the  proportion 
of  the  rainfall  reaching  the  lake  is  also  large. 
The  compensation  water  to  be  discharged 
amounts  to  5^  million  gallons  a  day.  An 
aqueduct  about  96  miles  in  length,  and  7  ft. 
1  in.  wide  by  7  ft.  high  where  in  tunnel,  with 
pipe-lines  where  the  invert  falls  below  the 
hydraulic  grade  line,  conveys  the  supply  to 
the  Prestwich  reservoir,  Manchester. 

Liverpool  had  not  the  advantages  of  a 
natural  lake  at  Vyrnwy,  but  by  the  con- 
struction of  a  concrete  and  masonry  dam 
about  85  ft.  high,  above  the  river  bed,  across 
that  river,  impounded  a  storage  of  13,000 
million  gallons  for  the  supply  of  that  city  with 
a  total  daily  quantity  of  40  million  gallons.  A 
compensation  water  of  13J  million  gallons  a 
day,  or  one-third  of  the  supply,  was  also  pro- 
vided. This  was  more  than  five  times  the 
dry  weather  flow  of  the  rivers.  The  reservoir 
affords  sufficient  storage  for  about  220  days. 
The  catchment  area  is  23,500  acres,  or  588 
acres  per  million  gallons  daily  supply.  The 
mean  yearly  rainfall  for  a  term  of  20  years 
from  a  large  number  of  gauges  was  found  to  be 
65*16  in.,  and  the  average  fall  of  three  dry 
years  (1887-89)  amounted  to  54*58  in.  The 
supply  is  conveyed  to  Liverpool  by  means  of 
an  aqueduct,  7  ft.  in  diameter  in  the  tunnels 
and  about  68J  miles  in  length,  discharging 
into  the  service  reservoirs  at  Prescot. 

Bradford. —  The  new  Nidd  Valley  works  for 
Bradford  provide  an  additional  supply  of 
20  million  gallons  a  day  for  that  city,  by 
impounding  on  the  Upper  Nidd  a  quantity  of 
2,596  million  gallons  from  a  catchment  area 
of  18,200  acres.  This  gives  a  catchment  area 
of  910  acres  per  million  gallons  daily  supply. 
There  is  also  a  further  gathering  ground  of 
9,900  acres  for  compensation  purposes.  The 
rainfall,  based  on  a  12  years'  average,  is 
48  in.  The  dam  forming  the  Gouthwaite 
compensation  reservoir  is  of  cyclopean  rubble 
masonry  in  cement,  and  has  a  maximum  depth 


from  top  water  level  to  the  foundations  of 
105  ft.  Its  thickness  at  the  base  is  70  ft. 
The  water  is  conveyed  from  the  Nidd  Valley 
to  the  Chellow  Heights  service  reservoir,  a 
distance  of  32  miles,  in  an  aqueduct  5  ft.  6  in. 
wide  by  6  ft.  3  in.  high,  with  pipes  across  the 
valleys  below  the  hydraulic  grade  line. 

Birmingham. — One  of  the  largest  schemes 
of  late  years  is  that  for  the  supply  of 
Birmingham  from  the  Elan  Valley,  in  Mid- 
Wales.  Here  six  large  reservoirs  are  contem- 
plated, having  an  aggregate  storage  capacity 
of  18,000  million  gallons,  capable  of  giving, 
for  a  period  of  180  days,  a  supply  of  75 
million  gallons  a  day  to  Birmingham,  and  a 
compensation  water  of  27  million  gallons  a 
day,  or  rather  more  than  a  third  of  the  supply. 
The  catchment  area  is  45,560  acres,  or  608 
acres  per  million  gallons  daily  supply,  and 
the  average  rainfall  over  a  long  term  is  about 
70  in.  The  mean  of  three  dry  years  is 
56  in.  The  dams  are  of  masonry  and  vary 
in  height  from  98  ft.  to  122_ft.  above  the  river 
bed.  The  aqueduct  is  74  miles  long  and 
delivers  into  the  Frankley  reservoir,  to  the 
west  of  Birmingham. 

RESERVOIR  DAMS  for  impounding  storage 
water  are  constructed  of  masonry,  concrete, 
or  earth,  and  are  dealt  with  under  article 
"  DAMS,  EARTHEN  AND  MASONRY." 

WASTE  WEIR,  BYE-CHANNEL,  AND  RESIDUUM 
LODGES. — The  respective  positions  and  func- 
tions of  waste  weirs,  bye-channels,  and 
residuum  lodges  are  illustrated  in  the 
accompanying  Fig.  4.  A  waste  weir  forms 
a  very  important  accessory  to  every  reservoir, 
and  should  be  provided  at  a  suitable  place  at 
the  side  of  the  reservoir.  The  sill  of  the  weir 
should  be  at  a  slightly  lower  level  than  the 
highest  proposed  water  level  in  the  reservoir, 
so  that  any  surplus  water  discharging  into  a 
full  reservoir  in  flood  time  may  escape  over 
the  weir  and  away  through  the  waste  water 
course  to  the  natural  stream  below. 

The  length  of  weir  required  in  any  given 
case  will  depend  upon  what  depth  of  water  it 
may  be  considered  safe  to  pass  over  it,  which 
should  ordinarily  not  exceed  from  1  ft.  to 


533 


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18  in.,  otherwise  the  safety  of  the  embank- 
ment may  be  endangered.  The  weir  should 
therefore  be  made  long  enough  to  dis- 
charge the  full  quantity  of  flood  water 
which  the  catchment  area  is  calculated  to 
send  down,  so  that  this  influx  may  be  readily 
conveyed  away  down  the  waste  water  course 
without  raising  the  top  water  level  of  the 
reservoir  above  the  limit  proposed  in  the 
design  of  the  embankment  or  dam.  The  length 
of  weir  in  practice  is  very  generally  made 
from  2£  ft.  to  4  ft.  per  100  acres  of  drainage 
area,  varying  according  to  the  locality  and 


VSTREAM 

RESIDUUM 
' LODGE 


of  flat  steps,  not  exceeding  1  ft.  rise  with 
3  ft.  tread,  into  the  upper  part  of  the  waste 
water  course. 

THE  WASTE  WATER  COURSE  is  designed  to 
carry  all  the  water  flowing  over  the  weir  or 
coming  down  the  bye-channel  safely  into  the 
natural  stream  below.  It  therefore  has  a 
fall  equal  to  the  greatest  depth  of  water  in  the 
reservoir,  and,  as  the  shortest  route  is  usually 
selected  for  reasons  of  economy,  its  inclination 
frequently  becomes  very  considerable.  The 
waste  water,  therefore,  must  not  flow  down  at 
such  a  velocity  as  will  injure  the  stability  of 

WASTE  WEIR 

A/AL.VE  HOUSE 


. STREAM 


FIG.  4. — Plan  of  Reservoir,  showing  Waste  Weir,  Bye-Channels,  and  Residuum  Lodges. 


rainfall  of  the  district.  In  the  case  of  an 
earthen  embankment  the  waste  weir  should 
be  formed  in  the  solid  ground  at  one  of  the 
extremities  of  the  dam  and  not  passed  over 
any  of  the  made  earthwork  of  the  bank.  If 
the  configuration  of  the  ground  is  favourable 
the  weir  may  sometimes  be  formed,  with 
slight  cutting,  through  some  depression  at  the 
side  of  the  reservoir  and  the  flood  waters  thus 
removed  as  far  as  possible  from  the  made 
bank. 

In  order  to  secure  the  greatest  length  of 
weir,  and  to  reduce  the  amount  of  cutting, 
the  weir  is  often  formed  curved  in  plan — the 
water,  after  passing  over,  falling  by  a  series 


the  work,  although  on  grounds  of  safety  and 
economy  it  is  desirable  to  discharge  it  as 
quickly  as  possible.  To  check  the  velocity  of 
flow  a  good  plan  is  to  form  the  waste  water 
channel  in  a  series  of  long  shallow  steps  so 
constructed  as  to  retain  a  pool  of  water  on  the 
top  of  each  step,  thus  resembling  a  series  of 
small  weirs  separated  by  pools,  which  have 
the  effect  of  breaking  up  the  impact  of  the 
falling  stream.  The  steps  shown  in  Figs.  5 
and  6  are  curved  in  plan  with  the  view  of 
increasing  the  stability  of  the  work  and  the 
discharging  power. 

In  the  case  of  masonry  dams  the  waste 
flow   over   a   portion   of    the   dam   itself 


534 


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MUNICIPAL   AND   SANITAEY   ENGINEERING. 


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terminating  its  crest  at  the  top  water  level. 
The  Vyrmvy  dam  is  a  good  instance  of  this 
form  of  waste  weir,  and  for  this  purpose 
the  spaces  under  the  19  central  arches 
between  the  piers  carrying  the  roadway 
over  the  dam  have  been  adapted,  form- 
ing a  weir  456  ft.  in  length.  The  surplus 
water  thus  falls  down  the  outer  face  of 
the  dam,  which  has  been  given  a  curved 
section  to  receive  the  shock  of  the  falling 
water. 

A  BYE-CHANNEL  formed  in  cutting  around 
the  side  of  a  reservoir,  as  illustrated  in 
Fig.  4,  is  a  necessary  accessory 
work  for  the  purpose  of  carrying 
awray  the  flood  discharge  of  the 
stream  feeding  the  reservoir  and 
for  diverting  the  turbid  and  dis- 
coloured waters  into  the  stream 
below  the  dam.  It  is  also  a  great 
convenience  as  a  by-pass  during 
the  construction  of  an  earthen 
embankment. 

These  bye-channels  are  controlled 
by  gates  or  sluices,  and  are  lined 
along  their  sides  and  bed  with 
puddle,  concrete,  or  masonry,  as 
circumstances  may  require,  in  order 
to  prevent  the  erosion  of  the  stratum 
through  which  they  may  be  formed. 

At  the  bead  of  these  bye-channels 
are  formed  small  settling  reservoirs 
termed  "residuum  lodges"  or  ponds 
(see  Fig.  4)  in  which  the  sediment  brought 
down    by    the   flood    waters    is    caught    and 
deposited  before  the  water  passes  on  to   the 
bye-channel  or  to  the  storage  reservoir.  These 
are  provided  with  sluices  or  pipes  for  empty- 
ing   them,    and   with   movable    shutters    for 
diverting    the    water    either    into    the    bye- 
channel  or  reservoir,  as  desired. 

OUTLETS  FROM  RESERVOIRS  :  VALVE  TOWERS. 
— Suitable  means  must  be  provided  for  draw- 
ing off  the  water  stored  in  a  reservoir  for 
purposes  of  supply,  and  also  for  compensation, 
and  as  a  considerable  head  of  water  has 
usually  to  be  dealt  with  the  treatment  of  the 
"outlet"  requires  to- be  carefully  considered 


in  order  to  avoid  leakage  of  the  water  under 
pressure  and  consequent  damage  to  the 
embankment  or  other  permanent  works. 

Outlet  culverts  at  one  time  were  commonly 
laid  through  the  base  of  the  dam,  at  its  lowest 
part,  and  thus  afforded  a  convenient  means  of 
draining  off  the  water  coming  down  during 
the  construction  of  the  dam.  Outlets  so 
placed  are,  however,  liable  to  be  damaged  by 
the  unequal  settlement  of  the  embankment, 
especially  at  the  point  of  passing  through  the 
puddle  wall,  and  leakage  of  water  under  pres- 
sure is  almost  certain  to  result,  leading  to 


Pool 


PLAN 


SECTION 

FIGS.  5  and  6. — Waste  Water  Course,  with  Pools. 

subsidence  and  ultimately  to  the  destruction 
of  the  dam.  The  prospect  of  failure  is  even 
greater  when  the  valves  controlling  the  dis- 
charge are  placed  at  the  outer  end  of  the  out- 
let, or  in  the  centre  of  the  embankment  pre- 
venting access  to  the  culvert  for  repairs.  The 
outlet,  whether  consisting  of  a  culvert  or 
pipe,  should  be  controlled  throughout  its 
length  by  a  valve  tower  placed  at  its  inner 
end  within  the  reservoir. 

The  safest  though  most  costly  plan,  where 
a  reservoir  is  formed  of  an  earthen  embank- 
ment, is  to  carry  the  culvert  through  a  tunnel 
round  the  end  of  the  embankment,  or  through 
the  side  of  the  valley  into  another  watershed 


535 


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ENCYCLOPEDIA   OF 


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if  the  conditions  are  favourable,  and  to  control 
the  discharge  by  a  valve  tower  within  the 
reservoir,  having  inlets  at  different  levels  so 
that  the  water  may  be  drawn  off  at  various 
depths  as  desired.  In  the  Villar  masonry 
dam  on  the  Lozoya  for  the  supply  of  Madrid, 
and  in  the  New  Croton  dam  (New  York),  the 
outlets  are  carried  through  the  dams  at  a  low 
level  with  the  valve  chambers  formed  in  the 
dam.  A  better  plan,  however,  is  to  carry  the 
culvert  in  a  tunnel  at  one  side  of  the  valley 
beyond  the  dam,  as  done  in  the  case  of  the 
Vyrnwy  reservoir,  where  the  flow  is  controlled 
and  strained  through  copper  wire  gauze  in  a 
masonry  tower  built  in  the  reservoir.  The 
compensation  water  here  is  discharged  by 
means  of  a  culvert  carried  through  the  dam 
direct  into  the  river  below. 

The  proper  arrangement  of  the  outlet  is  a 
very  important  part  of  the  design  of  a  dam, 
and  serious  failures  have  resulted  from 
unequal  settlement  near  the  culvert  and 
infiltration  of  pressure  water  into  the  bank. 
The  bursting  of  the  Dale  Dike  embankment, 
near  Sheffield,  in  1864,  on  the  occasion  of  the 
first  filling  of  the  reservoir  was  attributed  to 
the  unequal  settlement  and  cracking  of  the 
puddle  wall  over  the  trench  excavated  in  the 
rock  in  which  the  outlet  pipes  had  been  laid. 
Other  causes  contributing  to  this  failure  were 
the  defective  material  used  for  the  bank  and 
the  rough  way  in  which  it  was  raised,  also 
the  rapid  filling  of  the  reservoir.  The  em- 
bankment was  95  ft.  high  and  the  reservoir 
had  a  capacity  of  114  million  cubic  feet. 

Another  instance  of  failure  was  the  embank- 
ment across  the  Lynde  Brook,  Worcester, 
Mass.,  which  burst  in  1876  and  released  a 
reservoir  of  110  million  cubic  feet  capacity, 
owing  to  the  gradual  percolation  of  the  water 
under  pressure  along  the  line  of  outlet  pipes. 

VALVE  TOWER. — The  outlet  culvert  from  a 
reservoir  is  usually  connected  at  its  inner  or 
upstream  end  with  a  "  valve  tower  "  which 
contains  the  supply  and  scour  pipes,  straining 
screens,  and  valves  for  working  the  outlet  works 
of  the  reservoir.  The  tower  is  also  provided 
with  a  vertical  cast-iron  pipe  (an  extension  of 


the  outlet  pipe  through  the  culvert)  into  which 
branches,  controlled  by  valves  worked  from 
the  valve  chamber  just  above  top  water  level, 
are  connected  in  a  manner  enabling  the  water 
to  be  drawn  off  at  different  levels  as  may  be 
required.  The  tower  is  usually  circular  in 
plan  and  is  built  of  masonry,  brickwork,  con- 
crete, or  cast  iron. 

SIPHON  OUTLETS. — Where  a  reservoir  doc 
not  exceed  about  25  ft.  in  depth,  the  wat( 


Av -outlet,  provision, 
'  for  charging  etc. 

outlet' 
•Vali 


^Puddle.  ujaZl 

FIG.  7. — Siphon  Outlet  from  Reservoir. 

may  be  drawn  off  by  a  siphon  pipe  placed  a£ 
shown  in  Fig.  7 ;  that  is,  carried  up  the 
inner  slopes  of  the  dam,  over  the  top,  and 
down  the  outer  slope  to  a  lower  level  than  the 
bottom  of  the  reservoir.  There  must,  of  course, 
be  sufficient  difference  of  head  between  the 
two  legs  of  the  siphon  to  overcome  friction  and 
to  give  the  required  discharge.  Water  may 
be  drawn  off  at  any  level  by  means  of  valves 
suitably  placed  on  the  inner  slope  as  illus- 
strated.  To  start  the  siphon  the  valves  at 
both  ends  are  closed  and  the  pipe  filled  with 
water  from  the  top  of  the  embankment  where 
a  charging  valve  and  air-vessel  are  placed. 
The  discharge  will  be  started  by  closing  the 
valve  at  the  top  of  the  siphon  and  opening  the 
others,  but  the  summit  must  be  kept  free  of  air 
which  will  accumulate  there  and  throttle  the 
flow  unless  means  are  provided  for  its  removal. 
The  siphon  may  also  be  started  by  exhausting 
the  air  from  the  summit  valve  by  means  of  an 
air-pump. 

Siphon  outlets  have  the  advantage  of  not 
interfering  with  the  embankment  below  high 
water  mark,  but  they  usually  require  a  good 
deal  of  attention  and  are  not  generally 
satisfactory. 

CREEPING  FLANGE  OR  PUDDLE  COLLAR. — The 
outlet  culvert  from  a  reservoir  is  stopped  at 
some  point  in  its  length  by  a  plug  of  concrete 


536 


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MUNICIPAL   AND    SANITARY   ENGINEERING. 


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or  brickwork,  through  which  the  outlet  pipe 
passes.  The  main  passing  through  this  plug 
should  have  cast  upon  it,  or  bolted  around  it, 
a  deep  projecting  flange  known  as  a  "  puddle 
plate  "  or  creeping  flange  (Fig.  8)  to  prevent 
the  leakage  of  water  along  the  pipe. 

LEAPING  OK  SEPARATING  WEIRS  are  employed 
for  the  purpose  of  automatically  rejecting 
flood  waters  from  a  collecting  conduit.  (See 
article  "LEAPING  WEIR.") 

AQUEDUCTS. — In  a  gravitation  scheme  the 
water  is  usually  stored  in  a  lake  or  reservoir 
formed  in  a  valley  situate  in  hilly  ground  at  a 
considerable  elevation  above  sea  level,  and  aliso 
usually  at  a  distance  of  many  miles  from  the 
town  to  be  supplied.  The  supply  has,  there- 
fore, to  be  conveyed  by  means  of  an  "  aque- 
duct"  to  the  service  reservoirs  in  the  imme- 
diate vicinity  of  the  town,  whence  the  water 
again  flows  by  gravitation  into  the  distributing 
mains,  and  is  delivered  at  a  pressure  (depend- 
ing on  the  relative  heights  of  the  service 
reservoir  and  of  the  area  of  distribution) 
sufficient  to  reach  the  uppermost  storeys  of 
the  highest  houses. 

As  formerly  applied,  the  term  "  aqueduct" 
related  more  particularly  to  structures  like  the 
bold  masonry  bridges  erected  by  the  Romans 
for  the  conveyance  of  water  across  deep 
valleys,  and  to  similar  channels  for  purposes 
of  irrigation  and  navigation.  In  its  present 


FIG.  8. — Creeping  Flauge,  or  Puddle  Collar. 

and  more  extended  sense  an  aqueduct  com- 
prises, in  addition  to  bridges,  open  or  covered 
channels  or  conduits,  tunnels,  and  metal  pipe 
lines,  now  largely  employed  upon  gravitation 
schemes  of  water  supply. 

The  internal  sectional  dimensions  of  an 
aqueduct  for  tbe  conveyance  of  a  given  volume 
of  water  will  depend  principally  upon  the 
"  hydraulic  gradient  "  which  can  be  given  to 


the  conduit.  The  hydraulic  gradient  is 
expressed  in  feet  or  inches  of  fall  per  mile  of 
length,  and  is  the  vertical  fall  between  any 
two  points  on  the  line  of  aqueduct  divided  by 
the  length.  The  hydraulic  gradient  may  be 
maintained  throughout  if  the  aqueduct  is  con- 
structed of  the  same  cross  section  along  its 
whole  length,  but  it  is  frequently  desirable  to 
vary  the  gradient  at  different  parts,  on  grounds 
of  economy  in  construction,  in  order  that  the 
level  of  the  work  may  be  more  nearly  adjusted 
to  the  configuration  of  the  ground  or  that  the 
section  of  the  tunnel,  conduit,  or  pipes  may 
be  reduced  in  places. 

An  outline  section  of  a  modern  aqueduct  as 
constructed  for  a  gravitation  water  supply 
scheme  is  given  in  Fig.  9,  which  represents 
the  profile  of  the  ground  surface  along  the 
line  of  the  aqueduct  from  Lake  Yyrnwy  to 
Liverpool. 

Such  aqueducts  consist  of  a  channel  con- 
structed to  the  inclination  of  the  hydraulic 
gradient,  and  carried  through  hills  or  rising 
ground  in  tunnel  ;  contouring  hillside  slopes 
or  passing  through  fairly  level  ground  in  open 
cutting  or  cut-and-cover  work ;  or,  where  the 
ground  suddenly  dips  below  the  hydraulic 
gradient  as  shown  at  many  places  in  the  figure, 
the  form  of  the  aqueduct  changes  to  a  series  of 
iron  pipes  laid  side  by  side  and  following  the 
contour  of  the  ground  surface  with  no  greater 
depth  of  cover  than  is  needed  for  protection 
against  damage,  instead  of  bridging  the  valley 
by  means  of  a  huge  arched  bridge  following  the 
hydraulic  gradient  as  in  the  early  Roman  works. 
The  pipe  lines  are  of  cast  iron  or  riveted 
wrought  steel  tubes  and  form  large  inverted 
siphons,  often  many  miles  in  length,  through 
which  the  water  flows  under  a  pressure 
depending  upon  the  depth  at  which  they  are 
laid  below  the  hydraulic  grade  line. 

The  form  of  aqueduct  at  various  points 
along  the  line  will  depend  upon  the  con- 
figuration of  the  ground.  Where  this  is 
fairly  uniform,  the  hydraulic  gradient  will 
be  followed  by  contouring  the  slopes  in  a 
more  or  less  circuitous  route,  and  the  high 
ridges  will  be  pierced  by  tunnelling,  pipes 


537 


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ENCYCLOPAEDIA   OF 


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being  resorted  to  only  when  a   deep  valley  straight  course,  except  at  the  points  where  the 

has  to  be  crossed.  level  rises  above  the  hydraulic  gradient  (above 

In  the  case  of  the  above  aqueduct  it  will  be  which  the  aqueduct  must  not  rise),  and  here 

seen    that    the    land    mostly  lies   below  the  tunnelling  is  resorted  to  and  the  invert  of  the 


Z7  Z8  Z9  30  31  3Z  i3 


J.      T>  ?    7 


HORIZONTAL     SCALE 


66  67 


VERTICAL     SCALE 
""?",  ,  i  ,*%*!       1 9 "f0 


FIG.  9. — Vyrnwy  Aqueduct.     Longitudinal  Section. 

hydraulic  grade  line  shortly  after  leaving  aqueduct  coincides  with  the  hydraulic  gradient, 
the  lake  except  at  a  point  just  before  reaching  The  hydraulic  gradient  is  also  reached  (see 
Oswestry.  In  such  a  case  the  aqueduct  con-  Fig.  9)  at  several  points  on  the  pipe  line 
sists  mostly  of  pipes  following  the  irregular!-  where  "  balancing  reservoirs  "  are  introduced 
ties  of  the  ground  and  following  a  fairly  for  the  purpose  of  reducing  the  pressure  of 

538 


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MUNICIPAL   AND   SANITARY  ENGINEERING. 


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the  water  on  the  lowest  part  of  the  pipes  by 
thus  breaking  up  the  fall  of  the  aqueduct  into 
independent  sections. 

The  plan  of  following  the  hydraulic  gradient 
usually  involves  a  large  amount  of  cutting  for 
the  conduit,  and  it  frequently  becomes  neces- 
sary to  follow  a  more  circuitous  route  by 
contouring  the  hill  slopes  to  avoid  sudden 
changes  of  level  in  the  ground,  but  balancing 
reservoirs  are  not  required  upon  this  method 
of  constructing  an  aqueduct.  Where  a  pipe 
line  is  adopted,  a  straighter  and  shorter  course 
is  obtainable  and  the  available  gradient  is 
consequently  greater.  There  is,  however,  a 
greater  loss  of  head  owing  to  the  frictional 
resistance  in  the  pipes,  and  a  greater  water 
section  is  therefore  required  for  the  same 
amount  of  discharge.  In  a  pipe  line,  also, 
the  pressure  at  the  lowest  point 
may  become  unduly  great  if  not 
relieved  by  balancing  reservoirs  at 
suitable  intervals. 

Some    of    the    most    important 
aqueducts  in  this  country  for  water 
supply  purposes  are  the  two  from 
Loch  Katrine  to  Glasgow  (24  miles), 
from  Thirlmere  to  Manchester  (96 
miles),     from      Nidd      Valley      to 
Bradford  (32    miles),  from   Lake  Vyrnwy  to 
Liverpool  (68J   miles),   from   Elan  Valley  to 
Birmingham   (74   miles),  and  from  Derwent 
Valley  to  Leicester  (about  72  miles). 

The  Thirlmere  aqueduct  contains  about 
14*2  miles  of  tunnels,  36'75  miles  of  covered 
conduit,  and  about  45  miles  of  48  in.,  40  in., 
and  36  in.  cast-iron  pipes,  laid  as  inverted 
siphons  through  the  valleys.  The  siphon 
across  the  valley  of  the  Ribble  is  9J  miles 
long,  and  that  across  the  valley  of  the  river 
Lune  has  a  dip  giving  a  maximum  head  of 
water  of  427  ft.,  equal  to  a  pressure  of  about 
186  Ibs.  to  the  square  inch.  The  pipes  are 
mostly  carried  over  the  rivers  at  the  bottom  of 
the  valleys  on  bridges,  so  that  they  are  readily 
accessible  for  inspection  and  repairs.  For 
about  83  miles  from  Thirlmere  a  hydraulic 
gradient  of  20  in.  per  mile  is  maintained,  but 
in  the  remaining  13f  miles  there  is  an  avail- 


able fall  of  about  32  in.  per  mile,  and  the 
diameter  of  this  line  of  piping  is  consequently 
reduced  to  36  in. 

The  siphons  connect  with  the  conduits 
through  rectangular  chambers  formed  at  each 
end,  and  an  automatic  valve  shuts  off  the 
supply  in  the  event  of  the  bursting  of  a  pipe 
in  the  line  of  siphon. 

The  conduits  are  about  7  ft.  by  7  ft.  internal 
dimensions,  and  are  formed  of  concrete  on  the 
cut-and-cover  system  with  the  portions  in 
tunnel  lined  with  concrete.  The  aqueduct  is 
carried  across  small  streams  on  masonry 
bridges,  and  a  uniform  gradient  of  20  in.  per 
mile  is  maintained. 

The  Vyrnwy  aqueduct  is  divided  into  six 
sections  by  "  balancing  reservoirs "  con- 
structed on  sites  where  the  land  attains  the 


FIG.  10. — Hydraulic  Gradient  of  Pipe  Line. 

level  of  the  hydraulic  gradient.  It  happened, 
however,  that  there  was  no  land  along  the  last 
20^  miles  of  the  aqueduct  of  a  sufficient  height 
to  reach  the  hydraulic  gradient,  and  it  thus 
became  necessary,  in  order  to  make  a  break  in 
the  long  line  of  pipes  under  pressure  between 
the  Cotebrook  Balancing  Reservoir  and  the 
Prescot  Service  Reservoirs,  to  form  a  "  balanc- 
ing reservoir  "  on  the  top  of  a  high  towrer, 
shown  in  the  section  (Fig.  9),  on  the  summit 
of  Norton  Hill,  situate  about  3  miles  to  the  east 
of  Runcorn  between  the  valleys  of  the  rivers 
Weaver  and  Mersey.  By  this  means  the 
reservoir  is  raised  to  the  hydraulic  gradient, 
which  at  that  point  is  110  ft.  above  the  sur- 
face of  the  ground.  The  reservoir  consists  of 
a  circular  basin  80  ft.  in  diameter,  formed  of 
steel  plates,  and  having  a  central  depth  of 
31  ft.  The  hydraulic  gradient  on  this  aque- 
duct varies  from  2  ft.  per  mile  in  the  tunnels 


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ENCYCLOPAEDIA   OF 


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to  6'87  ft.  per  mile  in  the  long  siphon  between 
the  Oswestry  reservoir  and  the  Malpas  tank. 
The  pipe  line  will  ultimately  consist  of  three 
lines  of  pipes,  and  their  diameters  range  from 
32  in.  to  42  in.,  according  to  the  amount  of 
fall  available  in  the  different  sections.  In  the 
case  of  a  burst  pipe,  automatic  valves  worked 
by  the  fall  of  a  float  gradually  shut  off  the 
supply,  and  air  valves  fixed  at  all  the  summits 
of  the  siphons  are  provided  for  the  escape  of 
the  air  which  otherwise  accumulates  in  the 
mains  at  the  high  points  and  throttles  the 
flow  of  the  water. 

The  aqueduct  from  Elan  Valley  to  Birming- 
ham has  a  hydraulic  gradient  of  only  15'84in. 
per  mile  in  the  tunnels  and  conduits,  but  in 
the  siphons  the  gradient  is  increased  to  36  in. 
per  mile,  and  will  consist  of  six  lines  of  42  in. 
metal  pipes.  The  total  ultimate  supply 
through  this  aqueduct  is  to  be  75,000,000 
gallons  per  day ;  that  through  the  Vyrnwy 
aqueduct  is  40,000,000  per  day,  and  50,000,000 
from  Thirlmere  to  Manchester.  On  the  Elan 
aqueduct  the  longest  siphon  is  17  miles  in 
length,  and  the  greatest  dip  of  the  pipe  line  is 
550  ft.  below  the  hydraulic  gradient,  where  the 
Severn  is  crossed  by  a  bridge  near  Bewdley. 

SERVICE  EESERVOIRS. — As  mentioned  already, 
the  service  reservoir  is  usually  situate  in  the 
immediate  vicinity  of  the  town  supplied,  and 
is  constructed  upon  the  best  available  site  of 
such  an  elevation  as  will  be  capable  of  deliver- 
ing a  supply  of  water  by  gravitation  to  the 
highest  houses  within  the  water  area.  Where  a 
town  consists  of  widely  varying  levels  it  is  well 
to  divide  the  water  area  into  various  high, 
middle,  and  low-level  districts,  or  "  zones  "  of 
supply,  and  to  provide  a  separate  reservoir  for 
each  if  the  conditions  render  such  a  system 
economical.  By  this  means  the  cost  of  pump- 
ing to  unnecessary  heights  will  be  avoided,  as 
also  the  excessive  pressures  otherwise  obtained 
in  the  lower  parts  of  the  town,  which  often 
cause  much  waste  of  water  through  weak  or 
defective  fittings. 

The  main  objects  of  a  service  reservoir  are, 
(a)  to  maintain  a  small  storage  of  water  near 
the  town  to  provide  against  irregularities  of 


consumption  and  to  form  a  reserve  to  be 
drawn  upon  in  cases  of  sudden  demand,  as  the 
outbreak  of  fire,  or  to  meet  an  emergency, 
such  as  the  bursting  of  a  rising  main,  the 
failure  of  an  aqueduct,  or  of  the  pumping 
machinery  delivering  to  the  reservoir ;  (b)  to 
give  a  fairly  constant  head  on  the  suppl} 
mains,  thus  equalising  the  pressure  thereii 
which  cannot  be  secured  by  pumping  directb 
into  the  mains  ;  (c)  to  enable  the  pumping 
machinery  to  work  at  a  fairly  uniform  anc 
economical  rate,  and  to  avoid  night  pumping 

The  rate  of  consumption  of  water  varie 
according  to  the  requirements  of  the  to\ 
supplied  and  the  extent  to  which  trade  anc 
municipal  supplies  are  connected  to  the 
system,  but  the  demand  is  usually  largest 
during  the  morning  hours,  commencing  to 
increase  at  about  6  A.M.,  and  reaching  a 
maximum  somewhere  near  10  A.M.  There 
will  be  various  fluctuations  during  the  re- 
mainder of  the  day,  and  the  minimum  supply 
will  pass  out  during  the  night  or  early  morn- 
ing from  1  A.M  to  4  A.M.  By  making  a  careful 
comparison  of  the  quantity  given  out  during 
these  4  hours  a  good  idea  of  the  percentage 
and  variations  in  the  daily  waste  may  be 
obtained.  On  the  average  it  is  found  that 
rather  more  than  twice  as  much  water  is 
consumed  between  the  hours  of  6  A.M.  and 
6  P.M.  as  between  6  P.M.  and  6  A.M. 

A  service  reservoir  should  hold  from  1  to  3 
days'  ordinary  supply,  or  more  if  for  any 
local  circumstance  the  conveyance  of  water 
to  the  reservoir  is  liable  to  interruption.  The 
reservoir  is  usually  formed  by  excavating 
and  building  about  half  its  depth  below  the 
ground  surface  and  embanking  the  upper  half 
above  the  ground  line  with  the  excavated 
material.  The  walls  are  built  of  concrete  or 
brickwork,  sometimes  backed  with  clay  puddle, 
and  rendered  internally  with  cement  or  bitu- 
minous sheeting.  Seeing  that  the  situation 
of  service  reservoirs  is  close  to  inhabited  areas, 
they  should  nearly  always  be  covered  to 
prevent  pollution  of  the  water  by  dust,  soot,  or 
other  objectionable  matter,  and  the  water  is 
thus  kept  at  a  more  uniform  temperature, 


540 


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MUNICIPAL   AND   SANITAEY  ENGINEERING. 


WAT 


cooler  in  summer,  and  less  liable  to  frost  in 
winter.  The  depth  of  the  water  therein  should 
be  not  less  than  from  12  ft.  to  15  ft.,  sufficient 
to  impede  the  growth  of  animal  and  vegetable 
life. 

There  are  many  ways  of  covering  reservoirs, 
amongst  which  may  be  mentioned  a  wood  roof, 
with  slates,  concrete  arches  and  piers,  concrete 
arches  or  slabs  carried  by  girders  and  joists, 
girders  and  jack  arches,  corrugated  iron  on 
light  iron  trusses,  and  expanded  metal  and 
concrete  carried  by  girders  and  iron  columns. 

The  various  accessory  details  connected 
with  a  service  reservoir  include  an  inlet,  out- 
let, overflow,  scour  or  wash-out  pipe,  access 
ladder,  manholes  and  ventilators,  and  water- 
level  indicator.  A  good  plan  is  to  surround 
the  inlet  by  a  dwarf  wall  to  retain  a  small 
quantity  of  water  which  will  act  as  a  cushion 
for  the  incoming  water  to  fall  upon.  The 
outlet  should  be  a  few  inches  above  the  level 
of  the  floor  and  guarded  by  a  close  wire 
screen.  Manholes  for  access  and  light  during 
cleaning  and  repairs  should  be  provided,  and 
the  reservoir  should  be  well  ventilated.  The 
water  level  in  the  reservoir  is  now  very 
generally  recorded  by  means  of  an  electric 
water-level  indicator  connected  direct  with  the 
pumping  station  or  the  water  engineer's  office. 
It  is  a  good  plan  to  have  a  large  reservoir 
divided  by  means  of  a  dwarf  wall  so  that  one- 
half  may  be  used  for  maintaining  a  constant 
head  on  the  supply  mains  whilst  the  other 
half  is  under  repair  or  being  cleaned. 

Circular  reservoirs  are  more  economical  to 
construct  than  rectangular  ones,  as  the  thick- 
ness of  the  walls  may  be  much  reduced.  Taking 
the  thickness  of  straight  Avails  in  rectangular 
service  reservoirs  as  varying  between  one- 
fourth  and  two-fifths  of  the  depth,  those  of 
circular  reservoirs  have  been  found  strong 
enough  with  a  thickness  of  from  one-sixth  to 
one-tenth  of  the  depth.  In  construction, 
circular  reservoirs  will  be  found  to  be  from 
20  to  40  %  cheaper  than  those  of  a  rectangular 
design,  but  are  not,  of  course,  so  economical 
in  ground  space. 

The    cost    of   a   covered    service   reservoir 


541 


varies  from  about  £2  up  to  as  much  as  £10 
per  1,000  gallons  capacity,  depending  very 
largely  upon  local  circumstances  and  the  size 
of  the  reservoir.  About  £5  per  1 ,000  gallons 
may  be  taken  as  a  fair  average  price  under 
ordinary  conditions. 

Concrete,  when  made  of  good  clean 
materials,  is  a  very  useful  material  for  the 
construction  of  a  service  reservoir.  A  circular 
reservoir  of  550,000  gallons  available  capacity 
formed  of  this  material  at  Upwey  for  the 
Portland  Urban  District  Council  was  built 
entirely  of  concrete  composed  of  6  parts 
Moreton  gravel  to  1  part  of  Portland  cement. 
The  reservoir  is  90ft.  internal  diameter  with 
a  depth  of  water  of  16  ft.  The  external  wall 
is  3  ft.  thick,  and  the  floor,  which  slopes 
towards  a  wash-out  pipe,  is  1  ft.  in  thickness. 
The  roof  is  of  concrete  arches  of  8  ft.  clear 
span  and  1  ft.  thick,  and  is  carried  by  eight 
cross  walls  1  ft.  6  in.  thick  pierced  with 
openings  10  ft.  by  8  ft.  The  internal  surfaces 
are  rendered  with  two  coats  of  Portland  cement 
mortar,  the  first  coat,  f  in.  thick,  being  com- 
posed of  1  part  cement  to  2  parts  sand  ;  and 
the  second  coat  J  in.  thick,  of  1  part  cement  to  1 
part  sand,  and  trowelled  to  a  hard  smooth 
surface.  The  reservoir  is  well  ventilated, 
and  lighted  from  the  crown  of  the  arches,  and  a 
valve  chamber  is  formed  outside  the  reservoir 
through  which  passes  the  rising  and  delivery 
mains.  Water  is  admitted  to  and  flows  from  the 
reservoir  by  a  floating  arm,  and  is  thus 
always  drawn  from  about  9  in.  below  the 
surface  so  that  no  sediment  or  floating  matter 
can  enter  the  supply  mains.  A  Jennings'  patent 
electrical  mechanical  indicator  and  recorder  is 
fixed  at  the  pumping  station,  and  is  elec- 
trically connected  with  the  reservoir,  so  that 
the  quantity  of  water  in  the  reservoir  is  always 
known  to  the  man  in  charge  at  the  pumping 
station.  This  reservoir  cost  £2,270,  or 
£4  2s.  6d.  per  1,000  gallons. 

DISTRIBUTION  OF  WATEK. — A  water  supply, 
having  been  delivered  to  a  service  reservoir 
of  sufficient  elevation  to  command  the  area  of 
supply,  is  distributed  by  means  of  cast-iron 
lead -jointed  mains  throughout  the  water  area. 


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ENCYCLOPEDIA   OF 


WAT 


The  first  consideration  is  to  decide  upon  the 
best  routes  and  determine  the  requisite  sizes 
of  the  leading  trunk  mains,  having  due  regard 
to  the  elevation  of  the  various  streets  to  be 
supplied,  and  the  present  and  future  popula- 
tion to  be  connected  thereto.  For  branch 
mains  supplying  a  single  street,  3  in.,  4  in., 
or  5  in.  diameter  pipes  will  usually  be 
sufficient,  but  the  sizes  of  leading  mains  will 
vary  considerably  according  to  the  districts 
fed  by  them,  and  each  case  will  involve  special 
investigation. 

Where  there  is  no  special  provision  in  the 
way  of  a  subway  under  a  street,  a  good 
position  for  the  water  main  is  in  the  roadway 
at  a  distance  of  about  3  ft.  from  the  curbing. 
The  mains  should  be  laid  with  a  minimum  of 
2  ft.  6  in.  or  3  ft.  of  cover  as  a  protection 
against  frost  and  damage  from  heavy  traffic, 
and  the  pipes  should  be  thoroughly  well 
coated  with  Dr.  Angus  Smith's  solution  or 
other  like  preservative  and  have  a  thickness 
of  metal  adequate  for  the  water  pressure  to 
which  the  pipes  will  be  subjected. 

Whilst  some  distinction  might  be  made  in 
the  thicknesses  of  metal  between  two  entirely 
separate  zones  of  supply  having  widely 
varying  pressures,  it  will  be  unwise  to  attempt 
to  differentiate  between  the  pressures  of  the 
same  area,  otherwise  great  confusion  may 
easily  arise  for  the  want  of  standard  sizes  in 
the  spigots  and  sockets  of  pipes,  and  thus  lead 
to  much  inconvenience  and  delay  in  the 
execution  of  repairs.  Another  objection  to 
reducing  the  standard  thicknesses  is  that 
water  at  a  higher  pressure  may  upon  an 
emergency,  such  as  a  fire,  require  to  be  turned 
into  the  low  pressure  district.  In  very  wide 
streets  with  much  traffic  it  is  not  unusual  to 
have  a  large  leading  main  near  the  centre  of 
the  roadway  with  smaller  tapping  mains  on 
each  side  in  or  near  the  footpath,  to  which 
are  connected  the  house  supplies,  thus 
leaving  the  trunk  main  exclusively  for  the 
supply  to  districts  beyond.  The  pressure  in 
the  leading  main  is  thus  maintained  and  the 
inconvenience  and  cost  of  crossing  the  street 
to  make  house  connections  is  avoided. 


In  laying  out  a  distribution  system  it  is 
important  to  provide  adequate  main  capacity, 
bearing  in  mind  that  it  is  the  maximum 
summer  supply  during  any  hour  of  the  day 
which  must  be  provided  for  and  not  the 
average  of  the  year,  month,  or  week.  The 
maximum  rate  of  draught  may  be  taken 
approximately  at  double  the  average  consump- 
tion of  24  hours,  and  mains  must  be  of  sufficient 
capacity  to  deliver  the  requisite  quantity  at  the 
required  pressure  during  all  periods  of  the  day. 
In  long  lengths  of  small-sized  mains  the 
frictional  losses  at  the  time  of  heaviest  draught 
will  be  considerable,  and  the  size  of  the  mains 
should  be  such  that  not  more  than  about  one- 
fourth  of  the  available  statical  head  should  be 
consumed  in  overcoming  friction. 

In  addition  to  the  ordinary  supply  it  must 
be  remembered  that  a  heavy  draught  will  also 
be  made  at  times  for  street  watering  purposes 
and  that  this  usually  occurs  at  the  time  when 
domestic  supplies  are  at  a  maximum.  It  is 
necessary,  therefore,  that  the  pressure  should 
at  all  times  be  sufficient  to  reach  the  highest 
storeys  of  premises  within  the  distribution  area. 

In  districts  where  there  is  great  variation 
of  levels  it  usually  becomes  necessary  to  divide 
the  area  into  separate  districts  or  "  zones  of 
supply"  so  as  to  maintain  pressures  in  the 
mains  suited  to  these  different  areas,  otherwise 
an  excessive  pressure  will  obtain  in  the  lower 
areas.  As  a  maximum  pressure  a  head  of 
about  200  ft.,  equivalent  to  86  Ibs.  to  the 
square  inch,  may  be  adopted.  Water  fittings 
in  general  use  will  not  satisfactorily  withstand 
a  head  much  beyond  this  figure  under  ordinary 
working  conditions  without  great  waste  of 
water.  The  different  zones  of  a  district, 
usually  designated  "high-level,"  "middle," 
and  "  low-level "  according  to  circumstances, 
are  supplied  by  means  of  service  reservoirs, 
water-towers,  and  stand-pipes  suitably  placed 
to  command  the  various  levels. 

A  "  stand-pipe  "  supply  is  given  by  placing 
a  vertical  pipe  (in  the  form  of  an  inverted  I  ) 
in  the  line  of  rising  main,  and  the  water 
pumped  against  the  additional  head  due  to  tin 
height  of  the  stand-pipe,  and  a  corresponding 


542 


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MUNICIPAL   AND   SANITARY   ENGINEERING. 


WAT 


increase  of  pressure  is  thus  afforded  for  houses 
lying  at  a  greater  elevation  than  the  service 
reservoir.  The  surplus  water  passing  over 
the  top  of  the  stand-pipe  falls  through  the 
down  leg  and  enters  the  service  reservoir. 
Where  a  considerable  area  at  the  higher  level 
has  to  be  supplied  it  is  preferable  to  have 
more  high-level  storage  than  is  afforded  by 
a  stand-pipe,  and  for  this  purpose  a  "water- 
rower"  is  substituted  (see  "STAND-PIPE  AND 

AIR-VESSEL"). 

By  zoning  a  district  in  this  way  the  cost  of 
raising  the  whole  supply  to  one  high-level 
reservoir  is  avoided,  and  the  pressures  are 
maintained  more  uniformly  throughout,  but 
some  additional  complication  and  expense  may 
be  involved  in  the  daily  working  of  the 
different  levels,  so  that  it  becomes  desirable  to 
confine  the  number  of  zones  within  the  limits 
of  absolute  necessity. 

In  laying  out  a  pipeline,  care  should  be  taken 
that  no  part  of  the  line  rises  above  the  mean 
hydraulic  gradient  or  the  discharge  will  be 
impaired  or  perhaps  be  nil.  The  hydraulic 
gradient  is  represented  by  a  straight  line 
drawn  from  the  point  where  the  water  enters 
the  pipe  line  (as  B.,  Fig.  10)  to  the  termination 
of  the  line  at  its  point  of  discharge,  C.  When 
the  pipe  line  is  below  the  hydraulic  gradient 
the  discharge  at  C  will  be  that  due  .to  the 
hydraulic  gradient  B  C.  If,  however,  the 
ground  rises  to  a  point  such  as  at  A,  the 
hydraulic  gradient  B  C  will  no  longer  govern 
the  discharge,  which  will  be  limited  to  that 
due  to  the  natter  gradient  B  A.  The 
remaining  and  steeper  portion  A  C  of  the  pipe 
line  BAG  may  therefore  be  of  a  less  diameter 
than  that  from  B  to  A  to  give  an  equal  dis- 
charge. It  is  therefore  readily  seen  that  the 
section  of  a  line  of  main  should  be  plotted 
and  the  hydraulic  gradients  obtainable  well 
considered  before  the  sizes  of  the  different 
sections  of  a  pipe  line  are  finally  decided  upon, 
otherwise  an  insufficient  discharge  may  result 
or  an  unnecessary  expense  may  be  incurred  by 
continuing  a  main  of  large  diameter  when  one 
of  a  smaller  section  would  have  proved 
adequate. 


The  delivery  of  water  mains  of  various 
sizes  and  hydraulic  gradients  is  obtained  in 
practice  from  hydraulic  tables  based  on  the 
results  calculated  from  empirical  formula 
arrived  at  by  various  experimenters  in 
hydraulic  science.  Space  will  not  permit  of 
more  than  a  mere  mention  of  the  subject  here, 
but  reference  should  be  made  to  works  specially 
devoted  thereto.1  The  formula  now  commonly 
used  is  Herr  Kutter's,  which  gives  more 
correct  results  than  the  older  formula?  and 
takes  into  account  the  degree  of  roughness  of 
the  internal  walls  of  the  pipes.  Speaking 
generally,  the  difference  between  Kutter's  and 
the  older  formulae  is  that  it  gives  smaller 
discharges  for  small  diameters,  and  larger 
discharges  for  large  diameters. 

INTERMITTENT  SUPPLY. — Water  supplies  were 
formerly  delivered  to  consumers  at  short 
intermittent  periods  of  the  day,  during  which 
the  storage  cisterns  of  dwelling-houses  were 
filled  for  the  use  of  the  household  until  a 
further  supply  from  the  main  was  again  avail- 
able. The  object  of  the  system  was  to  prevent 
waste  and  to  economise  water,  but  there  were 
many  drawbacks  to  this  method,  particularly 
from  a  sanitary  point  of  view,  and  it  has  now 
become  almost  obsolete.  The  principal  objec- 
tions to  an  intermittent  service  are — (1)  the 
storage  of  considerable  quantities  of  drinking 
water  oftentimes  in  more  or  less  unsuitable 
and  dirty  receptacles  ;  (2)  the  risk  of  pollution 
of  the  water  owing  to  the  mains  and  service 
pipes  being  alternately  empty  and  charged, 
thus  producing  at  times  an  inward  suction  in 
the  case  of  leaky  pipes.  The  intermittent 
system  is  seldom  resorted  to  at  the  present 
day  except  under  absolute  necessity  during 
periods  of  shortage  of  water. 

CONSTANT    SUPPLY. — The   efforts    of    water 

144  Water-pipe  Discharge  Diagrams"  (Kutter's 
formula),  by  E.  B.  &  G.  M.  Taylor,  Civil  Engineers 
(published  by  B.  T.  Batsford).  4<  Hydraulic  Tables," 
by  P.  J.  Flynn,  Civil  Engineer  (E.  &  F.  N.  Spon). 
44  Practical  Hydraulics,"  by  Thomas  Box  (E.  &  F.  N. 
Spon).  'l  Tables  for  the  Solution  of  Ganguillet  and 
Kutter's  formula,"  by  Col.  E.  C.  S.  Moore,  E.E. 
(B.  T.  Batsford). 


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authorities  are  now  invariably  directed  to  the 
maintenance  of  a  "  constant  supply  "  of  water 
in  the  mains  at  a  good  pressure,  so  that  water 
may  be  drawn  by  the  consumer  direct  from 
the  main.  Occasional  temporary  interruption 
under  this  system  occurs  only  during  acci- 
dental bursting  of  a  main,  repairs,  or  altera- 
tions. To  meet  such  emergencies  it  is  advisable 
that  the  consumer  should  be  provided  with  a 
small  storage  in  well-covered  cisterns  made  of 
slate,  galvanised  iron,  or  other  suitable 
material.  Cisterns  should,  however,  be  placed 
in  a  position  readily  accessible  for  in- 
spection and  cleansing.  In  addition  to  taps 
drawing  from  storage  cisterns,  each  consumer 
should  also  be  provided  with  a  tap  for  general 
use,  taking  its  supply  direct  from  the  main. 
The  introduction  of  a  constant  water  supply 
service  at  good  pressures  has  involved  the 
necessity  for  superior  types  of  water  fittings  in 
order  to  prevent  waste  and  misuse  of  water. 
All  such  fittings  should  be  subject  to  the 
approval  of  the  water  authority,  and  be  tested 
and  stamped  before  being  passed  for  use. 

PREVENTION  OF  WASTE. — The  extent  to 
which  expense  may  be  usefully  incurred  in 
the  prevention  and  detection  of  waste  is  a 
problem  requiring  the  careful  consideration  of 
the  waterworks  engineer.  The  value  of  the 
water  thus  lost  must  be  balanced  against  the 
cost  of  the  detection  and  prevention  of  the 
waste.  Where  the  first  cost  of  the  water  is 
considerable,  or  the  quantity  limited,  the 
introduction  of  means  to  prevent  waste  will  be 
well  repaid  by  the  saving  thus  achieved,  as 
leakage  and  careless  waste,  if  unattended  to, 
are  liable  to  become  so  serious  in  the  aggregate 
as  to  materially  increase  the  annual  cost  of 
supply,  particularly  where  the  water  has  to  be 
pumped.  Moreover,  the  saving  of  waste 
enables  the  supply  to  be  extended  to  a  larger 
area,  and  tends  to  defer  the  time  when  it  will 
be  necessary  to  expend  further  capital  in 
augmenting  the  sources  of  supply.  One  of 
the  principal  means  of  detecting  and  localising 
waste  is  by  the  application  of  Deacon's  waste- 
water  meter  system,  first  introduced  at  Liver- 
pool in  1873-75.  In  this  system  the  distribu- 


tion area  is  subdivided  into  small  districts 
containing  from  2,000  to  3,000  consumers,  and 
a  waste-water  meter  fixed  in  a  by-pass  pipe  on 
the  distributing  main  supplying  this  district  at  a 
point  where  this  branch  main  leaves  the  primary 
main,  so  as  to  isolate  the  supply  to  the  sub- 
district  by  passing  it  through  the  meter.  The 
meter  contains  a  revolving  drum  upon  which 
is  automatically  recorded  the  quantity  of  water 
passing  into  the  district.  If,  during  some 
portion  of  the  night  or  during  the  small 
hours  of  the  morning,  the  consumption  so 
recorded  is  larger  than  is  reasonable  for  that 
period  of  the  24  hours,  it  may  be  safely 
inferred  that  some  unusual  draught  is  taking 
place  either  through  waste  in  the  main 
itself  or  in  household  fittings.  The  investiga- 
tion is  then  followed  up  by  an  examination 
of  the  sub-district  during  the  night,  and  each 
stop-cock  to  the  separate  premises  supplied  is 
sounded  by  using  the  valve-keys  as  stetho- 
scopes, and  any  sound  indicating  passage  of 
water  is  carefully  noted  and  traced  to  its 
origin  as  far  as  possible.  Premises  into  which 
water  is  thus  noted  to  be  passing  are  examined 
internally  on  the  following  day,  and  by  these 
means  the  location  of  waste  is  speedily  effected. 
Much  time  is  thus  saved  in  house-to-house 
inspection,  as  the  diagrams  from  many  of  the 
sub-districts  of  a  large  town  may  show  the 
conditions  to  be  normal  and  that  no  material 
waste  is  taking  place,  thereby  enabling  the 
time  of  the  inspectors  to  be  concentrated  upon 
those  areas  in  which  the  waste  is  shown  to  he 
greatest. 

FIKE. — The  demand  upon  the  water  dis- 
tributing system  for  fire  purposes  is  a  very 
variable  and  uncertain  one.  Much  depends 
upon  the  class  and  density  of  the  property  to 
be  served.  In  the  case  of  fully-built-up  dis- 
tricts in  a  crowded  city  with  high  buildings, 
offices,  and  warehouses  containing  more  or  less 
inflammable  stock,  a  liberal  allowance  in  main 
room  capacity  must  be  made.  Consideration 
must  be  given  to  the  elevation  of  the  property 
served  with  relation  to  the  level  of  the  service 
reservoir  and  the  pressure  available  at  the 
fire  hydrants  when  discharging  through  the 


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requisite  length  of  hosing.  It  is  also  impor- 
tant to  have  regard  to  the  probable  maximum 
number  of  hydrants  likely  to  be  in  use  at  the 
same  time,  and  the  main  room  provided 
should  be  such  that  the  water  pressures  will  be 
well  maintained  when  the  maximum  number 
of  hydrants  is  in  use.  For  fire  purposes  2^  in. 
diameter  canvas  hosing  is  commonly  employed, 
and  the  loss  of  pressure  due  to  friction  in 
traversing  long  lengths  is  very  marked.  In 
cases  of  large  and  important  buildings, 
especially  where  there  are  a  large  number  of 
occupants,  several  hydrants  will  necessarily  be 
in  use  at  the  same  time,  and  if  a  satisfactory 
supply  is  to  be  afforded,  the  volume  of  the 
main  must  be  increased  to  meet  such  an 
emergency.  In  elevated  situations  where  the 
ordinary  pressures  in  the  mains  is  insufficient 
to  throw  a  jet  of  water  to  the  top  of  a  building, 
the  water  may  usually  be  more  advantageously 
used  through  a  fire  engine,  and  the  capacity 
of  the  mains  should  be  adjusted  to  meet  such 
a  demand.  In  districts  where  the  water  is 
pumped  direct  into  the  distributing  system, 
ample  stand-by  power  should  be  provided,  and 
the  fire  brigade  headquarters  should  be  in 
direct  telephonic  communication  with  the 
pumping  station  so  that  immediate  notification 
of  the  outbreak  of  fire  can  be  transmitted 
thereto  by  the  fire  authorities.  The  spacing 
of  hydrants  will  require  consideration  in 
regard  to  the  properties  to  be  served  ;  thus 
in  busy  town  centres  they  are  often  placed 
from  50  to  100  yards  apart,  and  from  100  to 
150  yards  in  residential  quarters.  Important 
corners  and  cross-roads  will  require  special 
provision  according  to  circumstances. 

CAST-IRON  PIPES  for  water  supply  purposes 
are  usually  made  in  6  ft.  lengths  for  2  in.  and 
2|  in.  diameters,  9  ft.  lengths  for  3  in.  to  10  in. 
diameters,  and  12  ft.  lengths  for  11  in. 
diameter  and  upwards.  The  pipes  should  be 
suitable  for  a  working  pressure  of  about  300  ft. 
head  of  water,  and  should  be  tested  to  a  proof 
strain  of  not  less  than  600  ft.  This  margin 
is  necessary  owing  to  the  varying  pressure  to 
which  the  pipes  are  liable  during  their  life- 
time, such  as  sudden  shocks  and  "  water 


hammer,"  as  may  be  caused  by  turning  the 
water  off  too  suddenly  or  by  air  in  the  pipes 
giving  rise  to  concussion.  For  these  pressures 
the  thicknesses  of  metal  for  2  in.,  3  in.,  and 
4  in.  should  be  f  in.,  for  6  in.  diameter  pipes 
T7^  in.,  for  9  in.  diameter  T9g  in.,  and  for  12  in. 
diameter  f  in. 

Ample  initial  strength  is  also  necessary 
owing  to  the  deterioration  of  the  pipes  after 
being  laid  in  the  ground,  where  they  are 
liable  to  decay  and  oxidation,  thus,  in  the 
course  of  years,  materially  reducing  their 
thickness.  Carbonaceous  matter,  such  as 
cinders,  will,  with  moisture,  eat  into  or  "  pit " 
the  surface  of  the  pipes  laid  in  this  material. 
Very  soft  waters  also  tend  to  cause  deteriora- 
tion by  oxidation  and  incrustation. 

Cast-iron  pipes  should  be  tested  to  the 
pressures  above  named  before  leaving  the 
foundry,  and  should  sustain  the  test  for 
several  minutes,  being  struck  at  the  same 
time  with  a  hammer  so  as  to  produce  a  strong 
vibration.  Specimen  test  bars  and  rods  of 
the  metal  employed  in  the  casting  of  the  pipes 
are  also  very  usually  required  to  be  submitted 
by  the  founders  for  testing  the  transverse  and 
tensile  strengths.  The  straight  pipes  are  cast 
in  sand  moulds  placed  vertically,  and  the 
special  castings  in  close  boxes.  The  thickness 
of  the  metal  should  be  as  uniform  as  possible 
and  the  weights  of  the  pipes  in  the  small 
diameters  should  not  vary  more  than  from 
3  to  4  %.  As  soon  as  the  pipes  have  been 
proved,  and  before  they  are  attacked  by  rust, 
they  should  be  coated  externally  and  internally 
with  a  preservative  composition  such  as  Dr. 
Angus  Smith's  solution.  The  pipes  are  heated 
to  from  300°  to  400°  F.  and  dipped  in  a 
mixture  of  the  composition  approaching 
boiling  point,  thus  forming  a  protective 
coating  on  the  metal. 

Water  mains  should  be  jointed  with  the 
best  soft  blue  pig  lead  and  well  caulked.  The 
joint  should  be  run  in  one  running  so  as  to 
insure  the  whole  joint  being  homogeneous. 
To  prevent  the  lead  passing  into  the  insides 
of  the  pipes,  and  to  economise  the  quantity 
of  lead  used,  the  joint  is  first  caulked  with 


M.S.E. 


545 


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yarn,  then  run  with  lead,  and  afterwards 
set  up. 

On  all  distributing  mains  a  very  important 
fitting  for  the  proper  control  of  the  supply  is 
the  sluice  valve,  of  which  a  large  number  are 
always  required.  These  valves  should  be 
double  faced,  having  two  gun-metal  faces  on 
the  body  of  the  valve  and  two  on  the  valve 
door.  The  valve  spindle  and  nut  are  also  of 
gun-metal,  and  the  gland  and  stuffing-box 
bushed  with  gun-metal.  In  a  district  of  supply 
it  is  important  that  all  the  valves  should  open 
the  same  way,  as  if  some  are  left-handed 
and  others  right-handed  trouble  will  arise 
through  the  valves  being  shut  by  mistake. 
All  valves  should  be  subjected  to  a  hydro- 
static pressure  of  600  ft.  of  water  as  a  test 
before  use,  and  should  be  coated  similar  to 
the  cast-iron  mains  described  above.  Screw- 
down  valves  have  the  advantage  of  shutting 
off  the  main  gradually  and  preventing  con- 
cussions. A  plug-cock  should  not  be  inserted 
in  a  water  main,  as  its  sudden  closing  would 
have  a  very  damaging  effect.  Large  sluice 
valves  on  leading  mains  should  be  provided 
with  indicating  wheel  gearing  to  show  when 
full,  half  open,  or  closed.  It  is  difficult  to 
start  opening  the  door  of  a  large  valve  when 
the  pressure  is  on  one  side  only,  and  to  over- 
come this  trouble  a  small  by-pass  pipe  with 
valve  or  stop-cock  is  provided,  communicating 
with  each  side  of  the  large  valve  for  the  pur- 
pose of  charging  up  the  main  before  opening 
the  larger  valve.  Leading  supply  mains  and 
pumping  mains  should  be  fitted  with  self- 
acting  air  escape  valves  placed  at  every  high 
point  on  the  line  of  main  for  the  escape  of 
air  which  otherwise  accumulates  at  these 
points.  Air  pipes  of  about  f  in.  diameter  con- 
trolled by  a  full-way  cock  are  also  sometimes 
provided  for  releasing  large  quantities  of  air 
when  a  main  is  being  re-charged  after  empty- 
ing. But  little  difficulty  is  experienced  from 
the  accumulation  of  air  in  the  branch  supply 
mains  as  a  rule,  as  the  continual  draught  on 
these  mains  by  the  house  services  allows  of  the 
ready  escape  of  air. 

Other   varieties   of    waterworks    apparatus 


and  fittings  in  general  use  for  the  distri- 
bution of  water  include  different  classes  of 
fire  hydrants,  stand-pipes,  street  watering 
posts,  drilling  apparatus  for  connecting  to 
mains,  tapping  ferrules,  stop-cocks,  bib-taps, 
ball  valves,  bath  and  lavatory  fittings,  flushing 
cisterns  to  w.c.'s,  automatic  flush  tanks,  and 
surface  boxes  for  hydrants,  meters,  &c.  Of 
these  it  may  be  said,  generally,  that  the  best 
types  are  usually  those  which  are  the  simplest 
and  strongest  in  design  and  construction,  and 
that  whilst  a  very  good  idea  of  their  great 
variety  and  design  may  be  gathered  from  an 
inspection  of  the  various  makers'  catalogues, 
experience  in  their  use  under  ordinary  every- 
day conditions  is  the  best  means  of  finding 
out  what  good  points  of  design  are  to  be 
looked  for  and  what  weak  points  are  to  be 
avoided  in  the  selection  of  fittings  of  this 
kind. 

WATEE  SERVICE  PIPES  communicating  be- 
tween the  supply  main  and  the  premises  to 
be  supplied  should  not  be  less  than  f  in. 
internal  diameter,  and  should  be  made  of 
strong  well-galvanised  iron  piping,  or,  in  the 
case  of  a  hard  water,  they  may  safely  be  of 
lead.  The  pipes  must  be  capable  of  with- 
standing an  internal  pressure  of  from  400  ft. 
to  600ft.  head  of  water,  and  should  be  laid 
in  the  ground  with  not  less  than  2  ft.  of  cover 
so  as  to  protect  them  from  damage  by  frost  or 
other  cause.  Every  house  should  be  provided 
with  a  separate  service  pipe,  which  should  be 
connected  with  the  main  by  means  of  a  brass 
screw  stop  ferrule.  A  stop-cock  is  inserted  in 
the  service  pipe  near  the  point  of  entrance  to 
the  premises  supplied  and  on  the  footpath 
wherever  possible.  A  tap  should  also  be 
inserted  in  the  service  pipe  for  the  purpos 
of  completely  emptying  the  pipes  in  cas 
of  frost  or  repairs.  The  drawing  and  stoj 
cocks  should  be  of  the  screw-down  pattern, 
of  the  best  make,  and  be  tested  and  stampec 
by  the  water  authority  before  use.  Al 
soldered  joints  on  lead  pipes  should  be  of 
the  kind  known  as  "plumbers'"  or  "wiped" 
joints. 

Overflow  or  "warning  pipes"  from  cisterns 


546 


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should  be  so  placed  that  the  overflow  may  be 
readily  detected  and  should  not  be  discharged 
into  gutters,  rain-water  pipes,  lead  flats  or 
roofs,  otherwise  a  waste  of  water  may  be 
allowed  to  continue  for  a  considerable  time 
before  being  remedied. 

The  regulations  of  water  authorities  usually 
stipulate  that  w.c.'s.,  urinals,  and  boilers 
should  not  be  supplied  direct  from  the  mains, 
but  from  separate  cisterns.  Water- waste 
preventers  attached  to  w.c.'s  and  urinals 
should  be  capable  of  discharging  2  gallons  of 
water  in  each  complete  flushing  operation  in 
15  seconds.  Such  apparatus  should  be  of  a 
type  approved  by  the  water  authority,  and 
should  be  capable  of  discharging  their  contents 
rapidly  and  with  certainty,  so  as  to  secure  the 
full  benefit  to  be  derived  from  the  effect  of 
the  flush.  A  continuous  running  dribble  of 
water  is  of  no  practical  use  for  flushing  pur- 
poses, and  is  extravagant  and  wasteful.  To 
prevent  waste,  baths  should  be  fitted  with  a 
water-tight  plug  outlet  attached  to  a  chain. 
Ball-taps  for  cisterns  should  be  tested  and 
proved  water-tight  under  a  pressure  of,  say, 
800  Ibs.  to  the  square  inch,  or  according  to 
the  maximum  pressures  likely  to  be  experi- 
enced from  the  mains.  With  proper  regula- 
tions and  adequate  supervision,  water  authori- 
ties are  enabled  to  check  much  waste  and 
misuse  of  water,  such  as  frequently  arise 
from  the  employment  of  inferior  fittings. 

DUAL  SUPPLIES  OF  WATER. — The  difficulties 
of  obtaining  within  a  reasonable  distance 
suitable  supplies  of  pure  water  (in  sufficient 
quantity)  is  yearly  increasing  with  the  growth 
of  population,  and  the  question  is  often  dis- 
cussed as  to  the  advisability  of  introducing 
dual  supplies  of  water,  using  the  purer  sources 
for  all  dietetic  purposes,  and  employing  a  less 
pure  and  cheaper  water  for  street  watering, 
sewer  and  drain  flushing,  and  certain  trade 
purposes.  Several  seaside  towns  in  this 
country  have  installed  plants  and  mains  for 
the  use  of  sea-water  for  municipal  and  other 
purposes,  but  the  results,  speaking  generally, 
can  scarcely  be  considered  a  success,  and  in 
.some  cases  the  system  has  been  abandoned 


altogether.  The  dual  system  of  supply  has 
been  followed  out  to  a  considerable  extent  in 
Paris,  where  the  water  for  domestic  purposes 
is  drawn  from  natural  springs  in  the  chalk  in 
the  basin  of  the  Seine  and  brought  to  the 
city  in  three  closed  aqueducts,  viz.,  the  Dhuis, 
the  Vanne,  and  the  Avre,  and  discharged  into 
covered  service  reservoirs ;  whilst  the  supply 
for  the  streets,  gardens,  stables,  yards,  and 
trade  purposes  is  obtained  from  the  river 
Seine,  the  Marne,  and  the  canal  of  the  Ourcq, 
and  other  sources,  including  artesian  wells. 
The  double  system  is,  however,  not  favourably 
reported  upon. 

The  use  of  two  waters  obviously  involves 
the  laying  down  of  a  double  set  of  distributing 
mains,  thus  greatly  increasing  the  cost  to  the 
water  undertaking,  and  also  greatly  adding  to 
the  complications  of  the  supply  and  increasing 
the  risk  of  mistakes  in  making  connections 
with  the  mains.  When  the  increased  initial 
cost  is  taken  into  consideration,  together  with 
the  annual  expenses  of  the  upkeep  of  two 
supplies,  the  advantage  of  such  a  system  is 
very  doubtful,  unless  some  purely  local  con- 
ditions in  a  given  case  operate  powerfully  in 
its  favour. 

WATER  MAIN  SCRAPING. — Mains  which  have 
become  much  reduced  in  discharging  capacity 
are  sometimes  cleansed  by  introducing  a 
"  scraper "  into  the  main  through  special 
"  hatch-boxes  "  provided  thereon,  and  forcing 
the  same  forward  by  applying  water  pressure 
behind  it.  The  process,  however,  is  frequently 
a  troublesome  operation,  owing  to  the  scraper 
occasionally  becoming  fixed  at  a  bad  joint  or 
bend  in  the  main,  involving,  in  some  cases, 
the  cutting  of  the  main  in  order  to  remove  it. 
Scraping  is  not  often  attempted  on  mains  less 
than  6  in.  in  diameter.  The  average  cost 
of  scraping  appears  to  be  about  '75d.  per 
yard  per  inch  of  diameter  of  main,  including 
wages,  lead,  yarn,  hatch-boxes,  and  scraper, 
but  the  plant  having  once  been  purchased, 
subsequent  scraping  costs  should  be  com- 
paratively small. 

For  further  information  upon  "water 
supply,"  reference  should  also  be  made  to  the 


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following  articles  : — "  Abyssinian  Wells  "  ; 
"Algae  in  Water  Supplies  "  ;  "  Artesian 
Wells  "  ;  "  Bacteriology  of  London  Water 
Supply  "  ;  "  Bore -wells  "  ;  "  Catchwater 
Drain";  "Cholera";  "Dams";  "Effluents"; 
"Filters  (domestic)";  "Filtration  (mecha- 
nical) "  ;  "  Filtration  (through  sand)  "  ;  "  Fish 
Life  in  Streams " ;  "  Frost  (effect  on  water 
fittings)  "  ;  "  Gauging  of  Streams  "  ;  " '  Head ' 
of  Pressure,  loss  of "  ;  "  Hydraulic  Memo- 
randa "  ;  "  Hydrostatic  Head  "  ;  "  Intake  "  ; 
"  Lateral  Water  Filtration  "  ;  "  Leaping 
Weirs  "  ;  "  Local  Government  Board  Require- 
ments (water  supply)  "  ;  "  London  Water 
Supply  "  ;  "Meteorology  "  ;  "Micro-organisms 
in  Water";  "Ozone";  "Pipes,  Cast-iron, 
&c.  "  ;  "  Plumbing  "  ;  "  Pumps  and  Pumping 
Machinery  "  ;  "  Rainfall  "  ;  "  Rain-gauge  "  ; 
"  Rising  Mains  "  ;  "  River  Boards  "  ;  "  Rivers, 
Purification  of  "  ;  "  '  Separator '  for  Rain 
Water  "  ;  "  Siphon  "  ;  "  Stand-pipe  and  Air- 
vessel  "  ;  "  Sterilisation  of  Water  "  ;  "  Suction 
of  Pumps  "  ;  "  Typhoid  "  ;  "  Underground 
Water";  "Valves  (water  supply)";  "  Ven- 
turi  Meter  "  ;  "  Water,  Analysis  of "  ;  "  Water, 
Odours  and  Tastes  "  ;  "  Water  Meters  "  ; 
"  Watershed  "  ;  "  Water,  Sampling  of  "  ; 
"  Water  Supply  (domestic)  ";  "  Water  Supply, 
Royal  Commissions  on  "  ;  "  Wells." 

W.  H.  M. 

Water  Supply,  Royal  Commissions  on. 

— During  the  past  40  years  the  question  of 
water  supply  has  been  under  consideration  by 
a  number  of  Royal  Commissions,  Select 
Committees,  and  others.  The  following  are 
the  dates  of  the  appointment  of  the  various 
Commissions,  and  of  their  reports  : — 1866, 
Royal  Commission  on  Water  Supply  :  Chair- 
man, the  Duke  of  Richmond,  K.G. :  reported 
1869 ;  1868,  Rivers  Pollution  Commission 
(replacing  Commission  issued  in  1865) : 
reported  1874  ;  1872,  reports  by  Mr.  William 
Pole,  "  On  the  Constant  Service  System  of 
Water  Supply";  1879,  Parliamentary  "Re- 
turn showing  the  means  by  which  drinkable 
water  is  supplied  to  every  Urban  Sanitary 
District  in  England  and  Wales " ;  1880, 


Select  Committee  on  London  Water  Supply  ; 
1884-5,  Select  Committee  of  House  of  Lords 
on  Water  Companies  ;  1892,  Royal  Commis- 
sion on  Metropolitan  Water  Supply :  Chair- 
man, Lord  Balfour  of  Burleigh  :  reported 
1893 ;  1897,  Royal  Commission  on  Water 
Supply  within  the  Limits  of  the  Metropolitan 
Water  Companies:  Chairman,  Lord  Llandaff: 
reported  1898  and  1899;  1900,  Select  Com- 
mittee on  Local  Authorities'  Reproductive 
Undertakings.  The  question  has  also  been 
dealt  \vith  on  several  occasions  in  connection 
with  Bills  for  the  water  supply  of  the 
Metropolis  and  other  towns. 

DUKE  OF  RICHMOND'S  COMMISSION,  1866. — 
The  Commissioners  were  directed  to  ascertain 
what  supply  of  unpolluted  and  wholesome 
water  could  be  obtained  by  collection  and 
storage  in  the  high  grounds  of  England  and 
WTales,  either  by  the  aid  of  natural  lakes  or  by 
artificial  reservoirs,  at  a  sufficient  elevation 
for  the  supply  of  the  large  towns,  and  to 
inquire  into  the  existing  water  supply  to  the 
Metropolis.  They  soon  found  that  an  inquiry 
into  the  supply  of  the  provincial  towns  would 
be  one  of  great  magnitude  and  would  pro- 
bably occupy  several  years.  They  therefore 
confined  their  attention  almost  exclusively 
to  the  more  pressing  question  of  the  supply  to 
London.  After  considering  various  proposals 
to  bring  water  from  Wales,  the  Lake  District, 
and  Derbyshire,  they  expressed  the  opinion 
that  the  water  from  the  rivers  Thames  and 
Lea,  together  with  that  obtainable  from  the 
chalk  and  lower  greensand,  would  suffice  to 
supply  any  probable  increase  of  the  Metro- 
politan population  ;  that  there  was  no  evidence 
to  lead  to  the  belief  that  the  water  supplied  by 
the  companies  was  not  generally  good  and 
wholesome ;  that  its  quality  depended  on 
perfect  filtration  ;  and  that  artificial  softening 
did  not  appear  to  be  applicable  to  the  Thamea 
water.  They  expressed  strong  opinions  in 
favour  of  the  system  of  constant  supply,  and 
of  the  control  of  water  undertakings  by  local 
authorities.  Doubts  are  cast  on  the  reliability 
of  gravitation  supplies  to  large  towns  from 
catchment  reservoirs  in  hilly  districts,  and  it 


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is  strongly  recommended  that  no  town  or 
district  should  be  allowed  to  appropriate  a 
source  of  supply  which  naturally  and  geo- 
graphically belongs  to  another.  This  report 
was  issued  on  9th  June,  1869. 

EIVERS  POLLUTION  COMMISSION,  1868. — 
Meanwhile  the  question  of  water  supply  was 
also  being  considered  by  the  Rivers  Pollution 
Commissioners,  Dr.  Edward  Frankland  and 
Mr.  John  Chalmers  Morton,  having  been 
entrusted  to  the  original  Commissioners  in  an 
instruction  dated  7th  July,  1865.  Their  sixth 
and  final  report,  issued  30th  June,  1874, 
deals  exclusively  with  this  question,  and 
constitutes  a  most  valuable  and  exhaustive 
review  both  of  the  existing  supplies  and  of  the 
available  sources  throughout  the  country. 
The  following  is  their  classification  of  waters 
in  order  of  merit : — 

j  1.  Spring  water  (5) .  .          . .  |  Very 
"Wholesome'i  2.  Deep  well  water  (6)       . .  j  palatable. 

[3.  Upland  surface  water  (2)1  Moderately 

14.  Stored  rain  water  (1)     ..[palatable. 
Suspicious  -  5.  Surface  water  from  culti-' 
vated  land  (3).  . 

r 6.  River    water     to    which    Palatable. 
Dangerous  J  sewage  gains  access  (4) 

I?.  Shallow  well  water  (7) 

The  numbers  in  brackets  give  the  positions 
of  the  various  waters  in  order  of  softness.  Ex- 
cessive hardness  is  condemned,  and,  for  waters 
possessing  it,  artificial  softening  is  recom- 
mended. Soft  and  moderately  hard  waters 
are  referred  to  as  equally  wholesome.  The 
Commissioners  state  emphatically  that  no 
river  in  the  United  Kingdom  is  long  enough 
to  secure  the  oxidation  of  sewage  which  may 
be  discharged  into  it,  and  that  no  process 
which  had  been  proposed  down  to  that  time 
could  be  relied  on  to  purify  polluted  water. 
The  protection  afforded  by  sand  filtration 
against  the  propagation  of  epidemic  diseases 
by  water  is  characterised  as  "  feeble."  The 
Commissioners  therefore  recommend  the  early 
abandonment  of  the  Thames  and  Lea  as 
sources  of  water  for  domestic  purposes  in  the 
Metropolis,  and  the  exclusive  use  of  spring 
and  deep-well  waters  from  the  London  basin 


softened  with  lime.  Whenever  circumstances 
compel  the  taking  of  a  water  supply  from  a 
polluted  river,  storage  reservoirs  are  recom- 
mended of  sufficient  capacity  to  render 
unnecessary  the  intake  of  water  during  floods. 
The  water  supplies  of  the  Royal  residences  are 
specially  reported  on. 

ROYAL  COMMISSION  ON  METROPOLITAN  WATER 
SUPPLY,  1892. — Lord  Balfour's  Commission 
reversed  the  finding  of  its  predecessors 
recommending  the  abandonment  of  the 
Thames  and  Lea,  and  expressed  a  strong 
opinion  that  the  water  supplied  to  London 
was  "  of  a  very  high  standard  of  excellence 
and  of  purity,  and  .  .  .  suitable  in  quality 
for  all  household  purposes."  With  regard  to 
the  prejudice  which  exists  against  these 
waters  on  the  ground  of  sewage  pollution 
they  observe  :  "  We  do  not  believe  that  any 
danger  exists  of  the  spread  of  disease  by  the 
use  of  this  water,  provided  that  there  is 
adequate  storage,  and  that  the  water  is 
sufficiently  filtered  before  delivery  to  the 
consumers."  They  were  also  of  opinion  that 
a  sufficient  supply  for  the  wants  of  the 
Metropolis  might  be  found  within  the  valleys 
of  the  Thames  and  Lea  for  a  long  time  to 
come.  They  recommended  the  exercise  of 
all  possible  vigilance  to  prevent  unnecessary 
contamination  of  these  rivers  and  their  tribu- 
taries, the  construction  of  adequate  storage 
reservoirs,  and  the  keeping  of  accurate 
observations  on  the  effect  of  pumping  from 
the  chalk  upon  the  water  levels  in  the  wells  in 
that  formation. 

ROYAL  COMMISSION  ON  WATER  SUPPLY 
WITHIN  THE  LIMITS  OF  THE  METROPOLITAN 
WATER  COMPANIES,  1897. — The  first  report  of 
Lord  Llandaff's  Commission  dealt  exclusively 
with  the  question  of  intercommunication 
between  the  systems  of  the  different  Metro- 
politan water  companies.  Their  second  and 
final  report  was  of  a  more  general  character. 
In  the  latter  they  expressed  a  general  ap- 
proval of  the  findings  of  Lord  Balfour's 
Commission  as  regards  the  suitability  and 
adequacy  of  the  existing  sources  of  supply  to 
London.  They  examined  the  proposals 


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brought  forward  by  the  London  County 
Council  for  obtaining  a  supply  from  Wales 
and  dismissed  it  as  costly  and  unnecessary. 


minute  vegetable  and  animal  life  in  the 
water  at  its  source.  These  periodic  odours 
and  tastes  are  to  be  distinguished  from  those 


They  expressed  a  strong  opinion  in  favour  of     which    constantly   obtain    in    a    water,    and 
constituting   a   public    authority    to   acquire     which  may  be  due  to  its  geological  source  or 
and  manage  the  undertakings  of  the  London 
water  companies,  and  outlined  the  constitu- 
tion   of    the    suggested    authority    and    the 
powers  which  should  be  entrusted  to  it. 

A.  J.  M. 

Water  Supplies  (Odours  and  Tastes  in). 

— The  causes  of  odours  and  tastes  in  water 
supplies  and  the  methods  of  prevention  have 


FIG.  1. — Si/Hiim,  magnified  500  dia.  Free- 
swimming  colony  of  from  10  to  50  biciliated 
individuals. 


not  generally  received  the  full  amount  of 
attention  the  importance  of  the  subject 
deserves.  Many  engineers  in  charge  of  the 
working  of  water  supply  systems  are  familiar 
with  complaints  from  consumers  in  regard  to 
smells  from  the  water  supplied,  especially 
when  heated,  or  in  respect  of  unusual  tastes 
occasionally  noticeable  in  the  same.  Such 
complaints  often  occur  at  intermittent  periods, 
and,  in  many  cases,  no  proper  explanation 
has  been  forthcoming  owing  to  the  difficulty 
of  precisely  identifying  the  true  cause.  Of 
recent  years  much  light  has  been  thrown 
upon  the  subject  by  a  more  systematic  study 
of  the  microscopy  of  drinking  waters,  and  it 
is  now  known  that  such  odours  and  tastes  are 
very  frequently  due  to  the  periodic  growth  of 


FIG.  2. —  Uroglena,  magnified  250  dia. 


Uroylena,  showing  a  single  cell 
magnified  1,000  dia. 

the  dissolved  mineral  constituents  it  contains— 
for  example,  as  in  the  case  of  brackish,  chaly- 
beate or  mineral  waters,  such  as  those  of 
Bath,  Harrogate,  and  others.  Chemically 
pure  water  is  free  from  both  odour  and  taste, 
but  is  not  met  with  in  nature.  Many  under- 
ground waters  have  either  a  saline  or  inky 
taste,  and  some  a  decidedly  sulphurous  odour, 
and  gases  may  be  given  off  in  very  perceptible 
quantities.  Water  from  swampy  ground  or 
from  thickly  wooded  catchment  areas  may  yield 
a  somewhat  mould}7,  woody,  and  unpleasant 
taste.  Nearly  all  waters  have  some  odour, 
though  oftentimes  it  is  too  faint  to  be 
observed  by  the  ordinary  consumer.  Roughly 
speaking,  such  odours  may  be  due  to  the 
presence  of  organic  matter  other  than  living 
organisms,  to  the  decomposition  of  organic 


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matter,  or  to  the  growth  of  living  organisms, 
both  animal  and  vegetable,  in  the  water. 

Odours  derived  from  organic  matter  other 
than  living  organisms  are  in  general  of  a 
vegetable  origin,  and  are  variously  described 
by  different  observers  as  marshy,  peaty, 
straw-like,  woody,  and  such  like.  Heating 
the  water  generally  intensifies  the  smell. 

When  vegetable  or  animal  matter  in  water 
begins  to  decay  very  unpleasant  odours  are 
sometimes  produced.  These  are  commonly 
described  as  mouldy,  fishy,  musty,  and  so 
forth. 

Of  all  the  odours  occurring  in  water  supplies 
the  most  important  are  those  due  to  the 
development  of  living  organisms  owing  to  their 
nature  being  oftentimes  very  offensive,  and 
also  to  the  fact  that  they  frequently  seriously 
affect  large  quantities  of  water,  rendering  it 
quite  unsuited  for  public  supply.  In  the 
writer's  experience  the  rapid  development  of 
the  diatom  asterionella  in  a  large  open  storage 
reservoir,  in  which  a  mixed  supply  of  spring 
and  underground  water  was  unavoidably 
stored,  rendered  a  large  body  of  otherwise 
excellent  water  totally  unfit  for  public  supply, 
and  also  proved  to  be  so  prolific  that  the 
surface  of  sand  filter  beds  became  effectually 
blocked  with  the  diatoms  in  the  course  of 
about  3  days'  working.  The  surface  film  on 
the  sand  could  then  be  rolled  off  like  a  carpet. 


FIG.  3. — Vvlvox,  magnified  80  dia. 

Like  most  animals,  different  kinds  of  living 
organisms  in  water  each  have  a  natural 
characteristic  smell,  so  much  so,  that  experi- 
enced observers  are  able  at  once  to  identify 
the  organism  by  the  smell  of  the  water.  In 


a  great  many  cases,  and  perhaps  in  all,  the 
odour  is  due  to  the  existence  within  the  cells 
of  the  organism  of  minute  oil  globules,  or 
compounds  analogous  to  the  essential  oils, 
which  are  to  be  distinctly  observed  under 


FIG.  4. — Rivnlaria,  magnified  about  500  dia. 

suitable  powers  of  the  microscope.  The  oils 
are  produced  during  the  growth  of  the 
organism,  are  generally  most  numerous  in 
mature  forms,  and  oftentimes  particularly  so 
immediately  preceding  sporulation  or  encyst- 
ment.  The  odour  is  intensified  by  any  process 


FIG.  o.—Anabcena,  magnified  500  dia. 

tending  to  break  up  the  organism,  such  as 
mechanical  agitation,  increased  pressure, 
pumping,  or  heating  the  water,  as  the  ';  oils  " 
thereby  become  liberated  and  dispersed 
throughout  the  water.  This  natural  odour 
of  the  oil  globules  of  the  organism,  the 


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production  of  which  represents  a  kind  of  stor- 
ing up  of  energy,  is  to  be  clearly  distinguished 
from  the  disagreeable  odours  produced  by  their 
decomposition.  The  organisms  develop  most 
luxuriantly  in  quiet  reservoirs,  ponds,  or  back- 
waters, and  are  oftentimes  attached  in  great 
quantities  to  the  vegetation  contained  in  the 
reservoir. 

The  odours  commonly  met  with  in  water 
supplies  are  very  variable  and  are  difficult  to 
describe.  A  few  of  those  which  are  fairly 
well  denned  together  with  the  organism 
causing  them  are  : — 


Description  of  Natural  Odour. 

Organism  Causing  the  Odour. 

Ripe    cucumber     odour    with 

bitter  taste 

Synura. 

Fishy  and  oily  odour 

Uroglena. 

Fishy 

Volvox. 

Mouldy   and   like  freshly   cut 

grass 

Bivularia. 

Mouldy      and     grassy  —  like 

nasturtiums 

Anabeena. 

First    aromatic  —  geraniums  — 

and  with  larger  numbers  of 

organisms  strongly  fishy    .  . 

Asterionella. 

A  water  may  be  odourless  although  contain- 
ing large  numbers  of  organisms.  Most  of  the 
organisms  produce  oil  at  some  stage  of  their 
growth,  but  the  oils  in  some  cases  may  be 
odourless.  The  aromatic  odours  are  mostly 


FIG.  6. — Asterionella,  magnified 
500  dia. 

due  to  the  diatomaceae,  the  strongest  smell 
being  that  derived  from  asterionella  above 
referred  to.  Uroglena  gives  a  very  unpleasant 
odour ;  it  is  quite  common,  and  water  impreg- 
nated with  this  organism  smells  fishy  and 
something  like  cod-liver  oil.  The  fishy  odours 


are  generally  produced  by  organisms  belonging 
to  the  animal  kingdom. 

The  question  naturally  arises  as  to  whether 
the  drinking  of  water  containing  large  quan- 
tities of  living  organisms  is  injurious  to  health. 
This  is  a  matter  which  cannot  be  very  defi- 
nitely answered,  but  from  present  information 
it  is  generally  believed  that  such  organisms 
are  not  injurious.  At  the  same  time,  how- 
ever, it  appears  more  than  probable  that  a 
change  from  the  drinking  of  pure  water  to 
the  use  of  one  highly  charged  with  micro- 
scopic growths  may  at  least  give  rise  to  tem- 
porary intestinal  disorders,  especially  in  the 
case  of  invalids  and  young  children. 

The  question  of  the  removal  of  micro- 
organisms from  large  quantities  of  drinking 
waters  is  a  matter  of  some  difficulty,  and,  in 
many  cases,  of  almost  impossibility  except  by 
the  slow  operation  of  the  ordinary  processes 
of  nature.  Ordinary  sand  filtration  is  not 
always  successful,  as  the  odour-producing 
substances  may  sometimes  pass  through  the 
filters  unchanged.  Also,  large  quantities  of 
microscopic  material  rapidly  accumulates  by 
deposit  and  by  increased  growth  upon  the 
surface  of  the  filter  beds,  causing  prohibitive 
expense  in  cleansing  the  same.  The  best 
course  to  adopt,  wherever  possible,  is  to  take 
steps  to  prevent  the  development  of  such 
growths  by  avoiding  the  conditions  which 
have  proved  favourable  to  the  multiplication 
of  the  organisms.  For  example,  in  the  writer's 
experience,  the  open  storage  of  deep  well  or 
underground  water  together  with  surface  or 
spring  waters  produces  at  certain  periods 
very  troublesome  growths  of  asterionella 
which  may  seriously  interrupt  the  entire 
town  supply.  This  has  been  completely  over- 
come by  the  installation  of  mechanical  filters 
to  deal  direct  with  the  underground  water 
(which,  in  the  case  in  point,  contains  iron  in 
solution),  and  storing  the  top  waters  only  in 
open  reservoirs  pending  sand  filtration  in  the 
ordinary  way.  W.  H.  M. 


Water- Wheels. — Water-wheels  are  seldom 
installed  now,  but  so  many  remain  in  use  and 


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they  are  so  well  suited  for  driving  pumps, 
without  the  intervention  of  gearing,  that  the 
main  features  of  the  various  types  may  be 
shortly  considered.  These  may  he  broadly 
classed  as  "undershot,"  "overshot,"  and 
"  breast" — terms  derived  from  the  manner  in 
which  the  water  is  applied  to  them.  The 
undershot  w?heel  is  driven  by  the  impulse  of 
the  water  upon  "  floats  "  or  paddles  radiating 
from  its  circumference.  Such  wheels  \vere 
originally  placed  in  mid-stream  with  their 
floats  dipping  into  it.  An  improvement  con- 
sisted in  damming  the  stream  and  providing  a 
sluice  at  the  bottom,  through  which  the  water 
issued  and  impinged  upon  the  floats  with  a 
velocity  proportionate  to  the  "  head  "  behind 
the  dam.  By  setting  the  floats  at  a  tangent 
to  the  circumference  better  results  were 
obtained,  but  the  greatest  advance  was  made 
by  Poncelet,  who  curved  the  floats  and  wheel- 
race  and  thereby  realised  about  60  %  of  the 
theoretical  power  of  the  waterfall,  and  effi- 
ciency of  twice  that  of  the  common  undershot 
wheel.  The  "Poncelet"  (which  is  strictly 
speaking  a  kind  of  "impulse"  turbine)  is  a 
very  suitable  water-wheel  for  falls  up  to  about 
6  ft.  In  the  overshot  wheel  the  water  is 
carried  over  the  top  by  a  "  pentrough  "  from 
the  open  end  of  which  it  discharges  into 
buckets  placed  around  the  circumference  of 
the  wheel.  An  overshot  wheel  thus  acts 
entirely  by  gravity,  the  unbalanced  \veight  of 
the  water  in  the  descending  buckets  causing 
a  preponderance  on  that  side  of  the  wheel  and 
consequently  its  rotation.  The  chief  sources 
of  loss  are  due  to  the  fact  that  the  wheel,  in 
order  to  clear  the  bottom  of  the  pentrough  and 
back-water  in  the  tail  race,  must  be  less  in 
diameter  than  the  height  of  the  fall,  and  also 
that  the  buckets  are  emptied  before  they 
have  completed  their  descent.  The  highest 
efficiency  obtainable  is  about  70  %. 

In  the  "  pitchback  "  wheel  the  diameter 
exceeds  the  height  of  the  fall,  and  the  pen- 
trough,  instead  of  being  taken  over  the 
wheel,  discharges  the  water  on  to  its  shoulder; 
the  leverage  at  the  commencement  is,  there- 
fore, more  advantageous  than  with  an 


overshot  wheel,  but  the  slight  gain  involves  a 
larger  and  more  expensive  wheel.  With  the 
old  form  of  breast  wheel  the  water  acts 
both  by  impulse  and  gravity.  In  construc- 
tion it  differs  from  the  undershot  in  not 
having  \vide  open  spaces  between  the  floats 
on  the  circumference  of  the  framing ;  in  fact, 
the  floats  serve  as  buckets,  the  water  being 
retained  in  them  by  the  w^alls  between 
which  the  wheel  works  and  the  concave 
"  breasting "  (of  brickwork  or  masonry) 
embracing  a  portion  of  the  periphery,  until  its 
escape  into  the  tail  race  is  permitted.  It  is 
now  usual  to  fit  buckets  similar  to  those  of  an 
overshot  wheel.  The  "hatch"  or  sluice  by 
wrhich  the  supply  is  regulated  is  now  so 
arranged  that  the  water  flows  over  instead  of 
under  it  as  formerly;  by  this  means  every 
inch  of  "  head  "  is  utilised,  and  the  water,  act- 
ing entirely  by  gravity,  is  used  to  better 
advantage. 

Breast  wheels  may  be  classed  as  "high" 
or  "low,"  according  to  wrhether  the  water 
is  applied  above  or  belov;  the  horizontal 
centre  line  of  the  wheel.  Until  the  advent  of 
the  turbine,  the  breast  wheel  was  the  most 
efficient  for  utilising  falls  of  moderate  head. 
These  conditions  so  often  exist  in  this  country 
that  breast  wheels  have  received  a  great  deal 
of  attention  and  have  been  brought  to  a  high 
degree  of  efficiency.  This  varies  from  55  % 
for  the  low  breast  up  to  70  %,  and  in  some 
cases  75  °/0,  for  the  high  breast.  The  large 
size  of  a  water-wheel  in  relation  to  the  power 
developed  renders  the  first  cost  high  ;  this  is 
also  increased  by  the  massive  gearing  neces- 
sary to  impart  the  requisite  speed  to  the 
machinery.  Further  they  are  seriously 
affected  by  floods,  as  the  floats  or  buckets 
have  to  be  driven  through  the  back-water. 
(See  "  WATER  POWER,"  "  TURBINES.") 

E.  L.  B. 

Webster's  Process  of  Sewage  Purifica- 
tion by  "  Electrolysis.— The  precipitation 
of  sewage  by  "  electrolysis  "  has  been  success- 
fully tried  at  Crossness,  near  the  southern  out- 
fall of  the  Metropolitan  sewage.  By  this  system 


553 


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ENCYCLOPAEDIA   OF 


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the  sewage  is  passed  through  channels  between 
iron  electrodes,  whereby  the  chlorides  are 
electrolysed  and  the  sewage  is  deodorised  by 
the  chlorine  and  oxygen  set  free  at  the  positive 
pole  of  the  electrode,  and  the  iron  salts  formed 
also  assist  in  the  purification  of  the  sewage. 
It  appears  that  the  treatment  produces  a 
reduction  in  the  oxidable  matter  in  the  sewage 
of  from  60  to  80  %.  A  risk  of  a  direct  process 
such  as  electrolysis  would  seem  to  be  that  the 
effective  action  may  be  only  local,  and  that 
sewage  may  pass  between  the  electrodes 
without  much  purification. 

Wells  and   Well    Supplies.— Wells    of 

different  kinds  are  named  according  to  their 
depth,  size,  mode  of  sinking,  and  so  forth,  e.g., 
shallow  wells,  subsoil  wells,  dip-wells  and 
draw-wells,  deep  wells,  Abyssinian  or  tube 
wells,  and  artesian  wells  or  borings. 

SHALLOW  WELLS  are  those  entirely  contained 
in  a  superficial  bed  of  gravel  or  sand,  and  fed 
by  land  soakage  and  surface  springs,  which 
may  fail  in  dry  weather.  The  water  is  either 
dipped,  raised  by  hand  or  by  a  suction  pump. 
In  the  sixth  report  of  the  Eivers  Pollution 
Commissioners,  the  shallow  wells  examined 
were  under  50  ft.  in  depth,  and  the  deep  wells 
generally  over  100  ft.  deep;  nevertheless,  a 
well  completely  contained  in  a  superficial 
stratum  of  sand  or  gravel  may  be  actually 
deeper  than  a  so-called  "deep"  well,  which 
has  pierced  a  regular  geological  stratum  such 
as  the  chalk  or  new  red  sandstone.  Deep  well 
water  is  generally  looked  upon  as  one  of  the 
purest  waters  obtainable  for  public  supply, 
except  when  containing  mineral  salts  in 
objectionable  quantities.  The  salts  present 
will  depend  more  upon  the  strata  through 
which  the  water  has  percolated  than  upon  its 
original  source.  Deep  well  waters  often  con- 
tain a  large  amount  of  iron  and  are  frequently 
somewhat  deficient  in  aeration.  In  such  a 
case  the  water  should  be  discharged  in  a 
cascade  over  a  bell-mouth  pipe,  or  down  a 
series  of  steps  in  order  to  effect  a  thorough 
aeration,  and  so  hasten  the  precipitation  of 
the  iron.  It  may  also  be  treated  for  the 


removal  of  iron  by  means  of  the  Candy 
oxidising  pressure  filters  (see  "  MECHANICAL 
FILTRATION  ").  Excellent  deep  well  supplies 
have  been  obtained  from  the  new  red  sand- 
stone by  Birmingham,  Liverpool,  and  many 
other  towns,  and  from  the  chalk  by  Brighton, 
Margate,  Eastbourne,  and  other  places. 
Hastings  obtains  its  deep  well  supplies  from 
the  Ashdown  Sands,  the  water  there  being 
highly  impregnated  with  iron. 

The  chalk  supplies  are  obtained  by  large 
wells  some  10  or  12  ft.  in  diameter  sunk  in 
the  chalk,  and  having  "  adits  "  or  headings 
driven  in  different  directions  from  the  base  of 
the  well  so  as  to  intercept  the  water-bearing 
fissures  and  create  a  large  reserve  of  under- 
ground storage. 

DEEP  BORINGS  in  the  new  red  sandstone, 
Ashdown  sands,  and  other  strata  are  fre- 
quently drilled  through  the  rock  to  consider- 
able depths  by  special  boring  machines,  and 
are  lined  as  sunk  with  lengths  of  steel  tubing 
screwed  together,  the  lower  lengths  of  tubing 
having  a  large  number  of  perforations  for  the 
admission  of  the  water.  Such  wells  are  bored 
to  almost  any  requisite  depth,  from  3  in.  up  to 
30  in.  in  diameter,  and  the  water  is  often 
tapped  under  an  artesian  head,  as,  for  example, 
is  the  case  with  many  borings  within  the 
London  basin. 

When  a  deep  boring  is  sunk  through  the 
London  clay  to  the  lower  Tertiary  sands  or 
deeper  into  the  underlying  chalk,  the  water 
rises  in  the  borehole,  and,  in  some  cases,  even 
reaches  the  surface  and  overflows.  The 
conditions  under  which  such  a  circumstance 
arises  will  be  apparent  from  an  examination 
of  Fig.  ] ,  which  is  a  geological  section  across 
the  Thames  basin,  north  to  south,  from  the 
Chiltern  Hills  to  the  North  Downs  and  Weald 
of  Kent.  If  the  water  is  tapped  in  low-lying 
ground  as  at  A  in  the  figure,  which  is  in  the 
hollow  of  the  London  basin,  it  is  necessarily 
much  below  the  level  of  the  outcrop  of  the 
water-bearing  strata  at  B  and  C,  and  the  water 
will  consequently  be  forced  up  the  boring  to 
its  rest-level  approximating  to  that  in  the 
surrounding  strata.  In  some  districts  the 


554 


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MUNICIPAL  AND   SANITARY  ENGINEERING. 


WEL 


pressure  of  the  underground  water  is  such  that 
it  not  only  rises  and  overflows  at  the  surface, 
but  is  forced  into  the  air  many  feet,  thus 
producing  what  is  termed  an  "  Artesian  well" 
(see  "ARTESIAN  WELLS").  One  of  the  most 
interesting  of  such  wells  is  that  at  Bourn, 
in  Lincolnshire,  which  supplies  the  town  of 
Spalding.  It  was  bored  by  C.  Isler  &  Co., 
Southwark,  in  the  Oolitic  beds,  and  at  the  depth 
of  100  ft.  it  yielded  a  flow  of  1,800  gallons  per 
minute  at  a'pressure  of  lOlbs.to  the  square  inch, 
reaching  the  ground  surface  with  a  rush.  On 
sinking  a  further  34  ft.  the  flow  was  increased 
to  3,480  gallons  per  minute.  In  another  boring 
(6  in.  in  diameter)  by  the  same  firm  at 


lation  of  fresh  supplies,  to  gradually  deplete 
the  storage  of  subterranean  water. 

In  England  the  most  favourable  strata  for 
deep  wells  are  the  chalk,  oolites,  new  red 
sandstone,  and  the  lower  greensand.  The 
yield  will  depend  on  the  extent  of  the  under- 
ground reservoir,  the  area  of  the  outcrop  of 
the  water-bearing  strata,  its  porosity  or  degree 
to  which  it  admits  of  percolation  of  rainfall, 
and  other  considerations  (see  "  UNDERGROUND 
WATER"). 

SHALLOW  WELLS. — In  rural  districts  good 
water  may  oftentimes  be  obtained  from  a 
shallow  well,  provided  the  requisite  precau- 
tions are  taken  in  the  construction  to  insure 


X^B-       C^°  iX 


CV# 


cv^ 


FIG.  1. — Geological  Section  across  the  Thames  Basin  from  the  Chiltern  Hills  to  the  Weald  of  Kent. 


Keighley,  Yorkshire,  sunk  in  the  upper  beds 
of  the  millstone  grit,  a  supply  of  15,000  gallons 
per  hour  was  tapped,  and  the  water  rose  to  a 
height  of  40  ft.  above  the  surface. 

In  the  London  basin  the 
general  rule  is  that  in  borings 
400  ft.  deep  the  water  level  is 
100  to  200  ft.  from  the  surface. 

The  fountains  in  Trafalgar 
Square  are  supplied  from  an 
artesian  well  penetrating  to  a 
depth  of  about  390  ft.  below  the 
surface,  and  numerous  private 
supplies  to  breweries  and  other 
manufacturing  establishments, 
as  well  as  part  of  the  supplies  of 
some  of  the  London  water  under- 
takings, are  derived  from  the 
chalk  underlying  London.  The 


protection  from  contamination  and  surface 
washings.  The  sides  of  such  a  well  should  be 
lined  with  brickwork  set  in  cement,  outside  of 


Impervious  Paving 


Puddle  or 
Concrete 


FIG.  2.— Section  showing  Top  Part  of  Shallow  Well. 


efi'ect  of  continually  drawing  large  supplies 
from  borings  of  this  description  is  to  lower 
the  general  level  of  underground  water,  and, 
unless  adequately  fed  by  the  downward  perco- 


which  should  be  a  thickness  of  impervious  clay 
puddle  extending  downwards  for  about  two- 
thirds  of  the  depth  of  the  well,  or  as  circum- 
stances may  require.  The  brick  lining  should 


555 


WEL 


WHI 


also  be  carried  up  2  or  3  ft.  above  the 
adjoining  ground  surface  and  fitted  with  a 
good  cover,  to  prevent  rubbish,  animals,  &c., 
from  falling  into  the  well.  The  ground  around 
the  well  should  also  be  paved  with  some 
impervious  paving,  as  asphalte  or  concrete, 
and  sloped  away  as  shown  in  Fig.  2,  so  that 
no  top  soakage  may  gain  access.  For  drawing 
the  water  a  pump  is  much  to  be  preferred 
to  the  old-fashioned  bucket  and  windlass,  as 
the  well  can  be  kept  permanently  covered 


Well 


Ground  swrfa 


SO- 3 4^-— ^&|_   PLAN 


Circle  shewing  extent  of  influence  of 
pumping  for  a  depression-  AB  in,  the 
well 

FlG.  3. 

and  the  water  is  not  disturbed  and  exposed  to 
pollution  to  the  same  extent.  In  spite  of 
precautions,  however,  all  wells  may  at  times 
become  polluted  if  situate  near  cesspools  or 
other  accumulations  of  filth.  Much  depends 
on  the  direction  of  flow  of  the  ground  water.  If 
thisbecomes  polluted  by  leakage  from  a  defective 
cesspool  or  drain  and  the  ground  water  flows 
in  the  direction  of  a  well,  the  water  therein 
will  naturally  acquire  dangerous  properties, 
and  in  this  way  the  germs  of  typhoid,  for 
example,  may  be  conveyed  from  cesspool  to 
well,  and  the  disease  thus  rapidly  spread 
throughout  the  area  supplied  from  this  source. 


Numerous  cases  of  this  kind  have  been  met 
with  in  practice.  The  risks  of  such  pollution 
are  always  greatest  after  heavy  rainfalls,  when 
the  level  of  the  ground  water  is  high  and  more 
likely  to  be  brought  into  immediate  contact 
with  leakage  from  cesspools,  &c. 

Pumping  from  a  well  draws  down  the  level 
of  the  underground  water  around  the  site  of 
the  well  somewhat  in  the  manner  illustrated 
in  Fig.  3,  where  A  B  is  assumed  to  be 
the  extent  of  the  depression  from  "rest  level." 
This  influence  is  communicated  in  all  direc- 
tions from  the  site,  and  the  slope  of  the  lines 
of  depression  B  C  E  and  B  D  E  will  depend 
largely  upon  the  porosity  or  permeability  of 
the  surrounding  strata.  The  distances  from 
which  underground  water  is  thus  drawn  often 
extend  to  many  miles  radius,  and  are  expressed 
in  terms  of  the  depression.  In  chalk  the  dis- 
tance may  amount  to  57  times  the  depression 
of  the  water  level  in  the  well,  and  in  coarse 
gravel  the  distance  affected  is  as  much  as  160 
times  the  depression.  Very  much  will  depend, 
however,  on  the  nature  of  the  strata  in  any 
individual  case.  (For  further  information  sec 
also  articles  "ARTESIAN  WELLS,"  "ABYSSINIAN 
WELLS,"  "WATER  SUPPLY,"  and  "UNDER- 
GROUND WATER.")  W.  H.  M. 

White  Lead. — This  is  hydrocarbonate  of 
lead  made  by  exposing  metallic  lead  to  the 
fumes  of  carbonic  acid  gas  and  acetic  acid. 
The  ancient  "  stack  "  process  is  usually  recog- 
nised as  yielding  the  best  results,  notwith- 
standing all  attempts  at  improvement.  The 
metallic  lead  is  cast  in  the  form  of  wickets  not 
unlike  a  miniature  gate  in  shape.  Pots  con- 
taining acetic  acid  are  arranged  close  together 
on  a  platform  covered  with  spent  tan,  and 
these  wickets  are  strewn  indiscriminately  upon 
the  pots.  A  second  platform  is  built  imme- 
diately above,  and  upon  it  the  pots  and  wickets 
are  placed,  and  so  on  until  the  top  of  the 
chamber  is  reached.  The  chamber  is  then 
closed  in  so  that  the  fumes  cannot  escape,  and 
after  a  period  of  three  months  the  metal 
wickets  are  converted  into  a  white  lead.  These 
are  then  taken  out,  passed  through  mills, 


556 


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MUNICIPAL  AND   SANITAEY  ENGINEERING. 


WIN 


washed,  ground  nnd  dried,  and  finally  again 
ground  in  oil,  when  the  white  lead  is  ready  for 
painters'  use.  English  white  lead  is  probably 
the  best  in  the  world.  There  is  a  good  deal 
of  white  lead  made  abroad  coarsely  ground  and 
brought  to  this  country  and  ground  here  and 
then  sold  as  "  English  manufacture."  In 
specifying  white  lead  it  is  advisable,  therefore, 
to  state  that  it  is  to  be  "English  corroded." 
Adulterated  white  lead  is  either  marked 
"  reduced,"  or  No.  1,  No.  2,  &c.  Pure  lead  is 
always  marked  "  Genuine,"  and  if  contained 
in  an  unbroken  package  one  may  be  reason- 
ably sure  the  contents  are  as  represented. 

Whittaker     &     Bryant     Filter.— The 

Whittaker  &  Bryant  "  thermal  aerobic 
filter  "  was  introduced  at  Accrington  in  1898. 
Septic  tank  liquor  was  distributed  over  a 
filter  consisting  of  1  ffc.  of  limestone  chippings 
at  the  top,  6  ft.  of  gas  coke,  and  2  ft.  broken 
stone  by  means  of  a  revolving  distributor.  A 
distinctive  feature  of  the  system  consists  in 
the  use  of  a  steam  pipe  in  the  delivery  of  the 
sprinkler.  A  small  jet  of  steam  is  injected 
into  the  sewage  as  it  arrives  at  the  distributor 
with  the  object  of  raising  the  temperature  of 
the  sewage  and  filter  generally  to  a  suitable 
degree  for  rapid  bacterial  action.  The  arti- 
ficial heat  is  also  intended  to  induce  air  currents 
through  the  filter  and  thus  create  better 
aeration.  Filters  of  this  description  have  also 
been  successfully  tried  at  Leeds. 

Wind  Force. — The  force  of  the  wind  is 
usually  estimated  without  instruments  accord- 
ing to  Admiral  Beaufort's  scale.  This  scale, 
with  the  generally  accepted  equivalent  velocity 
in  miles  per  hour,  is  as  follows  : — 

Scale.  Description  of  Wind.     Equivalent  Velocity. 

0  Calm  ...       0  miles  per  hour 

1  Light  air    .          1 — 3     ,,          .„ 

2  Light  breeze        4 — 7     ,,  ,, 

3  Gentle      „         8—12     „ 

4  Moderate  „      13 — 18     ,,  „ 

5  Fresh        „       19—24     „ 

6  Strong      „      25—31     „ 

7  Moderate  gale  32 — 38     „          ,, 


Scale.   Description  of  Wind.       Equivalent  Velocity. 

8  Fresh   gale      39 — 46  miles  per  hour 

9  Strong    ,,         47—54     „ 

10  Whole     „         55—63     „ 

11  Storm  64—75     „ 

12  Hurricane     above  75     „  ,, 

The  best  instrument  for  recording  the  force  of 
the  wind  is  Dines'  Pressure-tube  Anemometer. 
In  this  advantage  is  taken  of  the  fact  that  the 
air,  in  blowing  over  an  obstacle,  produces 
small  differences  of  pressure  on  various  sides 
of  the  obstacle,  which  are  capable  of  exact 
measurement,  and  afford  information  of  the 
velocity  of  the  wind.  The  "  head"  consists  of 
a  piece  of  tube  open  at  one  end,  which  end  is 
kept  facing  the  wind  by  a  vane.  The  wind 
blowing  into  the  tube  produces  an  excess  of 
pressure  within  it.  There  is  also  a  piece  of 
tube  placed  vertically  and  pierced  by  a  ring  of 
small  holes.  The  wind  blowing  over  these 
holes  produces  a  slight  decrease  of  pressure 
inside.  These  differences  of  pressure  are  com- 
municated by  composition  tu-bing,  which  may 
be  of  any  length,  to  the  place  where  the 
recording  part  of  the  instrument  is  placed. 
The  registration  is  produced  by  means  of  a 
bell-shaped  vessel  which  floats  inverted  in 
water  in  a  closed  chamber.  The  pressure  tube, 
i.e.,  the  tube  coming  from  the  "head"  in 
which  there  is  an  excess  of  pressure,  opens 
above  the  water-level  inside  the  inverted 
floating  vessel,  and  the  other  tube,  i.e.,  that 
in  which  there  is  a  decrease  of  pressure,  com- 
municates with  the  sealed  chamber.  Very 
trifling  differences  of  pressure  are  sufficient  to 
alter  the  level  at  which  the  inverted  vessel 
floats,  and  a  pen  rigidly  attached  to  the  vessel 
makes  a  continuous  record  on  a  clock  drum  in 
the  usual  way.  The  charts  are  arranged  to 
give  both  the  wind  velocity  in  miles  per  hour 
and  the  wind  pressure  in  pounds  per  square 
foot.  In  the  Osier  Anemometer  the  pressure 
of  the  wind  in  pounds  per  square  foot  is 
recorded  by  its  action  on  a  circular  plate 
mounted  on  spiral  springs  and  kept  facing  the 
wind  by  the  vane.  During  gales  the  wind 
attains  a  high  velocity,  the  greatest  recorded 
in  1  hour  being  between  77  and  80  miles  at 


557  . 


WIN 


ENCYCLOPAEDIA   OF 


ZIN 


Eleetwood.  In  gusts,  however,  the  velocity  of 
the  wind  may  momentarily  exceed  the  rate  of 
100  miles  an  hour.  W.  M. 

Wind  Motors.  —Although  the  familiar 
four-armed  windmill  is  becoming  a  thing  of 
the  past,  employment  of  the  wind  as  a  motive 
power  for  pumping,  &c.,  is  extending.  At 
exposed  sites  in  this  country,  a  wind  of  not 
less  than  15  miles  an  hour  may  generally 
be  expected  to  prevail  for  about  one-third  of 
the  year,  whilst  for  about  half  the  year  it  will 
be  10  miles  and  over ;  but  it  is  often  below 
the  latter  velocity  for  from  3  to  5  days, 
and  occasionally  a  week.  These  points,  how- 
ever, can  only  be  satisfactorily  elucidated  by 
local  observations.  Wind  engines,  when  lightly 
loaded,  will  run  with  a  breeze  of  less  than  10 
miles  an  hour,  but  as  the  power  of  wind  varies 
as  the  cube  of  its  velocity,  their  performance 
would  be  exceedingly  small.  For  the  same 
reason  the  great  increase  of  power  due  to 
winds  of  a  higher  velocity  than  about  20 
miles  an  hour  has  usually  to  be  run  to  waste. 
The  modern  wind  engine  has,  relatively,  more 
than  twice  as  much  sail  area  as  a  four-armed 
windmill,  but  it  only  runs  at  about  half  the 
speed,  so  that  the  surface  is  used  to  less 
advantage.  Owing,  however,  to  its  low  speed, 
the  vanes  of  a  wind  wheel  may  be  set  at  a 
much  greater  angle  with  the  plane  of  its 
revolution,  and  this,  coupled  with  the  large 
sail  area,  gives  it  a  much  higher  starting 
''torque,"  and  enables  it  to  work  in  lighter 
winds  than  would  suffice  for  the  old-fashioned 
mill.  In  a  good  breeze,  the  power  of  either 
type,  diameter  for  diameter,  is  much  the 
same.  The  proportions  of  four-armed  wind- 
mills vary  considerably,  but  the  following 
represents  good  practice.  The  breadth  of  the 
sweep  is  usually  about  one-fifth  of  its  radius, 
which  is  commonly  from  30  ft.  to  40  ft. ;  the 
sail  surface,  in  the  direction  of  its  length,  is 
generally  divided  in  the  proportion  of  three 
to  one  by  the  "  whip "  or  radial  arm,  the 
narrow  portion  moving  foremost.  The 
"  weather "  angle  of  the  inner  end  of  the 
wide  part  varies  from  20°  to  25°  with  the 


plane  of  motion  according  to  the  length  of 
the  sail ;  in  some  cases  the  angle  gradually 
diminishes  until  it  becomes  about  7°  at  the 
outer  extremity,  but  with  cloth  sails,  to  avoid 
flapping  (and  often  with  shuttered  sweeps), 
the  tip  is  made  to  coincide  with  the  plane 
of  motion.  In  this  case  the  sail  rapidly 
hollows  inwards  from  the  tip  in  order  that 
an  effective  angle  may  be  reached  as  soon  as 
possible.  The  "  lead,"  or  narrow  portion  of 
the  sail,  usually  preserves  throughout  its 
length  the  same  angle  as  the  inner  end  of 
the  sail.  The  best  tip  speed  is  about  two-and- 
a-half  times  that  of  the  wind,  and  in  a  15 
mile  wind  each  75  ft.  of  sail  surface  should 
give  about  1  h.p.  actual,  and  assuming  that 
the  speed  ratio  of  the  sails  to  the  wind  may 
remain  constant,  the  power  will  increase  nearly 
as  the  cube  of  the  wind  velocity.  The  wind 
wheel  has  its  vanes  arranged  in  an  annulus, 
and  their  combined  area  is  generally  from 
60  to  70  %  of  the  total  disc  surface.  The 
weather  angle  of  the  vanes  varies  from  30°  to 
40°,  and  is  often  uniform  throughout  their 
length.  To  produce  1  h.p.  in  a  15  mile 
wind  from  110  ft.  to  130  ft.  of  sail  surface  is 
required  according  to  the  design  and  size  of 
the  mill — the  larger  sizes  being  less  efficient. 
The  usual  method  of  speed  control  is  to  allow 
the  wheel  to  turn  more  or  less  obliquely  to 
the  wind  according  to  its  pressure ;  this  is 
accomplished  by  a  hinged  rudder  or  tail  vane 
which  is  maintained  at  right  angles  to  the 
plane  of  the  wheel  by  a  weighted  lever  or 
spring.  The  axis  of  the  wheel  is  parallel  to, 
but  not  in  line  with,  the  rudder,  so  that,  but 
for  the  action  of  the  weighted  lever,  the  wheel 
would  throw  out  of  the  wind.  Large  wheels 
are  usually  regulated  by  altering  the  weather- 
ing of  the  vanes,  automatically  or  otherwise, 
which  are  hinged  for  that  purpose.  (See 
"ANEMOMETER.")  E.  L.  B. 

Zinc. — Zinc  is  one  of  the  metallic  chemical 
elements,  found  to  a  limited  extent  in  England 
as  zinc  sulphide,  called  "zinc  blende"  or 
"  black  jack."  The  metal  is  usually  extracted 
by  the  Belgian  process  as  follows :  —  The 


558 


ZIN 


MUNICIPAL   AND   SANITARY  ENGINE  BEING. 


ZYM 


mixed    ore    and   coal   are   put   into    fireclay 
cylinders  of  about  8  in.   diameter  and  3  ft. 
long,  closed  at  one  end ;  from  40  to  80  of 
these  cylinders  are  ranged  in  a  furnace  like 
gas  retorts.     The  carbon  of  the  coal  unites 
with  the  oxide  of   the  zinc   and  escapes   as 
carbonic  oxide,  leaving  the  metallic  zinc  to 
come  off  as   a  dense  vapour.     This   is   con- 
densed in  cast-iron  conical  tubes,  from  which 
it  is  raked  out  into  a  large  iron  ladle ;    the 
zinc  is  then  skimmed  from  the  dross  and  cast 
into  ingots  of  70  Ibs.  to  80  Ibs.  each.     Zinc  is 
pliable  and  moderately  soft ;  at  a  temperature 
of  200°  to  250°  F.  it  is  rendered  malleable, 
and  may  be  rolled  into  thin  sheets.     For  this 
purpose  the  crude  ingots  are  re-melted  and 
cast  into  purer  ingots  of  convenient  size  for 
rolling   and   passed   between   cast-iron   rolls. 
Sheet  zinc  is  extensively  employed  for  cheap 
gutters,  small  rain-water  pipes,  lining  wood 
cisterns,  and  covering  flat  roofs.     It  resists 
the  action  of  pure  air  and  moisture,  but  the 
air  of  towns,  being  heavily  charged  with  acids, 
acts  freely  upon  it  and  destroys  it  rapidly.     It 
has  one  serious  defect  for  roofs,  as  it  blazes 
fiercely    under    the    action    of    fire.      Zinc, 
although   supposed  to  be  very  light,  weighs 
the  same  as  cast  iron — a  square  foot  1  in.  thick 
weighs  37£  Ibs.     There  is  a  zinc  gauge  differ- 
ing from  the  standard  gauge,  and  still  some- 
times used:  No.  12  Z.G.,  '025  in.  thick,  is 
used  for  flashings  ;  No.  14,  *031  in.  thick,  for 
dormers  and  flats ;  No.  16,  '041  in.  thick,  for 
gutters.     Zinc   when   alloyed   with  twice   its 
weight  of  copper  forms  yellow  brass,  but  zinc 
enters  into  the  composition  of  many  alloys  in 
the  bronze  series  as  well  as  the  brass  series. 
The  terms  "  higher  "  and  "  lower  "  applied  to 
brass  express  the  greater  or  less  quantity  of 
zinc  in  the  composition.     The  effect  of  zinc  in 
an  alloy  in  small  quantity  is  to  increase  the 
fusibility  without  reducing  the  hardness,  in 
larger  quantity  it  increases  the  malleability 
when  cold,  but  entirely  prevents  forging  when 
hot ;  1  to  2  %  of  zinc  enables  sounder  cast- 
ings to  be  made.    Zinc  is  brittle  when  cold,  and 
again  at  400°  F.,  but  it  is  malleable  at  212°  F. 
Galvanised    iron    is    sheet   iron,   corrugated 


or  plain,  coated  with  zinc  by  immersing 
it,  when  thoroughly  cleansed,  into  a  bath  of 
melted  zinc  covered  with  powdered  sal 
ammoniac.  Galvanised  iron  forms  a  cheap 
covering  for  the  sides  and  roofs  of  sheds,  and 
is  very  largely  used  in  new  countries.  The 
sheets  are  6  or  8  ft.  long,  3  ft.  2  in.  wide 
before  corrugation,  2  ft.  6  in.  wide  with  5  in. 
corrugations,  and  the  depth  of  corrugation  is 
a  quarter  of  the  width.  It  is  laid  with  6  in. 
laps  when  on  the  slope,  3  in.  when  vertical. 
No.  16  standard  gauge  is  the  thickness  used 
where  great  strength  is  required,  17  to  19  for 
first-class  work  generally,  20  to  22  for  ordinary 
work,  23  to  26  with  3  in.  flutes  for  shipping 
abroad.  H.  A. 

Zinc  Oxide  (known  as  Zinc  White). — A 
valuable  pigment  used  in  paint.  It  owes  its 
increasing  use  to  the  fact  that  it  is  non-toxic 
and  is  not  susceptible  to  the  influence  of 
sulphur  compounds,  as  white  lead  is.  It  is  a 
pure  white,  is  very  durable,  and  has  a  large 
covering  capacity  when  ground  in  oil.  (See 
"  PAINTS  AND  PAINTING.") 

Zones  of  Supply. — A  term  used  to 
indicate  different  levels  or  areas  of  pressure  in 
the  distribution  of  water.  In  districts  of  a 
very  undulating  character  it  sometimes 
becomes  necessary  to  limit  the  water  pressures 
in  the  supply  mains  in  the  lower  parts  of  the 
town  and  at  the  same  time  to  adopt  means  of 
augmenting  those  in  the  more  elevated  areas, 
thus  creating  "  zones  of  pressure  or  supply," 
each  being  adjusted  to  the  requirements  of  the 
portion  of  the  district  served.  (See  "  WATER 
SUPPLY.") 

Zymotic  Diseases.— After  Pasteur's  dis- 
covery of  the  anthrax  bacillus,  and  his 
demonstration  that  it  was  the  specific  cause 
of  anthrax  in  man  and  animals,  bacteriologists 
directed  attention  to  certain  other  diseases, 
and  it  has  since  been  ascertained  that  many 
of  these  are  due  to  the  infection  of  the  system 
by  micro-organisms.  There  are  still  others  so 
closely  allied  in  character  to  those  known  to 


559 


ZYM 


ENCYCLOPAEDIA   OF 


ZYM 


be  caused  by  bacteria  that  there  can  be  little 
doubt  that  they  are  due  to  a  similar  cause, 
but  as  yet  the  specific  germ  has  not  been 
discovered.  Originally  all  such  diseases  were 
termed  "  zymotic,"  but  of  recent  years  there 
has  been  a  tendency  to  abandon  the  term 
altogether  or  to  restrict  its  use  to  the  more 
acute  specific  fevers.  The  zymotic  death-rate 
is  still  recorded  by  medical  officers  of  health, 
and  signifies  the  annual  number  of  deaths  per 
1,000  population  from  the  seven  principal 
zymotic  diseases,  which  are  small-pox,  diph- 
theria, scarlet  fever,  measles,  whooping  cough, 
typhoid  (q.  v.\  and  allied  fevers  and  epidemic 
diarrhoea. 

Other  zymotic  diseases  are  cholera  (q.  r.), 
influenza,  plague,  cerebro-spinal  fever,  German 
measles,  mumps,  erysipelas,  yellow  fever, 
tetanus,  glanders,  syphilis,  gonorrhoea, 
leprosy,  pneumonia,  and  tuberculosis.  There 
are  many  others,  such  as  rheumatic  fever, 
which  are  almost  certainly  due  to  infec- 
tion by  micro-organisms,  though  absolute 
proofs  are  yet  wanting.  Certain  of  these 
diseases  are  notifiable.  The  Infectious 
Disease  (Notification)  Act,  1889,  imposes  an 
obligation  upon  medical  men  to  notify  to  the 
local  medical  officer  of  health  certain  cases  of 
infectious  disease  which  occur  in  his  practice 
as  soon  as  he  becomes  aware  that  the  patient 
is  suffering  from  such  disease.  The  diseases  so 
notifiable  are  scarlet  fever,  diphtheria,  small- 
pox, cholera,  fevers  (typhoid,  typhus,  continued 
and  puerperal),  and  erysipelas  ;  but  measles, 
chicken-pox,  phthisis,  and  other  diseases  may 
be  scheduled  by  a  local  authority  after  certain 
formalities  and  with  the  consent  of  the  Local 
Government  Board.  It  is  now  fully  recog- 
nised that  these  diseases  are  not  caused  by 
insanitary  conditions.  Such  conditions  greatly 
predispose  persons  living  within  their  sphere 
of  influence  to  attack,  by  reducing  the  vitality 
or  disease-resisting  power  of  the  system,  but 
unless  the  specific  germ  of  a  disease  is  present 
and  in  some  way  gains  an  entrance  into  the 
system  that  disease  will  not  supervene. 
Where  filth  is  prevalent,  where  overcrowding 
abounds,  and  especially  where  these  are 

560 


associated  with  poverty,  the  possibility  of  the 
germs  of  disease  gaining  access  to  the  system 
is  enormously  increased,  and  it  is  the  preva- 
lence of  zymotic  diseases  under  such  condi- 
tions that  has  led  many  to  conclude  that  they 
are  the  only  condition  necessary  for  the 
causation  of  certain  fevers.  The  subjoined 
table  gives  the  death-rates  per  1,000  popula- 
tion from  all  causes  and  from  the  principal 
zymotic  diseases,  including  phthisis,  for  the 
last  three  completed  decennia  : — 


1S61-VO. 

1S71-S1. 

1881-91. 

1S91-1900. 

All  causes 

22-4 

21'3 

19.1 

18-2 

Small-pox 

•16 

•23 

•04 

•006 

Measles 

•44 

•39 

•44 

•41 

Scarlet  fever  .  . 

•93 

•72 

•33 

•16 

Diphtheria     .  . 

•18 

•12 

•16 

•26 

Whooping  cough 

•53 

•51 

•45 

•38 

Fevers 

•88 

•48 

•24 

•25 

Typhoid  fever 

— 

•32 

•20 

•17 

Diarrhceal  diseases  . 

1-06 

•94 

•67 

•73 

Phthisis 

2'5 

2-1 

1-7 

1-4 

It  will  be  observed  that  measles  and  diph- 
theria show  no  signs  of  decreasing  ;  obviously, 
therefore,  sanitary  improvements  have  had  no 
influence  upon  them,  or  if  there  has  been  any 
effect  it  is  so  masked  by  the  other  factors, 
such  as  enforced  school  attendance,  as  to  be 
unrecognisable.  The  decreased  prevalence  of 
small-pox  is  chiefly  attributable  to  the  con- 
tinued practice  of  vaccination.  Scarlet  fever 
mortality  has  decreased  so  rapidly  and  steadily 
that  we  might  conclude  improved  sanitary 
conditions  and  the  provision  of  isolation 
hospitals  have  had  a  most  marked  effect,  but 
there  are  reasons  for  doubting  whether  such 
is  the  case.  The  type  of  the  disease  has  been 
undergoing  a  continuous  diminution  in  viru- 
lency,  so  that,  although  as  many  cases  occur  as 
heretofore,  the  mortality  has  fallen  enormously. 
It  is  possible,  however,  that  the  more  clean  con- 
ditions which  obtain  and  the  isolation  of  the 
more  severe  cases  have  had  a  share  in 
diminishing  the  virulency.  That  fevers  have 
decreased  to  one-fourth  is  due  to  the  greater 
attention  paid  to  supplies  of  milk,  water, 
and  articles  of  food,  to  the  diminution  of 


ZYM 


MUNICIPAL   AND   SANITARY  ENGINEERING. 


ZYM 


overcrowding,  the  demolition  of  slums,  and  the 
erection  of  workmen's  dwellings,  and  to  im- 
proved methods  of  sewerage  and  drainage. 
The  reduction  in  the  death-rate  from 
diarrhceal  diseases  may  be  due  to  the  same 
causes,  but  as  very  young  children  are  the 
chief  sufferers,  and  the  mortality  varies  very 
largely  from  year  to  year  according  to  the 
earth-temperature  in  the  autumn,  it  is  obvious 
that  there  are  conditions,  of  which  we  are  as 
yet  ignorant,  which  influence  the  mortality 
from  these  diseases.  The  cause  of  the  great 
and  continuous  decrease  in  the  mortality  from 
phthisis  is  one  of  the  enigmas  of  public 
health.  The  drying  of  the  subsoil  by  the 
sewerage  of  towns,  the  prevention  of  damp  in 
houses  by  enforcing  proper  building  by-laws, 
are  possibly  important  factors.  Small-pox, 
measles,  scarlet  fever,  diphtheria,  whooping 
cough,  and  typhus  fever  are  diseases  which 
are  spread  by  the  inhalation  of  the  breath  of 
infected  persons  and  by  the  inhalation  of 
minute  particles  of  sputum  discharged  by 
infected  persons  when  coughing.  The  infec- 
tion of  typhus  fever  and  small-pox  also 
appears  to  be  capable  of  being  given  off  from 
the  skin.  Obviously,  therefore,  there  is  less 
danger  of  these  diseases  being  disseminated  in 
roomy  and  well  ventilated  houses  than  in  small 
badly  ventilated  and  overcrowded  dwellings. 

Outbreaks  of  scarlet  fever,  typhoid  fever, 
and  diphtheria  have  frequently  been  traced  to 
milk,  though  how  the  milk  became  infected 
has  not  always  been  discovered.  Generally, 
however,  it  has  been  found  that  some  person 
suffering  from  one  of  these  diseases  has  been 
employed  in  the  cowsheds  or  dairy  from  which 
the  implicated  milk  was  derived, 


Typhoid  fever  and  cholera  are  chiefly  water- 
borne  diseases,  but  any  article  of  food  may 
become  infected,  and  convey  the  diseases. 
The  germs  of  these  diseases  are  chiefly  voided 
in  the  stools,  and  in  typhoid  fever  the  patient's 
urine  often  swarms  with  the  specific  bacteria. 
Hence  the  great  danger  arising  from  the  use 
of  privies  and  pail  closets,  of  water-closets 
without  proper  flushing  apparatus,  from 
accumulation  of  house  refuse  and  from  defec- 
tive paving  around  yard  gullies.  Infection 
under  such  circumstances  may  easily  be 
conveyed  by  flies  or  by  wind  to  exposed 
articles  of  food,  and  spread  of  the  disease 
results. 

It  is  fortunate  for  the  human  race  that  the 
mere  presence  of  a  few  of  these  germs  in  the 
system  rarely  suffices  to  set  up  disease, 
otherwise  man  would  have  been  exterminated 
long  ago.  The  blood  possesses  certain 
germicidal  powers,  and  when  vitality  is 
unimpaired,  germs  entering  the  system,  if 
not  in  excessive  number,  may  be  destroyed. 
Where  it  is  necessary  for"  the  microbes  to 
gain  access  to  the  blood  stream  before  they 
can  produce  any  evil  effects  it  is  quite  possible 
for  them  to  pass  through  the  alimentary  canal 
and  fail  to  enter  the  system.  The  blood  also 
possesses  to  some  extent  the  power  of  destroying 
the  toxins  or  poisonous  bodies  formed  during 
the  growth  of  disease-producing  bacteria. 
These  properties  explain  why,  when  large 
numbers  of  persons  partake  of  specifically 
infected  water  or  milk,  only  a  small  propor- 
tion, as  a  rule,  are  actually  attacked  by 
disease.  (Vide  "  GERMS  OF  DISEASE.") 

J.  C.  T, 


M.S.E. 


561 


o  o 


A  LIST  OF  BOOKS 

ON 


ADAMS,  JULIUS  W.  Sewers  and  Drains  for  Populous  Districts  with 
Rules  and  Formulas  for  the  Determination  of  their  Dimensions 
under  All  Circumstances.  Xinth  Edition.  Illustrated.  8vo.,  cloth, 
236  pp.  New  York,  1902 $2 . 50 

BAKER,  M.  N.  British  Sewage  Works  and  Notes  on  the  Sewage  Farms 
of  Paris  and  on  Two  German  Works.  8vo.,  cloth,  150  pp.  New 
York,  1904 ' $2.00 

Sewerage  and  Sewage  Purification.  Fourth  Edition,  revised  and 

enlarged.  16mo.,  boards,  101  pp.  (Van  Nostrand  Science  Series 
No.  18.)  New  York,  1907 50  cents 

BARWISE,  SIDNEY.  The  Purification  of  Sewage.  Being  a  Brief  Account 
of  the  Scientific  Principles  of  Sewage  Purification  and  Their  Appli- 
cation. Second  Edition,  revised.  Illustrated.  Svo.,  cloth,  220  pp. 
New  York,  1904 Net,  $3.50 

DIBDIN,  W.  J.  The  Purification  of  Sewage  and  Water.  Third  Edition, 
revised  and  enlarged.  Illustrated.  8vo.,  cloth,  415  pp.  New 
York,  1903 $3.50 

DUNBAR,  Dr.  Principles  of  Sewage  Treatment.  Translated  by  H.  T. 
Calvert,  147  Illustrations.  8vo.,  cloth,  304  pp.  London 
1908 Net  $4.5o 

FOLWELL,  A-  PRESCOTT.  The  Designing,  Construction,  and  Mainte- 
nance of  Sewerage  Systems.  Fifth  Edition,  revised  and  enlarged. 
Illustrated.  8vo.,  cloth,  469  pp.  New  York,  1908 $3'.00 

FOWLER,  GILBERT  J.  Sewage  Works  Analysis.  Illustrated.  12mo.; 
cloth,  143  pp.  New  York,  1902 $2 .00 


GERHARD,  W.  P.  The  Disposal  of  Household  Wastes.  Second  Edition 
Illustrated.  16mo.,  boards,  195  pp.  (Van  Nostrand  Science 
Series  No.  97.)  New  York,  1904 50  cents 

The   Sanitation,   Water   Supply,   and   Sewage   Disposal   of   Country 

Houses.      Illustrated.       12mo.,      cloth,      346      pp.      New     York 
1909 Net,    $2.00 

MARTIN,  ARTHUR  J.  The  Sewage  Problem :  A  Review  of  the  Evidence 
Collected  by  the  Royal  Commission  on  Sewage  Disposal.  12mo., 
cloth,  379pp.  London,  1905 Net,  $3.50 

MERRIMAN,  M.  Elements  of  Sanitary  Engineering.  Third  Edition,  re- 
vised and  enlarged.  Illustrated.  8vo.,  cloth,  250  pp.  New 
York,  1906 , Net,  $2.00 

MOORE,  E.  C.  S.  and  SILCOCK,  E.  J.  Sanitary  Engineering.  Third 
Edition,  revised  and  rewritten.  Two  volumes.  920  illustrations. 
8vo.,  cloth,  900  pp  Philadelphia,  1910 Net  $14.00 

OGDEN,  H.  N.  Sewer  Construction.  192  Illustrations.  8vo.,  cloth, 
347  pp.  New  York,  1908 $3.00 

Sewer  Design.     54  Illustrations.     5  Plates.     12mo.,  cloth,  245  pp. 

New  York,  1907 $2 .00 

RAFTER,  GEORGE  W.  The  Treatment  of  Septic  Sewage.  Second  Edition. 
16mo.,  boards,  140  pp.  (Van  Nostrand  Science  Series  No.  118.) 
New  York,  1907 50  cents 

RAFTER,  G.  W.,  and  BAKER,  M.  N.  Sewage  Disposal  in  the  United 
States.  116  Illustrations.  8vo.,  cloth,  598  pp.  New  York.  .$6 .00 

RAIKES,  HUGH  P.  The  Design,  Construction,  and  Maintenance  of  Sew- 
age Disposal  Works.  Being  a  Practical  Guide  to  Modern  Methods 
of  Sewage  Purification.  72  Illustrations.  8vo.,  cloth,  430  pp. 
New  York,  1908 Net,  $4 .00 

RIDEAL,  SAMUEL.  Sewage  and  Bacterial  Purification  of  Sewage. 
Third  Edition,  enlarged.  58  Illustrations.  8vo.,  cloth,  367  pp. 
New  York,  1907 $4.00 


SCOBLE,  HERBERT  T.  Land  Treatment  of  Sewage:  A  Digest  of  the 
Reports  made  to  the  Royal  Commission  on  Sewage  Disposal  by 
their  Specially-appointed  Officers.  4to.,  cloth,  80  pp.  London 
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SLATER,  J.  W.  Sewage  Treatment,  Purification  and  Utilization.  Illus- 
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STALEY,  C.,  and  PIERSON,  G.  S.  The  Separate  System  of  Sewerage:  Its 
Theory  and  Construction.  Third  Edition,  revised  and  enlarged,  with 
a  chapter  on  Sewage  Disposal.  Illustrated.  8vo.,  cloth,  336  pp. 
New  York,  1899 $3 .00 

THUDICHUM,  G.  Simple  Methods  of  Testing  Sewage  Effluents  for  Works 
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1905 Net,  $1 .00 

VENABLE,  W.  M.  Methods  and  Devices  for  Bacterial  Treatment  of  Sew- 
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VERNON-HARCOURT,  L.  F.  Sanitary  Engineering  with  Respect  to  Water 
Supply  and  Sewage  Disposal.  287  Illustrations.  8vo.,  cloth,  419 
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WANKLYN,  J.  A.,  and  COOPER,  W.  J.  Sewage  Analysis.  A  Practical 
Treatise  on  the  Examination  of  Sewage  and  the  Effluents  from  Sew- 
age. Illustrated.  12mo.,  cloth,  230pp.  London,  1899. .  Net,  $2.00 

WARING,  GEO.  E.  Modern  Methods  of  Sewage  Disposal  for  Towns,  Pub- 
lic Institutions  and  Isolated  Houses.  Third  Edition.  Illustrated. 
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A  PRACTICAL  TREATISE  ON 


RELATING    TO 

Hydrology,  jlyflroflpamlcs,  and  to  me  Practical  Consiniction  of 
Water-Works,  ID  Honti  America. 

WITH    NUriEROUS 

and  Illti^trdtion^f. 

BY 

J.    T.    FANNING,    C.    E., 

MEMBER  OF  THE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS. 


SECTION  I — Collection  and  Storage  of  Water,  and  its  Impurities. 

Chapter  I. — Introductory.  Chap.  n. — Quantity  of  Water  Required.  Chap.  III. — Rainfall. 
Chap.  IV. — Flow  of  Streams.  Chap.  V. — Storage  and  Evaporation  of  Water.  Chap.  VI. — 
Supplying  Capacity  of  Watersheds.  Chap.  VII. — Springs  and  Wells.  Chap.  VTTJ. — Impurities 
of  Water.  Chap.  IX. — Well,  Spring,  Lake,  and  River  Supplies. 

SECTION  II.— Flow  of  Water  through  Sluices,  Pipes,  and  Channels. 

Chap.  X. — Weight,  Pressure,  and  Motion  of  Water.  Chap.  XI. — Flow  of  Water  through 
Orifices.  Chap.  XII.— Flow  of  Water  through  Short  Tubes.  Chap.  XIII.— Flow  of  Water 
through  Pipes  under  Pressure.  Chap.  XIV.— Measuring  Weirs  and  Weir  Guaging.  Chap.  XV. — 
Flow  of  Water  in  Open  Channels. 

SECTION  III — Practical  Construction  of  Water- Works. 

Chap.  XVI. — Reservoir  Embankments  and  Chambers.  Chap.  XVII. — Open  Canals.  Chap 
XVm.— Waste  Weirs.  Chap.  XIX.— Partitions  and  Retaining  Walls.  Chap.  XX.— Masonry 
Conduits.  Chap.  XXI. — Mains  and  Distribution  Pipes.  Chap.  XXII.— Distribution  Systems, 
and  Appendages.  Chap.  XXIII.— Clarification  of  Water.  Chap.  XXIV.— Pump?.ng  of  Water 
Chap.  XXV.— Tank  Stand  Pipes.  Chap.  XXVI.— Systems  of  Water  Supply. 

Appendix.— Miscellaneous  Memoranda.      INDEX. 


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Contents 


Alternative  methods  of  Treatment  and  Preliminary  Considera- 
tions Affecting  the  Design  and  Construction  of  Works.  Diffusion  in 
Tidal  Waters.  Irrigation  and  Land  Filtration.  Removal  of  Matters 
in  Suspension  by  Screening  and  Treatment  in  Tanks.  Chemical 
Precipitants  and  the  Disposal  of  Sewage  Sludge.  Filtering  Media 
for  Bacteria  Beds.  Contact  Beds  and  their  Operation.  Percolating 
Filters,  Alternative  Methods  of  Construction  and  Working.  Distri- 
bution over  Percolating  Filters.  The  Separation  and  Disposal  of 
Storm  Water.  Purification  of  Trade  Wastes.  Maintenance  and 
Management  of  Sewage  Disposal  Works.  Index. 


IN  view  of  the  fadl  that  many  millions  of  dollars  are  spent  annually  on  Sewage 
Disposal  Works,  it  is  obviously   a   matter  of  the  greatest  importance,  in  the 
interests  both  of  economy  and  of  public  health,  that  those  who  are  entrusted 
with  the  design  and  construction  of  such  works,  or  with  the  expenditure  of  public 
money  upon  them,  should  not  only  clearly  understand  the  essential  principles  involved, 
but  should  also  have  at  their  disposal  the  latest  results  of  contemporary  experience  to 
guide  them  in  the  practical  application  of  those  principles. 

Although  the  chemical  and  biological  aspects  of  Sewage  Disposal  have  been  very 
fully  dealt  with  by  a  number  of  writers,  there  is  no  up-to-date  book  from  which 
equally  full  and  reliable  information  can  be  obtained  regarding  the  more  practical  side 
of  the  question,  considered  from  the  point  of  view  of  the  engineer. 

In  attempting  to  make  good  this  deficiency,  the  author  of  the  present  book  has 
presented  an  impartial  review  of  the  modem  methods  of  sewage  purification,  on  the 
practical  application  of  which  he  has  been  engaged  for  the  past  fifteen  years.  We 
can,  without  hesitation,  highly  recommend  this  book  to  all  engineers  interested  in  this 
important  and  timely  subject. 


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PURIFICATION 


OF 


SEWAGE  AND  WATER 


BY 


W.  J.   DIBDIN, 

r.  i.  c.,  r.  c  s. 


CONTENTS 

Preface.  Introduction.  Chapter  I.— General  Considerations. 
Chapter  II.— Antiseptics,  or  Preservation  for  Limited  Periods.  Bacter- 
iological Methods.  Chapter  III.— Precipitation.  Chapter  IV.— Experi- 
ments at  Massachusetts  and  London.  Chapter  V.— Sutton  Experi- 
ments. Chapter  VI  —The  Septic  Tank  and  Other  Systems.  Chapter 
VII.— Land  Treatment  Versus  Bacteria  Beds.  Chapter  VIII.— Manches- 
ter Experiments.  Chapter  IX.— Leeds  Experiments.  Chapter  X.— The 
Bacterial  Treatment  of  Factory  Refuse.  Chapter  XI  —Screening. 
Chapter  XII.— The  Purification  of  the  Thames.  Chapter  XIII,— The 
Discharge  of  Sewage  into  Sea-Water.  Chapter  XIV.— The  Filtration 
of  Potable  Water.  Chapter  XV.— Systematic  Examination  of  Potable 
Water.  Chapter  XVI.— The  Character  of  the  London  Water  Supply. 
Chapter  XVII.— The  Action  of  Soft  Water  upon  Lead.  Chapter 
XVIII.— The  Absorption  of  Atmospheric  Oxygen  by  Water.  Chapter 
XIX.— Analyses  and  their  Interpretation.  Chapter  XX.— Ventilation 
and  Deodorisation  of  Sewers.  Chapter  XXI.— The  Royal  Commission 
on  Sewage  Disposal.  Appendix  I.— Examination  for  Matters  in 
Supension.  Appendix  II.— Dissolved  Oxygen.  Index.— List  of  Illus- 
trations, Diagrams  and  Tables. 


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Diagrams.  Price  $3.5O  Net* 

THE  PURIFICATION 
Op 

BEING 

A  Brief  Account  of  the  Scientific  Principles  of  Sewage  Purification 
and  their  Practical  Application 

BY 

SIDNEY  BARWISE,  M.  D.  (Lond.)  B.  Sc. 

M.R.C.S.,  D.P.H.  (CAMB.) 
Fellow  of  the  Sanitary  Institute,  Medical  Officer  of  Health,  Derbyshire  County  Council. 

With  an  Appendix  on  the  Analysis  of  Sewage  and  Sewage  Effluents, 

CONTENTS. 

CHAPTER  I— Sewage;  Its  Nature  and  Composition. 

CHAP.  II— The  Chemistry  of  Sewage. 

CHAP.  III.— Varieties  of  Sewage  and  the  Changes  it  Undergoes. 

CHAP.  IV— River  Pollution  and  its  Effects. 

CHAP.  V.—The  Land  Treatment  of  Sewage. 

CHAP.  VI. — Precipitation,  Precipitants,  and  Tanks. 

CHAP.  VII— The  Liquefaction  of  Sewage. 
CHAP.  VIII. — Principles  Involved  on  the  Oxidation  of  Sewage. 

CHAP.  IX.— Artificial  Processes  of  Purification. 

CHAP.  JC. — Automatic  Distributors  and  Special  Filters. 

CHAP.  XI.— Conclusion. 

APPENDIX. 
ON    THE    ANALYSIS    OF    SEWAGE    AND    SEWAGE    EFFLUENTS. 

CHAP.  I. —  77/i?  Apparatus  Required  for  Sewage  Analysis. 
CHAP.  II. — Standard  Solutions   Used  in  and  Methods  of  Sewage  Analysis. 

INDEX. 

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WORKS  BY  WH.  PAUL  GERHARD.  C.  E. 

HOUSE  DRAINAGE  AND  SANITARY  PLUMBING.  Twelfth  Edition, 
1  908.  Illustrated.  23  1  pages.  1  8mo.  Price,  bound  in  boards, 
50  cents.  (Science  Series  No.  63). 

"Eminently  practical  and  comprehends  more  valuable  information  on  the 
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"  It  is  one  of  the  best  summaries  of  house  drainage  and  sanitary  plumbing 
hitherto  published."  —  The  Sanitarian. 

RECENT  PRACTICE  IN  THE  SANITARY  DRAINAGE  OF  BUILDINGS. 

Second  Edition,  1  890.  1  75  pages.  1  8mo.  Price  bound  in  boards, 
50  cents.  (Science  Series  No.  93.)  Forms  Supplement  to  No.  63. 

Contains  Maxims  of  Plumbing  and  House  Drainage,  a  Complete  Plumbing 
Specification,  also  Memoranda  on  the  Cost  of  Plumbing  Work  and  Sugges- 
tions for  a  Sanitary  Code. 

THE  DISPOSAL  OF  HOUSEHOLD  WASTES.  Second  Edition.  1904. 
Illustrated.  1  95  pages.  1  8mo.  Bound  in  boards,  price,  50  cents. 
(Science  Series  No.  97). 

A  discussion  of  the  best  methods  of  treatment  of  the  sewage  of  farm  houses, 
isolated  country  houses,  suburban  dwellings,  houses  in  villages  and  small 
towns,  and  of  institutions,  such  as  hospitals,  asylums,  prisons,  hotels,  etc.,  also 
of  modes  of  removal  and  disposal  of  garbage,  ashes  and  other  house  refuse. 

GAS  LIGHTING  AND  GAS  FITTING.  Third  Edition,  1904.  190  pages. 

1  8mo.  Bound  in  boards,  price  50  cents.  (Science  Series  No  111.) 

A  Pocketbook  for  Gas  Companies,  Gas  Engineers,  Gas  Fitters,  Manufac- 
turers of  Gas  Appliances,  Gas  Consumers,  Builders,  Architects,  and  Munici- 
pal Inspectors.  Contains  Hints  to  Gas  Consumers. 

THE  SANITATION,  WATER  SUPPLY,  AND  SEWAGE 
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